NNAT

Gene Summary

Gene:NNAT; neuronatin
Aliases: Peg5
Location:20q11.2-q12
Summary:The protein encoded by this gene is a proteolipid that may be involved in the regulation of ion channels during brain development. The encoded protein may also play a role in forming and maintaining the structure of the nervous system. This gene is found within an intron of the BLCAP gene, but on the opposite strand. This gene is imprinted and is expressed only from the paternal allele. Two transcript variants encoding two different isoforms have been found for this gene. [provided by RefSeq, Nov 2009]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:neuronatin
HPRD
Source:NCBIAccessed: 20 August, 2015

Ontology:

What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 20 August 2015 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 20 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: NNAT (cancer-related)

Liu S, Yin F, Zhang J, et al.
Regulatory roles of miRNA in the human neural stem cell transformation to glioma stem cells.
J Cell Biochem. 2014; 115(8):1368-80 [PubMed] Related Publications
To investigate the expressional alternation of microRNAs (miRNA) during the malignant transformation and development of human glioma, we measured miRNA expression profile as well as mRNA expression profile in normal human neural stem cells (hNSCs) and human glioma stem cells (hGSCs). We found 116 miRNA up-regulated and 62 miRNA down-regulated in GSCs. On the other hand, we identified 1,372 mRNA down-regulated, and 1,501 mRNA up-regulated in GSCs compared to those in NSCs. We then analyzed the pathways and the predicted target genes of the miRNAs which differ significantly in expression between GSCs and NSCs using the statistical enrichment methods. These target mRNAs are involved in many cancer-related signaling pathways, such as cell cycle, axon guidance, glioma development, adhesion junction, MAPK and Wnt signaling. Furthermore, we obtained the differently expressed miRNA-target relationships according to the θ value which is used to calculate the regulation extent of miRNA-target and using the databases of miRanda, Targetscans and Pictar. Among the top 10 miRNA-target relationships, hsa-miR-198 and its potential targeted gene DCX and NNAT were selected for validation, and NNAT was found to be the direct target of miR-198. Finally, the functional roles of miR-155-5p and miR-124-3p whose expressions altered significantly between GSCs and NSCs were addressed. Our results provide new clues for the potential mechanisms involved in the origin and development of glioma. Clinically, the altered miRNAs may serve as potential targets and diagnostic tools for novel therapeutic strategies of glioblastoma.

Joseph RM
Neuronatin gene: Imprinted and misfolded: Studies in Lafora disease, diabetes and cancer may implicate NNAT-aggregates as a common downstream participant in neuronal loss.
Genomics. 2014 Feb-Mar; 103(2-3):183-8 [PubMed] Related Publications
Neuronatin (NNAT) is a ubiquitous and highly conserved mammalian gene involved in brain development. Its mRNA isoforms, chromosomal location, genomic DNA structure and regulation have been characterized. More recently there has been rapid progress in the understanding of its function in physiology and human disease. In particular there is fairly direct evidence implicating neuronatin in the causation of Lafora disease and diabetes. Neuronatin protein has a strong predisposition to misfold and form cellular aggregates that cause cell death by apoptosis. Aggregation of Neuronatin within cortical neurons and resulting cell death is the hallmark of Lafora disease, a progressive and fatal neurodegenerative disease. Under high glucose conditions simulating diabetes, neuronatin protein also accumulates and destroys pancreatic beta cells. The neuronatin gene is imprinted and only the paternal allele is normally expressed in the adult. However, changes in DNA methylation may cause the maternal allele to lose imprinting and trigger cell proliferation and metastasis. Neuronatin has also been shown to be translated peripherally within the dendrites of neurons, a finding of relevance in synaptic plasticity. The current understanding of the function of neuronatin raises the possibility that this gene may participate in the common downstream mechanisms associated with aberrant neuronal growth and death. A better understanding of these mechanisms may open new therapeutic targets to help modify the progression of devastating neurodegenerative conditions such as Alzheimer's and anterior horn cell disease.

Renner M, Wolf T, Meyer H, et al.
Integrative DNA methylation and gene expression analysis in high-grade soft tissue sarcomas.
Genome Biol. 2013; 14(12):r137 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: High-grade soft tissue sarcomas are a heterogeneous, complex group of aggressive malignant tumors showing mesenchymal differentiation. Recently, soft tissue sarcomas have increasingly been classified on the basis of underlying genetic alterations; however, the role of aberrant DNA methylation in these tumors is not well understood and, consequently, the usefulness of methylation-based classification is unclear.
RESULTS: We used the Infinium HumanMethylation27 platform to profile DNA methylation in 80 primary, untreated high-grade soft tissue sarcomas, representing eight relevant subtypes, two non-neoplastic fat samples and 14 representative sarcoma cell lines. The primary samples were partitioned into seven stable clusters. A classification algorithm identified 216 CpG sites, mapping to 246 genes, showing different degrees of DNA methylation between these seven groups. The differences between the clusters were best represented by a set of eight CpG sites located in the genes SPEG, NNAT, FBLN2, PYROXD2, ZNF217, COL14A1, DMRT2 and CDKN2A. By integrating DNA methylation and mRNA expression data, we identified 27 genes showing negative and three genes showing positive correlation. Compared with non-neoplastic fat, NNAT showed DNA hypomethylation and inverse gene expression in myxoid liposarcomas, and DNA hypermethylation and inverse gene expression in dedifferentiated and pleomorphic liposarcomas. Recovery of NNAT in a hypermethylated myxoid liposarcoma cell line decreased cell migration and viability.
CONCLUSIONS: Our analysis represents the first comprehensive integration of DNA methylation and transcriptional data in primary high-grade soft tissue sarcomas. We propose novel biomarkers and genes relevant for pathogenesis, including NNAT as a potential tumor suppressor in myxoid liposarcomas.

Li X, Li D, Zhuang Y, et al.
Overexpression of miR-708 and its targets in the childhood common precursor B-cell ALL.
Pediatr Blood Cancer. 2013; 60(12):2060-7 [PubMed] Related Publications
BACKGROUND: The critical function of microRNAs in the pathogenesis and prognosis of hematopoietic cancer has become increasingly apparent. However, only a few miRNAs have been reported to be altered in acute lymphocytic leukemia (ALL).
PROCEDURES: To uncover aberrantly expressed miRNAs in pediatric B-cell ALL, our study employed genome-wide miRNA microarray analysis and stem-loop real-time quantitative polymerase chain reaction (qRT-PCR) to examine common precursor B-cell ALL samples. The target genes of miRNA-708 were then identified and verified by bioinformatics, dual-luciferase reporter assay, qRT-PCR, and Western blot.
RESULTS: Significant upregulation of miR-708, miR-210, and miR-181b, and downregulation of miR-345 and miR-27a were observed in common precursor B-cell ALL (common-ALL) samples (P < 0.05). In addition, elevated expression of miR-708 and miR-181b were found in high-risk common-ALL compared to standard and intermediate ones. miR-708 inhibited luciferase reporter activity by binding to the 3'-untranslated regions (3'-UTRs) of CNTFR, NNAT, and GNG12 mRNA in HEK-293 cell line and suppressed the protein levels of CNTFR, NNAT, and GNG12 in Jurkat cells. In addition, mRNA levels of CNTFR and NNAT, but not of GNG12, were found to be downregulated in high risk common-ALL samples. Mutational analysis revealed that miR-708 binds to the 394-400 bp sequence region of the 3'-UTR of CNTFR mRNA.
CONCLUSION: The expression level of miR-708 reflects differences among the clinical types of common-ALL, and CNTFR, NNAT, and GNG12 were identified as targets of miR-708.

