Gene Summary

Gene:PKHD1; PKHD1, fibrocystin/polyductin
Summary:The protein encoded by this gene is predicted to have a single transmembrane (TM)-spanning domain and multiple copies of an immunoglobulin-like plexin-transcription-factor domain. Alternative splicing results in two transcript variants encoding different isoforms. Other alternatively spliced transcripts have been described, but the full length sequences have not been determined. Several of these transcripts are predicted to encode truncated products which lack the TM and may be secreted. Mutations in this gene cause autosomal recessive polycystic kidney disease, also known as polycystic kidney and hepatic disease-1. [provided by RefSeq, Jul 2008]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Source:NCBIAccessed: 16 March, 2017


What does this gene/protein do?
Show (15)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 16 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Disease Models, Animal
  • Newborns
  • Pedigree
  • Differential Diagnosis
  • Infant
  • Polycystic Kidney, Autosomal Recessive
  • Genetic Markers
  • Ultrasonography
  • Loss of Heterozygosity
  • Renal Cell Carcinoma
  • Liver Diseases
  • cdc25 Phosphatases
  • Signal Transduction
  • Childhood Cancer
  • Phenotype
  • Membrane Proteins
  • Cell Proliferation
  • Glucosidases
  • Kidney
  • Tamoxifen
  • Genes, Recessive
  • Adolescents
  • Liver
  • Chromosome 6
  • Cysts
  • TRPP Cation Channels
  • Transcription Factors
  • Polycystic Kidney, Autosomal Dominant
  • Receptor, erbB-2
  • Mutation
  • Choledochal Cyst
  • Heterozygote
  • Kidney Diseases, Cystic
  • Kidney Cancer
  • Genetic Predisposition
  • Tuberous Sclerosis
  • Multiple Abnormalities
  • Polycystic Kidney Diseases
  • Knockout Mice
  • Intracellular Signaling Peptides and Proteins
  • Sequence Homology
Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (1)

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: PKHD1 (cancer-related)

Catts ZA, Baig MK, Milewski B, et al.
Statewide Retrospective Review of Familial Pancreatic Cancer in Delaware, and Frequency of Genetic Mutations in Pancreatic Cancer Kindreds.
Ann Surg Oncol. 2016; 23(5):1729-35 [PubMed] Related Publications
BACKGROUND: Considering the typical rapid progression and high mortality of pancreatic cancer (PC), early detection may lead to an improved outcome. To date, there is no safe, sensitive, and cost-effective screening strategy to detect PC. Currently, screening is focused on individuals at the highest risk of developing PC based on family history. A high-risk individual is defined as having two or more first-degree relatives with PC, or one first- or second-degree relative with PC with a confirmed mutation in a gene associated with PC. The BRCA2 gene is one of the most common genes linked to pancreatic-only cancer families; however, other hereditary cancer syndromes have also been associated with an increased risk for PC.
METHODS: We conducted a retrospective review of pedigrees of families with a pancreatic adenocarcinoma cancer diagnosis held in the statewide Ruth Ann Minner High Risk Family Cancer Registry at the Helen F. Graham Cancer Center and Research Institute, Christiana Care Health System, Newark, DE, USA, from 2002 to 2013. The registry was queried based on how many first-, second-, or third-degree relatives of the proband were affected with PC, genetic testing status, and (if applicable) the results. These data were then categorized into families that meet familial PC (FPC) criteria, defined as two first-degree relatives with PC (FPC families), families that did not meet the FPC definition but had one first-degree relative affected with PC (first-degree families), and probands with PC (probands). Each family was counted only once in the analysis, even if multiple family members were tested.
RESULTS: Our analysis revealed that 175 of 597 families fitting any of the above criteria completed genetic testing. Of this cohort, 52 had pathogenic alterations with nine different genes implicated. Overall, 164 of the 175 families that fitted into any of the three categories previously identified had BRCA1 or BRCA2 testing, either by DNA sequencing or next-generation sequencing via a panel test that included BRCA1/2. BRCA1 pathogenic alterations were noted in 17/164 (10.4 %) and BRCA2 pathogenic alterations were noted in 23/164 (14.0 %). FPC families (n = 46) 42/46 of the FPC families underwent BRCA1/2 testing, and 11/42 (26 % [95 % CI 12.89-39.49]) had pathogenic alterations. Specifically, 4/42 = BRCA1 (9.5 %) and 7/42 = BRCA2 (16.7 %). Additionally, 16/46 of the FPC families underwent exclusively Lynch syndrome (LS) testing, and pathogenic mutations in a mismatch repair protein were identified in 2/16. Specifically, 1/16 = MLH1 (6.3 %) and 1/16 = MSH2 (3.6 %). Overall, a genetic mutation within any gene associated with an increased PC risk was found in 28 % of FPC families. First-degree families (n = 106) 99/106 of the families with one first-degree relative underwent BRCA1/2 testing, and 21/99 (21.2 % [95 % CI 13.16-29.27]) had pathogenic alterations. Specifically, 11/99 = BRCA1 (11.1 %) and 10/99 = BRCA2 (10.1 %). 32/99 first-degree families underwent exclusively LS testing, and pathogenic mutations were identified in 4/32. Specifically, 3/32 = MLH1 (9 %) and 1/32 = MSH6 (3 %). 25/99 of the families pursued panel testing, and pathogenic alterations in any gene were identified in 3/25. Specifically, the mutations were found in 1/25 = ATM (4 %), 1/25 = CHEK2 (4 %), and 1/25 = RAD51D (4 %). Affected probands (n = 23) Lastly, all 23 probands affected with PC pursued genetic testing. Of these, 11/23 were found to have pathogenic alterations. All 23 underwent BRCA1/2 testing, and pathogenic alterations were identified in 8/23 (35 % [95 % CI 15.32-54.25]), specifically 2/23 = BRCA1 (9 %), and 6/23 = BRCA2 (26 %). 10/23 patients underwent panel testing and pathogenic alterations were found in 3/10 (30 %) patients, of whom 1/10 = MSH6 (10 %), 1/10 = ATM (10 %), and 1/10 = TP53 (10 %).
CONCLUSIONS: This study demonstrates that a statewide high-risk family cancer registry is an important instrument in studying the risk of PC in families. Our analysis revealed 14 mutations associated with FPC, among which hereditary breast and ovarian cancer and LS were most prevalent. BRCA1 was found to have the same association with PC as BRCA2, which appears unique to our population. We plan to use our knowledge of these mutations in developing a PC screening program.