Hubertus J, Zitzmann F, Trippel F, et al.
Selective methylation of CpGs at regulatory binding sites controls NNAT expression in Wilms tumors.
PLoS One. 2013; 8(6):e67605 [PubMed] Free Access to Full Article Related Publications
Aberrant expression of imprinted genes, such as those coding for the insulin-like growth factor 2 (IGF2) and neuronatin (NNAT), is a characteristic of a variety of embryonic neoplasms, including Wilms tumor (WT). In case of IGF2, it is generally accepted that loss of imprinting in a differentially methylated region of the IGF2/H19 locus results in biallelic expression and, thus, upregulation of the gene. In this study we examined methylation pattern at potential regulatory elements of the paternally expressed NNAT gene in a cohort of WT patients in order to further characterize the molecular mechanism causing overexpression of this regulatory gene. We demonstrate that transcriptional upregulation of NNAT in WT is grossly independent of the bladder cancer-associated protein (BLCAP) gene, an imprinted gene within the imprinted domain of the NNAT locus. However, expression of the BLCAP transcript isoform v2a formerly known to be selectively expressed from the paternal allele in brain was associated with high expression of NNAT. This contrasts the situation we found at the IGF2/H19 locus, which shows high overexpression of IGF2 and inversely correlated expression of the H19 gene in WT. An analysis of DNA methylation in two potential regulatory regions of the NNAT locus by pyrosequencing revealed significant hypomethylation of the tumors compared to normal kidney tissue. Interestingly, the difference in DNA methylation was highest at CpGs that were observed within three putative binding sites of the CCCTC-binding factor CTCF. Most importantly, hypomethylation of both NNAT regulatory regions is significantly associated with the upregulation of NNAT expression and the BLCAP_v2a transcript. Our data indicate that the methylation status of a not-yet-described regulatory element within the NNAT locus that contains four potential CTCF binding sites determines the expression level of NNAT and the nearby located BLCAP_v2a transcript, thereby suggesting a functional role in the aberrant upregulation of NNAT in WT.

Vidal AC, Murphy SK, Murtha AP, et al.
Associations between antibiotic exposure during pregnancy, birth weight and aberrant methylation at imprinted genes among offspring.
Int J Obes (Lond). 2013; 37(7):907-13 [PubMed] Free Access to Full Article Related Publications
OBJECTIVES: Low birth weight (LBW) has been associated with common adult-onset chronic diseases, including obesity, cardiovascular disease, type II diabetes and some cancers. The etiology of LBW is multi-factorial. However, recent evidence suggests exposure to antibiotics may also increase the risk of LBW. The mechanisms underlying this association are unknown, although epigenetic mechanisms are hypothesized. In this study, we evaluated the association between maternal antibiotic use and LBW and examined the potential role of altered DNA methylation that controls growth regulatory imprinted genes in these associations.
METHODS: Between 2009-2011, 397 pregnant women were enrolled and followed until delivery. Prenatal antibiotic use was ascertained through maternal self-report. Imprinted genes methylation levels were measured at differentially methylated regions (DMRs) using bisulfite pyrosequencing. Generalized linear models were used to examine associations among antibiotic use, birth weight and DMR methylation fractions.
RESULTS: After adjusting for infant gender, race/ethnicity, maternal body mass index, delivery route, gestational weight gain, gestational age at delivery, folic acid intake, physical activity, maternal smoking and parity, antibiotic use during pregnancy was associated with 138 g lower birth weight compared with non-antibiotic use (β-coefficient=-132.99, s.e.=50.70, P=0.008). These associations were strongest in newborns of women who reported antibiotic use other than penicillins (β-coefficient=-135.57, s.e.=57.38, P=0.02). Methylation at five DMRs, IGF2 (P=0.05), H19 (P=0.15), PLAGL1 (P=0.01), MEG3 (P=0.006) and PEG3 (P=0.08), was associated with maternal antibiotic use; among these, only methylation at the PLAGL1 DMR was also associated with birth weight.
CONCLUSION: We report an inverse association between in utero exposure to antibiotics and lower infant birth weight and provide the first empirical evidence supporting imprinted gene plasticity in these associations.

Nestheide S, Bridge JA, Barnes M, et al.
Pharmacologic inhibition of epigenetic modification reveals targets of aberrant promoter methylation in Ewing sarcoma.
Pediatr Blood Cancer. 2013; 60(9):1437-46 [PubMed] Related Publications
BACKGROUND: Ewing sarcoma (ES), a highly aggressive tumor of children and young adults, is characterized most commonly by an 11;22 chromosomal translocation that fuses EWSR1 located at 22q12 with FLI1, coding for a member of the ETS family of transcription factors. Although genetic changes in ES have been extensively researched, our understanding of the role of epigenetic modifications in this neoplasm is limited.
PROCEDURE: In an effort to improve our knowledge in the role of epigenetic changes in ES we evaluated the in vitro antineoplastic effect of the DNA methyltransferase inhibitor 5-Aza-deoxycytidine (5-Aza-dC) and identified epigenetically silenced genes by pharmacologic unmasking of DNA methylation coupled with genome-wide expression profiling.
RESULTS: Comparisons between untreated and 5-Aza-dC treated ES cell lines (n = 5) identified 208 probe sets with at least twofold difference in expression (P ≤ 0.05). The 208 probe sets represented 145 upregulated and 31 down-regulated genes. Of the 145 genes upregulated after 5-Aza-dC treatment, four: were further characterized. ACRC, CLU, MEST, and NNAT were found to be hypermethylated and transcriptionally down-regulated in ES cell lines. Further studies revealed that ACRC, CLU, MEST, and NNAT were often hypermethylated in primary ES tumors. Transfection-mediated reexpression of ACRC, CLU, MEST, and NNAT in ES cell lines resulted in decreased growth in culture.
CONCLUSIONS: This study demonstrated epigenetically modified genes in ES cell lines and primary tumors and suggested that epigenetic dysregulation may contribute to disease pathogenesis in ES.

Ryu S, McDonnell K, Choi H, et al.
Suppression of miRNA-708 by polycomb group promotes metastases by calcium-induced cell migration.
Cancer Cell. 2013; 23(1):63-76 [PubMed] Related Publications
The progression of cancer to metastatic disease is a major cause of death. We identified miR-708 being transcriptionally repressed by polycomb repressor complex 2-induced H3K27 trimethylation in metastatic breast cancer. miR-708 targets the endoplasmic reticulum protein neuronatin to decrease intracellular calcium level, resulting in reduction of activation of ERK and FAK, decreased cell migration, and impaired metastases. Ectopic expression of neuronatin refractory to suppression by miR-708 rescued cell migration and metastasis defects. In patients with breast cancer, miR-708 expression was decreased in lymph node and distal metastases, suggesting a metastasis-suppressive role. Our findings uncover a mechanistic role for miR-708 in metastasis and provide a rationale for developing miR-708 as a therapeutic agent against metastatic breast cancer.

Kaushal M, Mishra AK, Sharma J, et al.
Genomic alterations in breast cancer patients in betel quid and non betel quid chewers.
PLoS One. 2012; 7(8):e43789 [PubMed] Free Access to Full Article Related Publications
Betel Quid (BQ) chewing independently contributes to oral, hepatic and esophageal carcinomas. Strong association of breast cancer risk with BQ chewing in Northeast Indian population has been reported where this habit is prodigal. We investigated genomic alterations in breast cancer patients with and without BQ chewing exposure. Twenty six BQ chewers (BQC) and 17 non BQ chewer (NBQC) breast cancer patients from Northeast India were analyzed for genomic alterations and pathway networks using SNP array and IPA. BQC tumors showed significantly (P<0.01) higher total number of alterations, as compared with NBQC tumors, 48 ± 17% versus 32 ± 25 respectively. Incidence of gain in fragile sites in BQC tumors were significantly (P<0.001) higher as compared with NBQC tumors, 34 versus 23% respectively. Two chromosomal regions (7q33 and 21q22.13) were significantly (p<0.05) associated with BQC tumors while two regions (19p13.3-19p12 and 20q11.22) were significantly associated with NBQC tumors. GO terms oxidoreductase and aldo-keto reductase activity in BQC tumors in contrast to G-protein coupled receptor protein signaling pathway and cell surface receptor linked signal transduction in NBQC tumors were enriched in DAVID. One network "Drug Metabolism, Molecular Transport, Nucleic Acid Metabolism" including genes AKR1B1, AKR1B10, ETS2 etc in BQC and two networks "Molecular Transport, Nucleic Acid Metabolism, Small Molecule Biochemistry" and "Cellular Development, Embryonic Development, Organismal Development" including genes RPN2, EMR3, VAV1, NNAT and MUC16 etc were seen in NBQC. Common alterations (>30%) were seen in 27 regions. Three networks were significant in common regions with key roles of PTK2, RPN2, EMR3, VAV1, NNAT, MUC16, MYC and YWHAZ genes. These data show that breast cancer arising by environmental carcinogens exemplifies genetic alterations differing from those observed in the non exposed ones. A number of genetic changes are shared in both tumor groups considered as crucial in breast cancer progression.

Hubertus J, Lacher M, Rottenkolber M, et al.
Altered expression of imprinted genes in Wilms tumors.
Oncol Rep. 2011; 25(3):817-23 [PubMed] Related Publications
Overexpression of insulin-like growth factor 2 (IGF2), an imprinted gene located on chromosome 11p15, has been reported as a characteristic feature in various embryonal tumors, including Wilms tumor (WT). Recent studies specified loss of imprinting (LOI) in a differential methylated region (DMR) of the IGF2/H19 cluster or loss of heterozygosity (LOH), respectively, uniparental disomy (UPD) being responsible for this overexpression. However, the role of other imprinted genes in the genesis of WT is still unknown. In the current study, we analyzed transcriptional activity of the imprinted genes IGF2, H19, NNAT, DLK1, RTL1, MEG3, and MEST as well as the methylation status of the DMR of the IGF2/H19 cluster in a panel of 32 WTs. Except for H19, we detected massive overexpression of all genes in the majority of WTs compared to normal renal tissue, which was most prominent for the paternally expressed genes IGF2, NNAT, and MEST. Alterations of the H19DMR were found in two-thirds of the WTs. Moreover, we have seen a strong correlation between the transcriptional activity of IGF2, NNAT and MEST and LOI/LOH of H19DMR, which was inverse for H19. Expression of DLK1, RTL1 and MEG3 does not correlate with LOI/LOH of H19DMR. Altogether, our findings suggest that over-expression of imprinted genes is common in WTs and correlates at least for some imprinted genes with LOI of H19DMR. Thus, it may be speculated that alterations of the DNA modification machinery drive erroneous setting of methylation marks in imprinting regions throughout the genome, which leads to the concomitant activation of imprinted genes in blastomagenesis.

Waldmann J, Fendrich V, Holler J, et al.
Microarray analysis reveals differential expression of benign and malignant pheochromocytoma.
Endocr Relat Cancer. 2010; 17(3):743-56 [PubMed] Related Publications
The diagnosis of a malignant pheochromocytoma (PC) can only be established by the presence of distant metastases, but a subset of apparently benign PCs develop metastases. We have employed a microarray analysis to identify a typical gene expression profile which distinguishes malignant from benign PC. Total RNA was isolated from fresh-frozen tissue of five benign and five malignant PCs. The reference consisted of laser microdissected tissue from normal adrenal medulla. After generating Cy3- and Cy5-fluorescently labeled cDNAs, F-chips containing 11 540 spots were hybridized. Data were analyzed with the IMAGENE 3.0 software. Gene expression levels were validated by real-time (RT)-PCR and immunohistochemistry (IHC). The analysis revealed a more than twofold difference in expression between benign and malignant PCs in 132 genes: 19 were up-regulated and 113 were down-regulated. Expression differences of six genes (calsequestrin, NNAT, neurogranin, secreted protein acidic and rich in cysteine (SPARC), EGR2, and MAOB) were confirmed by RT-PCR in 25 PCs. IHC for calsequestrin revealed an overexpression in malignant PCs (7/10 vs 1/10, P=0.03). Comparative analysis by microarray of all ten PCs (benign/malignant) versus normal adrenal medulla revealed a more than twofold expression difference in 455/539 and 491/671 genes respectively. Several of these genes are known to participate on adrenal tumorigenesis, potential tumor suppressor genes, and oncogenes. Comprehensive gene expression analysis of malignant and benign PCs revealed different gene profiles, which could be used to discriminate between malignant and benign PCs. Based on these findings, the strategy for further follow-up and treatment could be modified accordingly.