Hou Q, Chen K, Shan Z
The construction of cDNA library and the screening of related antigen of ascitic tumor cells of ovarian cancer.
Eur J Gynaecol Oncol. 2015; 36(5):590-4 [PubMed] Related Publications
OBJECTIVE: To construct the cDNA library of the ascites tumor cells of ovarian cancer, which can be used to screen the related antigen for the early diagnosis of ovarian cancer and therapeutic targets of immune treatment.
MATERIALS AND METHODS: Four cases of ovarian serous cystadenocarcinoma, two cases of ovarian mucinous cystadenocarcinoma, and two cases of ovarian endometrial carcinoma in patients with ascitic tumor cells which were used to construct the cDNA library. To screen the ovarian cancer antigen gene, evaluate the enzyme, and analyze nucleotide sequence, serological analysis of recombinant tumor cDNA expression libraries (SEREX) and suppression subtractive hybridization technique (SSH) techniques were utilized. The detection method of recombinant expression-based serological mini-arrays (SMARTA) was used to detect the ovarian cancer antigen and the positive reaction of 105 cases of ovarian cancer patients and 105 normal women's autoantibodies correspondingly in serum.
RESULTS: After two rounds of serologic screening and glycosides sequencing analysis, 59 candidates of ovarian cancer antigen gene fragments were finally identified, which corresponded to 50 genes. They were then divided into six categories: (1) the homologous genes which related to the known ovarian cancer genes, such as BARD 1 gene, etc; (2) the homologous genes which were associated with other tumors, such as TM4SFI gene, etc; (3) the genes which were expressed in a special organization, such as ILF3, FXR1 gene, etc; (4) the genes which were the same with some protein genes of special function, such as TIZ, ClD gene; (5) the homologous genes which possessed the same source with embryonic genes, such as PKHD1 gene, etc; (6) the remaining genes were the unknown genes without the homologous sequence in the gene pool, such as OV-189 genes.
CONCLUSION: SEREX technology combined with SSH method is an effective research strategy which can filter tumor antigen with high specific character; the corresponding autoantibodies of TM4SFl, ClD, TIZ, BARDI, FXRI, and OV-189 gene's recombinant antigen in serum can be regarded as the biomarkers which are used to diagnose ovarian cancer. The combination of multiple antigen detection can improve diagnostic efficiency.