Ye Q, Wang TF, Peng YF, et al.
Expression of alpha-, beta- and gamma-synuclein in colorectal cancer, and potential clinical significance in progression of the disease.
Oncol Rep. 2010; 23(2):429-36 [PubMed] Related Publications
The synucleins (alpha-, beta- and gamma-synuclein) are a small, soluble, highly conserved group of neuronal proteins that attracted considerable attention due to their involvement in both neurodegenerative diseases and cancer. In this study, we examined the synuclein exprsssion in colorectal cancer (CRC) tissues, tumor-matched non-neoplastic adjacent tissues (NNAT), and CRC cell lines, and then investigated clinical significance of synucleins. By using semi-quantitative RT-PCR, synuclein mRNA expression was detected in eight CRC cell lines. It was much higher in CRC samples than in NNAT samples (P<0.05). The results of western blotting showed that the levels of synucleins protein expression in CRC cells approximately corresponded to the levels of synuclein mRNA expression. Immunohistochemical staining revealed that gamma-synuclein protein expression was up-regulated in CRC samples compared to NNAT samples (P=0.022), and was significantly correlated with clinical stage and lymph node involvement of CRC (P<0.05). Although, there was no significant difference in either alpha- or beta-synuclein protein expression between tumor and normal samples (P>0.05), often more than one form of synuclein was expressed in a tumor sample. More ratios of later stage and lymph node-positive tumors expressed a least one type of synuclein protein, and more ratios showed positive for either alpha or gamma-synuclein expression, as well as positive either for beta or gamma-synuclein in more ratios of lymph node-positive tumors. These results show that alpha-, beta- and gamma-synuclein are expressed in a high percentage of CRC. gamma-synuclein protein is valuable for evaluation of progression of CRC, and it is more sensitive to predict advanced stage and lymph node invasion by detection of gamma-synuclein protein combined with either alpha- or beta-synuclein protein or both than by detection of gamma-synuclein only.

Ye Q, Feng B, Peng YF, et al.
Expression of gamma-synuclein in colorectal cancer tissues and its role on colorectal cancer cell line HCT116.
World J Gastroenterol. 2009; 15(40):5035-43 [PubMed] Free Access to Full Article Related Publications
AIM: To investigate the expression pattern of gamma-synuclein in colorectal cancer (CRC) tissues, and to study the effects of gamma-synuclein on CRC cell line HCT116 biological features in vitro.
METHODS: The expression pattern of gamma-synuclein was determined in 54 CRC tissues and 30 tumor-matched nonneoplastic adjacent tissues (NNAT) 5 cm away from the tumor via real-time quantitative reverse transcription PCR (RT-PCR) and immunohistochemistry. The relationship between gamma-synuclein protein expression and clinicopathological factors of CRC tissues was analyzed. Three small interfering RNA (siRNA) targeting gamma-synuclein mRNA plasmids were constructed and transfected into the CRC cell line HCT116. The stable cell lines were selected with G-418 for 28 d, and the biological features of these cells were examined by cell growth curve, soft agar assay, and cell migration and invasion assays in vitro.
RESULTS: The expression of gamma-synuclein mRNA and protein was much higher in CRC tissue samples than in NNAT samples (P = 0.02, P = 0.036). There was a significant correlation between the gamma-synuclein protein expression and clinical stage and lymph node involvement of CRC (P = 0.02, P = 0.033). In functional analysis we found that down-regulation of gamma-synuclein expression in HCT116 cells could inhibit the growth, colony formation rate, and migration and invasion ability of HCT116 cells.
CONCLUSION: Increased expression of gamma-synuclein in CRC tissues and the biological effects of reduced gamma-synuclein expression on HCT116 cells suggest that gamma-synuclein may play a positive role in the progression of CRC.

Revill K, Dudley KJ, Clayton RN, et al.
Loss of neuronatin expression is associated with promoter hypermethylation in pituitary adenoma.
Endocr Relat Cancer. 2009; 16(2):537-48 [PubMed] Related Publications
The imprinted gene, neuronatin (NNAT), is one of the most abundant transcripts in the pituitary and is thought to be involved in the development and maturation of this gland. In a recent whole-genome approach, exploiting a pituitary tumour cell line, we identified hypermethylation associated loss of NNAT. In this report, we determined the expression pattern of NNAT in individual cell types of the normal gland and within each of the different pituitary adenoma subtypes. In addition, we determined associations between expression and CpG island methylation and used colony forming efficiency assays (CFE) to gain further insight into the tumour-suppressor function of this gene. Immunohistochemical (IHC) co-localization studies of normal pituitaries showed that each of the hormone secreting cells (GH, PRL, ACTH, FSH and TSH) expressed NNAT. However, 33 out of 47 adenomas comprising, 11 somatotrophinomas, 10 prolactinomas, 12 corticotrophinomas and 14 non-functioning tumours, irrespective of subtype failed to express either NNAT transcript or protein as determined by quantitative real-time RT-PCR and IHC respectively. In normal pituitaries and adenomas that expressed NNAT the promoter-associated CpG island showed characteristics of an imprinted gene where approximately 50% of molecules were densely methylated. However, in the majority of adenomas that showed loss or significantly reduced expression of NNAT, relative to normal pituitaries, the gene-associated CpG island showed significantly increased methylation. Induced expression of NNAT in transfected AtT-20 cells significantly reduced CFE. Collectively, these findings point to an important role for NNAT in the pituitary and perhaps tumour development in this gland.

Ye Q, Zheng MH, Cai Q, et al.
Aberrant expression and demethylation of gamma-synuclein in colorectal cancer, correlated with progression of the disease.
Cancer Sci. 2008; 99(10):1924-32 [PubMed] Related Publications
Recent evidence suggests that gamma-synuclein is abnormally expressed in a high percentage of tumor tissues of diversified cancer types, but rarely expressed in tumor-matched non-neoplastic adjacent tissues (NNAT). The molecular mechanism of CpG island demethylation may underlie aberrant gamma-synuclein expression. To fully understand the roles of aberrant gamma-synuclein expression and demethylation in the development of colorectal cancer (CRC), we examined the expression and methylation status of gamma-synuclein in 67 CRC samples, 30 NNAT samples, and five CRC cell lines as well. By using reverse transcription-polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry analyses, gamma-synuclein expression was detected in both HT-29 and HCT116 cells, and was much higher in CRC samples than in NNAT samples (P < 0.05). The demethylating agent, 5-aza-2 cent-deoxycytidine, can induce re-expression of gamma-synuclein in COLO205, LoVo, and SW480 cells. Unmethylated gamma-synuclein alleles were detected in HT-29, HCT116, and LoVo cells by nested methylation-specific PCR, and the demethylated status of gamma-synuclein was much higher in CRC samples than in NNAT samples by real-time quantitative methylation-specific PCR (P < 0.05). The results of genomic bisulfite DNA sequencing further confirmed that the aberrant gamma-synuclein expression in CRC was primarily attributed to the demethylation of CpG island. The protein expression and demethylation status of gamma-synuclein in 67 CRC samples correlated with clinical stage, lymph node involvement, and distant metastasis. These findings suggest an involvement of aberrant gamma-synuclein expression and demethylation in progression of CRC, especially in advanced stages.

Dudley KJ, Revill K, Whitby P, et al.
Genome-wide analysis in a murine Dnmt1 knockdown model identifies epigenetically silenced genes in primary human pituitary tumors.
Mol Cancer Res. 2008; 6(10):1567-74 [PubMed] Related Publications
DNA methylation at promoter CpG islands (CGI) is an epigenetic modification associated with inappropriate gene silencing in multiple tumor types. In the absence of a human pituitary tumor cell line, small interfering RNA-mediated knockdown of the maintenance methyltransferase DNA methyltransferase (cytosine 5)-1 (Dnmt1) was used in the murine pituitary adenoma cell line AtT-20. Sustained knockdown induced reexpression of the fully methylated and normally imprinted gene neuronatin (Nnat) in a time-dependent manner. Combined bisulfite restriction analysis (COBRA) revealed that reexpression of Nnat was associated with partial CGI demethylation, which was also observed at the H19 differentially methylated region. Subsequent genome-wide microarray analysis identified 91 genes that were significantly differentially expressed in Dnmt1 knockdown cells (10% false discovery rate). The analysis showed that genes associated with the induction of apoptosis, signal transduction, and developmental processes were significantly overrepresented in this list (P < 0.05). Following validation by reverse transcription-PCR and detection of inappropriate CGI methylation by COBRA, four genes (ICAM1, NNAT, RUNX1, and S100A10) were analyzed in primary human pituitary tumors, each displaying significantly reduced mRNA levels relative to normal pituitary (P < 0.05). For two of these genes, NNAT and S100A10, decreased expression was associated with increased promoter CGI methylation. Induced expression of Nnat in stable transfected AtT-20 cells inhibited cell proliferation. To our knowledge, this is the first report of array-based "epigenetic unmasking" in combination with Dnmt1 knockdown and reveals the potential of this strategy toward identifying genes silenced by epigenetic mechanisms across species boundaries.

Siu IM, Bai R, Gallia GL, et al.
Coexpression of neuronatin splice forms promotes medulloblastoma growth.
Neuro Oncol. 2008; 10(5):716-24 [PubMed] Free Access to Full Article Related Publications
Medulloblastoma (MB) is the most common pediatric brain cancer. Several important developmental pathways have been implicated in MB formation, but fewer therapeutic targets have been identified. To locate frequently overexpressed genes, we performed a comprehensive gene expression survey of MB. Our comparison of 20 primary tumors to normal cerebellum identified neuronatin (NNAT) as the most frequently overexpressed gene in our analysis. NNAT is a neural-specific developmental gene with alpha and beta splice forms. Functional evaluation revealed that RNA interference knockdown of NNAT causes a significant decrease in proliferation. Conversely, coexpression of both splice forms in NNAT-negative MB cell lines increased proliferation, caused a significant shift from G(1) to G(2)/M, and increased soft agar colony formation and size. When expressed individually, each NNAT splice form had much less effect on these in vitro oncogenic predictors. In an in vivo model, the coexpression of both splice forms conferred the ability of xenograft formation to human MB cells that do not normally form xenografts, whereas a control gene had no effect. Our findings suggest that the frequently observed overexpression of both NNAT splice forms in MB enhances growth in this cancer.

Yamashita S, Takahashi S, McDonell N, et al.
Methylation silencing of transforming growth factor-beta receptor type II in rat prostate cancers.
Cancer Res. 2008; 68(7):2112-21 [PubMed] Related Publications
To identify methylation-silenced genes in prostate cancers, a microarray analysis for genes up-regulated by treatment with a demethylating agent, 5-aza-2'-deoxycytidine, was performed using three rat prostate cancer cell lines. Eight genes (Aebp1, Dysf, Gas6, LOC361288, Nnat, Ocm, RGD1308119, and Tgfbr2) were re-expressed at 16-fold or more, and their promoter CpG islands were shown to be densely methylated in the cancer cell lines. From the eight genes, Tgfbr2, a key mediator of transforming growth factor-beta (TGF-beta) signaling that has been strongly implicated in human and rat prostate carcinogenesis, was selected, and its silencing in primary samples was analyzed further. Tgfbr2 was methylated and markedly down-regulated in three of seven 3,2'-dimethyl-4-aminobiphenyl-induced invasive adenocarcinomas in the dorsolateral lobe of the rat prostate. In humans, marked down-regulation of TGFBR2 protein was observed in 12 of 20 high-grade prostatic intraepithelial neoplasia and 36 of 60 prostate cancers. DNA methylation of the human TGFBR2 promoter CpG islands repressed transcription, if present, but neither methylation nor mutation were detected in 27 human prostate cancers analyzed. Methylation silencing of rat Tgfbr2 was associated with histone H3 lysine 9 trimethylation, whereas decreased expression of human TGFBR2 was mainly due to decreased transcription activity, sometimes in concert with histone deacetylation and H3 lysine 27 trimethylation. The identification of methylation silencing of Tgfbr2 in rat prostate cancers, in accordance with TGFBR2 down-regulation in human prostate cancers, will enable us to analyze how aberrant methylation is induced in vivo and identify factors that promote and suppress the induction of aberrant methylation.

Uchihara T, Okubo C, Tanaka R, et al.
Neuronatin expression and its clinicopathological significance in pulmonary non-small cell carcinoma.
J Thorac Oncol. 2007; 2(9):796-801 [PubMed] Related Publications
INTRODUCTION: Neuronatin is a protein that is specifically expressed in the nervous system in the course of embryonal brain development, and its expression is limited to the pituitary gland in normal human adults. Neuronatin expression has been reported in some types of tumor. The purpose of this study was to clarify the significance of neuronatin expression in pulmonary non-small cell carcinoma.
METHODS: We determined the frequency of neuronatin expression in surgically resected samples from non-small cell lung carcinoma (51 adenocarcinoma and 41 squamous cell carcinoma) by immunohistochemical staining, and investigated the correlations between expression level and various clinicopathological features.
RESULTS: Expression of neuronatin was observed more frequently in squamous cell carcinoma (63%) than in adenocarcinoma (25%). In most cases, nontumorous lung tissue did not react with the antibody against neuronatin. In both adenocarcinoma and squamous cell carcinoma, less differentiated tumors expressed neuronatin more frequently than did differentiated tumors. In adenocarcinoma, but not squamous cell carcinoma, the prognosis of neuronatin-positive cases was significantly worse than that of neuronatin-negative cases.
CONCLUSION: Neuronatin expression is specific for tumor tissue and was detected in both pulmonary adenocarcinoma and squamous cell carcinoma at high frequency, particularly in less differentiated tumors. Neuronatin expression is associated with poor prognosis in patients with adenocarcinoma, and may be useful as a prognostic marker for lung adenocarcinoma.

Higashi M, Tajiri T, Kinoshita Y, et al.
High expressions of neuronatin isoforms in favorable neuroblastoma.
J Pediatr Hematol Oncol. 2007; 29(8):551-6 [PubMed] Related Publications
Neuroblastoma is a malignant solid tumor of children, which derives from the embryonal sympathoadrenal linage. Clinical cases can vary widely from a favorable to an unfavorable prognosis according to the presence of genetic aberrations, such as MYCN amplification. Our cDNA microarray analysis which compared the gene expressions between favorable and unfavorable neuroblastomas showed a high expression of the neuronatin (Nnat) gene in favorable neuroblastomas. Nnat is highly conserved in mammalian species, and its expression appears in nervous systems from the hindbrain to the peripherals during the prenatal periods. The Nnat mRNA expression, investigated in 63 of neuroblastoma samples by quantitative reverse-transcription polymerase chain reaction, was found to be significantly higher in the favorable prognosis groups than in the unfavorable groups. Nnat is an imprinted gene, and its expression in IMR32 neuroblastoma cell line was up-regulated by treatment with a demethylating agent. High expressions of Nnat isoforms induced in an IMR32 neuroblastoma cell line changed the cell morphology to the extension of the neural processes, which thus indicated the occurrence of cell differentiation. In conclusion, the high expressions of Nnat were found to be associated with good prognoses in neuroblastoma, which might indicate tumor differentiation, and its suppressions in unfavorable tumors are considered to be under epigenetic control.

Okubo C, Minami Y, Tanaka R, et al.
Analysis of differentially expressed genes in neuroendocrine carcinomas of the lung.
J Thorac Oncol. 2006; 1(8):780-6 [PubMed] Related Publications
INTRODUCTION: Large cell neuroendocrine carcinoma (LCNEC) and small cell lung carcinoma (SCLC) show considerable differences in their histology but share neuroendocrine (NE) characteristics and also genetic and/or expression patterns.
METHODS: We used the subtractive expression method to identify differences in gene expression that would allow discrimination between these two types of NE lung carcinoma.
RESULTS: Eight cDNA fragments were transcribed at a higher level in LCNEC compared with SCLC, and these corresponded to five mitochondrial genes, two ribosomal genes, and one fetal regulation factor, neuronatin (NNAT). Immunohistochemically, NNAT protein was detected in 43% (6/14) of LCNECs but in only 8% (1/13) of SCLCs (p < 0.05). Positive staining for NNAT was observed in areas that did not show the NE morphology, such as palisading and rosettes.
CONCLUSIONS: The present results suggest that NNAT has the potential to be used as a differential maker between LCNEC and SCLC.

Cheng PN, Lam TL, Lam WM, et al.
Pegylated recombinant human arginase (rhArg-peg5,000mw) inhibits the in vitro and in vivo proliferation of human hepatocellular carcinoma through arginine depletion.
Cancer Res. 2007; 67(1):309-17 [PubMed] Related Publications
Hepatocellular carcinoma (HCC) is believed to be auxotrophic for arginine through the lack of expression of argininosuccinate synthetase (ASS). The successful use of the arginine-depleting enzyme arginine deiminase (ADI) to treat ASS-deficient tumors has opened up new possibilities for effective cancer therapy. Nevertheless, many ASS-positive HCC cell lines are found to be resistant to ADI treatment, although most require arginine for proliferation. Thus far, an arginine-depleting enzyme for killing ASS-positive tumors has not been reported. Here, we provide direct evidence that recombinant human arginase (rhArg) inhibits ASS-positive HCCs. All the five human HCC cell lines we used were sensitive to rhArg but ADI had virtually no effect on these cells. They all expressed ASS, but not ornithine transcarbamylase (OTC), the enzyme that converts ornithine, the product of degradation of arginine with rhArg, to citrulline, which is converted back to arginine via ASS. Transfection of HCC cells with OTC resulted in resistance to rhArg. Thus, OTC expression alone may be sufficient to induce rhArg resistance in ASS-positive HCC cells. This surprising correlation between the lack of OTC expression and sensitivity of ASS-positive HCC cells shows that OTC-deficient HCCs are sensitive to rhArg-mediated arginine depletion. Therefore, pretreatment tumor gene expression profiling of ASS and OTC could aid in predicting tumor response to arginine depletion with arginine-depleting enzymes. We have also shown that the rhArg native enzyme and the pegylated rhArg (rhArg-peg(5,000mw)) gave similar anticancer efficacy in vitro. Furthermore, the growth of the OTC-deficient Hep3B tumor cells (ASS-positive and ADI-resistant) in mice was inhibited by treatment with rhArg-peg(5,000mw), which is active alone and is synergistic in combination with 5-fluorouracil. Thus, our data suggest that rhArg-peg(5,000mw) is a novel agent for effective cancer therapy.

Dannenberg LO, Edenberg HJ
Epigenetics of gene expression in human hepatoma cells: expression profiling the response to inhibition of DNA methylation and histone deacetylation.
BMC Genomics. 2006; 7:181 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: DNA methylation and histone deacetylation are epigenetic mechanisms that play major roles in eukaryotic gene regulation. We hypothesize that many genes in the human hepatoma cell line HepG2 are regulated by DNA methylation and histone deacetylation. Treatment with 5-aza-2'-deoxycytidine (5-aza-dC) to inhibit DNA methylation with and/or Trichostatin A (TSA) to inhibit histone deacetylation should allow us to identify genes that are regulated epigenetically in hepatoma cells.
RESULTS: 5-aza-dC had a much larger effect on gene expression in HepG2 cells than did TSA, as measured using Affymetrix HG-U133 Plus 2.0 microarrays. The expression of 1504 probe sets was affected by 5-aza-dC (at p < 0.01), 535 probe sets by TSA, and 1929 probe sets by the combination of 5-aza-dC and TSA. 5-aza-dC treatment turned on the expression of 211 probe sets that were not detectably expressed in its absence. Expression of imprinted genes regulated by DNA methylation, such as H19 and NNAT, was turned on or greatly increased in response to 5-aza-dC. Genes involved in liver processes such as xenobiotic metabolism (CYP3A4, CYP3A5, and CYP3A7) and steroid biosynthesis (CYP17A1 and CYP19A1), and genes encoding CCAAT element-binding proteins (C/EBPalpha, C/EBPbeta, and C/EBPgamma) were affected by 5-aza-dC or the combination. Many of the genes that fall within these groups are also expressed in the developing fetal liver and adult liver. Quantitative real-time RT-PCR assays confirmed selected gene expression changes seen in microarray analyses.
CONCLUSION: Epigenetics play a role in regulating the expression of several genes involved in essential liver processes such as xenobiotic metabolism and steroid biosynthesis in HepG2 cells. Many genes whose expression is normally silenced in these hepatoma cells were re-expressed by 5-aza-dC treatment. DNA methylation may be a factor in restricting the expression of fetal genes during liver development and in shutting down expression in hepatoma cells.

Dekel B, Metsuyanim S, Schmidt-Ott KM, et al.
Multiple imprinted and stemness genes provide a link between normal and tumor progenitor cells of the developing human kidney.
Cancer Res. 2006; 66(12):6040-9 [PubMed] Related Publications
Wilms' tumor (WT), the embryonic kidney malignancy, is suggested to evolve from a progenitor cell population of uninduced metanephric blastema, which typically gives rise to nephrons. However, apart from blastema, WT specimens frequently contain cells that have differentiated into renal tubular or stromal phenotypes, complicating their analysis. We aimed to define tumor-progenitor genes that function in normal kidney development using WT xenografts (WISH-WT), in which the blastema accumulates with serial passages at the expense of differentiated cells. Herein, we did transcriptional profiling using oligonucleotide microarrays of WISH-WT, WT source, human fetal and adult kidneys, and primary and metastatic renal cell carcinoma. Among the most significantly up-regulated genes in WISH-WT, we identified a surprising number of paternally expressed genes (PEG1/MEST, PEG3, PEG5/NNAT, PEG10, IGF2, and DLK1), as well as Meis homeobox genes [myeloid ecotropic viral integration site 1 homologue 1 (MEIS1) and MEIS2], which suppress cell differentiation and maintain self-renewal. A comparison between independent WISH-WT and WT samples by real-time PCR showed most of these genes to be highly overexpressed in the xenografts. Concomitantly, they were significantly induced in human fetal kidneys, strictly developmentally regulated throughout mouse nephrogenesis and overexpressed in the normal rat metanephric blastema. Furthermore, in vitro differentiation of the uninduced blastema leads to rapid down-regulation of PEG3, DLK1, and MEIS1. Interestingly, ischemic/reperfusion injury to adult mouse kidneys reinduced the expression of PEG3, PEG10, DLK1, and MEIS1, hence simulating embryogenesis. Thus, multiple imprinted and stemness genes that function to expand the renal progenitor cell population may lead to evolution and maintenance of WT.

Becker M, Sommer A, Krätzschmar JR, et al.
Distinct gene expression patterns in a tamoxifen-sensitive human mammary carcinoma xenograft and its tamoxifen-resistant subline MaCa 3366/TAM.
Mol Cancer Ther. 2005; 4(1):151-68 [PubMed] Related Publications
The reasons why human mammary tumors become resistant to tamoxifen therapy are mainly unknown. Changes in gene expression may occur as cells acquire resistance to antiestrogens. We therefore undertook a comparative gene expression analysis of tamoxifen-sensitive and tamoxifen-resistant human breast cancer in vivo models using Affymetrix oligonucleotide arrays to analyze differential gene expression. Total RNAs from the tamoxifen-sensitive patient-derived mammary carcinoma xenograft MaCa 3366 and the tamoxifen-resistant model MaCa 3366/TAM were hybridized to Affymetrix HuGeneFL and to Hu95Av2 arrays. Pairwise comparisons and clustering algorithms were applied to identify differentially expressed genes and patterns of gene expression. As revealed by cluster analysis, the tamoxifen-sensitive and the tamoxifen-resistant breast carcinomas differed regarding their gene expression pattern. More than 100 transcripts are changed in abundance in MaCa 3366/TAM as compared with MaCa 3366. Among the genes that are differentially expressed in the tamoxifen-resistant tumors, there are several IFN-inducible and estrogen-responsive genes, and genes known to be involved in breast carcinogenesis. The genes neuronatin (NNAT) and bone marrow stem cell antigen 2 (BST2) were sharply up-regulated in MaCa 3366/TAM. The differential expression of four genes (NNAT, BST2, IGFBP5, and BCAS1) was confirmed by Taqman PCR. Our results provide the starting point for deriving markers for tamoxifen resistance by differential gene expression profiling in a human breast cancer model of acquired tamoxifen resistance. Finally, genes whose expression profiles are distinctly changed between the two xenograft lines will be further evaluated as potential targets for diagnostic or therapeutic approaches of tamoxifen-resistant breast cancer.

Yokota N, Mainprize TG, Taylor MD, et al.
Identification of differentially expressed and developmentally regulated genes in medulloblastoma using suppression subtraction hybridization.
Oncogene. 2004; 23(19):3444-53 [PubMed] Related Publications
To increase our understanding of the molecular pathogenesis of medulloblastoma (MB), we utilized the technique of suppression subtractive hybridization (SSH) to identify genes that are dysregulated in MB when compared to cerebellum. SSH-enriched cDNA libraries from both human and Ptch+/- heterozygous murine MBs were generated by subtracting common cDNAs from corresponding non-neoplastic cerebellum. For the human classic MB library, total human cerebellar RNA was used as control tissue; for the Ptch+/- heterozygous MB, non-neoplastic cerebellum from an unaffected Ptch+/- littermate was used as the control. Through differential screening of these libraries, over 100 upregulated tumor cDNA fragments were isolated, sequenced and identified with the NCBI BLAST program. From these, we selected genes involved in cellular proliferation, antiapoptosis, and cerebellar differentiation for further analysis. Upregulated genes identified in the human MB library included Unc33-like protein (ULIP), SOX4, Neuronatin (NNAT), the mammalian homologue of Drosophila BarH-like 1(BARHL1), the nuclear matix protein NRP/B (ENC1), and the homeobox OTX2 gene. Genes found to be upregulated in the murine MB library included cyclin D2 (Ccnd2), thymopoietin (Tmpo), Musashi-1 (Msh1), protein phosphatase 2A inhibitor-2 (I-2pp2a), and Unc5h4(D). Using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), the mRNA expression levels for these genes were markedly higher in human MBs than in cerebellum. Western blot analysis was used to further confirm the overexpression of a subset of these genes at the protein level. Notch pathway overactivity was demonstrated in the TE671 MB cell line expressing high levels of MSH1 through HES1-Luciferase transfections. This study has revealed a panel of developmentally regulated genes that may be involved in the pathogenesis of MB.

Kursa M, Walker GF, Roessler V, et al.
Novel shielded transferrin-polyethylene glycol-polyethylenimine/DNA complexes for systemic tumor-targeted gene transfer.
Bioconjug Chem. 2003 Jan-Feb; 14(1):222-31 [PubMed] Related Publications
Tumor-targeting DNA complexes which can readily be generated by the mixing of stable components and freeze-thawed would be very advantageous for their subsequent application as medical products. Complexes were generated by the mixing of plasmid DNA, linear polyethylenimine (PEI22, 22 kDa) as the main DNA condensing agent, PEG-PEI (poly(ethylene glycol)-conjugated PEI) for surface shielding, and Tf-PEG-PEI (transferrin-PEG-PEI) to provide a ligand for receptor-mediated cell uptake. Within the shielding conjugates, PEG chains of varying size (5, 20, or 40 kDa) were conjugated with either linear PEI22 (22 kDa) or branched PEI25 (25 kDa). The three polymer components were mixed together at various ratios with DNA; particle size, surface charge, in vitro transfection activity, and systemic gene delivery to tumors was investigated. In general, increasing the proportion of shielding conjugate in the complex reduced surface charge, particle size, and in vitro transfection efficiency in transferrin receptor-rich K562 cells. The particle size or surface charge of the complexes containing the PEG-PEI conjugate did not significantly change after freeze-thawing, while complexes without the shielding conjugate aggregated. Complexes containing PEG-PEI conjugate efficiently transfected K562 cells after freeze-thawing. Furthermore the systemic application of freeze-thawed complexes exhibited in vivo tumor targeted expression. For complexes containing the luciferase reporter gene the highest expression was found in tumor tissue of mice. An optimum formulation for in vivo application, PEI22/Tf-PEG-PEI/PEI22-PEG5, containing plasmid DNA encoding for the tumor necrosis factor (TNF-alpha), inhibited tumor growth in three different murine tumor models. These new DNA complexes offer simplicity and convenience, with tumor targeting activity in vivo after freeze-thawing.

Li CM, Guo M, Borczuk A, et al.
Gene expression in Wilms' tumor mimics the earliest committed stage in the metanephric mesenchymal-epithelial transition.
Am J Pathol. 2002; 160(6):2181-90 [PubMed] Free Access to Full Article Related Publications
Wilms' tumor (WT) has been considered a prototype for arrested cellular differentiation in cancer, but previous studies have relied on selected markers. We have now performed an unbiased survey of gene expression in WTs using oligonucleotide microarrays. Statistical criteria identified 357 genes as differentially expressed between WTs and fetal kidneys. This set contained 124 matches to genes on a microarray used by Stuart and colleagues (Stuart RO, Bush KT, Nigam SK: Changes in global gene expression patterns during development and maturation of the rat kidney. Proc Natl Acad Sci USA 2001, 98:5649-5654) to establish genes with stage-specific expression in the developing rat kidney. Mapping between the two data sets showed that WTs systematically overexpressed genes corresponding to the earliest stage of metanephric development, and underexpressed genes corresponding to later stages. Automated clustering identified a smaller group of 27 genes that were highly expressed in WTs compared to fetal kidney and heterologous tumor and normal tissues. This signature set was enriched in genes encoding transcription factors. Four of these, PAX2, EYA1, HBF2, and HOXA11, are essential for cell survival and proliferation in early metanephric development, whereas others, including SIX1, MOX1, and SALL2, are predicted to act at this stage. SIX1 and SALL2 proteins were expressed in the condensing mesenchyme in normal human fetal kidneys, but were absent (SIX1) or reduced (SALL2) in cells at other developmental stages. These data imply that the blastema in WTs has progressed to the committed stage in the mesenchymal-epithelial transition, where it is partially arrested in differentiation. The WT-signature set also contained the Wnt receptor FZD7, the tumor antigen PRAME, the imprinted gene NNAT and the metastasis-associated transcription factor E1AF.

Kuerbitz SJ, Pahys J, Wilson A, et al.
Hypermethylation of the imprinted NNAT locus occurs frequently in pediatric acute leukemia.
Carcinogenesis. 2002; 23(4):559-64 [PubMed] Related Publications
Recent studies have demonstrated imprinting of the human neuronatin (NNAT) gene. NNAT maps to 20q11.2-q12, a region exhibiting loss of heterozygosity in acute myeloid leukemia and myelodysplastic/myeloproliferative disease. To investigate possible epigenetic dysregulation of genes in this region relevant to leukemogenesis, we analyzed methylation of the NNAT gene in normal tissues and in leukemias. We found a differential methylation pattern, typical of imprinted genes, at sites in the CpG island containing NNAT exon 1 in normal pituitary, peripheral blood cells and bone marrow-derived CD34-positive hematopoietic progenitor cells. Substantial or complete loss of the unmethylated NNAT allele was observed in leukemia cell lines and in 20 of 29 (69%) acute myeloid or lymphoid leukemia samples. While most highly expressed in brain, NNAT mRNA was also detected in normal hematopoietic progenitor cells and in leukemia cells exhibiting the normal methylation pattern, although not in hypermethylated leukemia cells. Demethylation by treatment of hypermethylated leukemia cells with 5-aza-2'-deoxycytidine resulted in reactivation of NNAT expression, concomitant with a reversion to the normal methylation pattern. The data demonstrate that hypermethylation of the NNAT locus is a frequent event in both myeloid and lymphoid acute leukemias of childhood. Aberrant hypermethylation of the NNAT locus suggests that the dysregulation of genes at 20q11.2-q12 in leukemia may be the result of epigenetic as well as genetic events.

Evans HK, Wylie AA, Murphy SK, Jirtle RL
The neuronatin gene resides in a "micro-imprinted" domain on human chromosome 20q11.2.
Genomics. 2001; 77(1-2):99-104 [PubMed] Related Publications
A small fraction of the genome contains genes that are imprinted and thus expressed exclusively from one parental allele. We report here that the human neuronatin gene (NNAT) on chromosome 20q11.2 is imprinted and transcribed specifically from the paternal allele. The region containing NNAT has multiple CpG islands, and methylation analysis showed that a 1.8-kb CpG island in its promoter region exhibits differential methylation in all tissues examined. This finding is consistent with the island acting as a component of the NNAT imprint control domain. NNAT lies within the singular 8.5-kb intron of the gene encoding bladder cancer-associated protein (BLCAP), which, as we demonstrate, is not imprinted. This study provides the first example, to our knowledge, in humans of an imprinted gene contained within the genomic structure of a nonimprinted gene. Thus, NNAT is in an imprinted "microdomain," making this locus uniquely suited for the investigation of mechanisms of localized imprint regulation.

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