Petersen GM
Familial Pancreatic Adenocarcinoma.
Hematol Oncol Clin North Am. 2015; 29(4):641-53 [PubMed] Free Access to Full Article Related Publications
Familial pancreatic cancer (FPC) kindreds have at least 2 first-degree relatives with pancreatic ductal adenocarcinoma. Studies of FPC have focused on the discovery of genetic cause and on the management of those at genetically high risk. Research reveals that a half dozen known hereditary syndromes or genes are associated with increased risk of developing pancreatic cancer, the most prominent of which are BRCA2 and CDKN2A. Genetic risk assessment and testing is already available. Owing to limited experience worldwide, guidance is often based on expert opinion, although all agree that research is needed to improve the shaping of options.

Mocci E, Guillen-Ponce C, Earl J, et al.
PanGen-Fam: Spanish registry of hereditary pancreatic cancer.
Eur J Cancer. 2015; 51(14):1911-7 [PubMed] Related Publications
PURPOSE: To describe the organisation of the registry and the preliminary results in terms of characteristics of high-risk pancreatic ductal adenocarcinoma (PDAC) families recruited to date and findings of the screening programme. To compare early onset sporadic cases (⩽50 years), sporadic cases (>50 years) and cases with family history of cancer, for PDAC possible risk factors.
METHODS/PATIENTS: Families with hereditary cancer syndromes predisposing to PDAC were recruited from two main sources: Spanish hospitals participating in PanGenEU, a pan-European multicentre case-control study, and their genetic counseling unit. Individuals at high-risk of PDAC were enrolled into a screening programme, consisting of Endoscopic ultrasound, computerised tomography, magnetic resonance imaging. Genetic testing of candidate genes was offered according to each patient's risk.
RESULTS: Among 577 consecutive PDAC cases, recruited via PanGenEU, 36 (6%) had ⩾2 first-degree relative with PDAC: Familial pancreatic cancer (FPC). So far PanGen-Fam has recruited 42 high-risk PDAC families; 25 (60%) had FPC. Five index cases with cancer were positive for BRCA2 and one for BRCA1 germline mutations. In the second year of prospective PDAC screening, one neuroendocrine tumour and a high-grade dysplasia lesion suspicious of carcinoma were diagnosed among 41 high-risk individuals. Furthermore EUS detected chronic-pancreatitis-like parenchymal changes in 15 patients.
CONCLUDING STATEMENT: The identification and recruitment of PDAC high-risk families into the PanGen-Fam registry provides an opportunity to detect early onset cancer and precursor pancreatic cancer lesions at a potentially curative stage and to increase the knowledge of the natural history of the disease.

Cramer MT, Guay-Woodford LM
Cystic kidney disease: a primer.
Adv Chronic Kidney Dis. 2015; 22(4):297-305 [PubMed] Related Publications
Renal cystic diseases encompass a broad group of disorders with variable phenotypic expression. Cystic disorders can present during infancy, childhood, or adulthood. Often, but not always, they can be distinguished by the clinical features including age at presentation, renal imaging characteristics, including cyst distribution, and the presence/distribution of extrarenal manifestations. It is important to take the clinical context into consideration when assessing renal cystic disease in children and adults. For example, solitary kidney cysts may be completely benign when they develop during adulthood but may represent early polycystic kidney disease when observed during childhood. In this review, we have categorized renal cystic disease according to inherited single-gene disorders, for example, autosomal recessive polycystic kidney disease; syndromic disorders associated with kidney cysts, for example, tuberous sclerosis complex; and nongenetic forms of renal cystic disease, for example, simple kidney cysts. We present an overview of the clinical characteristics, genetics (when appropriate), and molecular pathogenesis and the diagnostic evaluation and management of each renal cystic disease. We also provide an algorithm that distinguishes kidney cysts based on their clinical features and may serve as a helpful diagnostic tool for practitioners. A review of Autosomal Dominant Polycystic Disease was excluded as this disorder was reviewed in this journal in March 2010, volume 17, issue 2.

Tao S, Kakade VR, Woodgett JR, et al.
Glycogen synthase kinase-3β promotes cyst expansion in polycystic kidney disease.
Kidney Int. 2015; 87(6):1164-75 [PubMed] Free Access to Full Article Related Publications
Polycystic kidney diseases (PKDs) are inherited disorders characterized by the formation of fluid filled renal cysts. Elevated cAMP levels in PKDs stimulate progressive cyst enlargement involving cell proliferation and transepithelial fluid secretion often leading to end-stage renal disease. The glycogen synthase kinase-3 (GSK3) family of protein kinases consists of GSK3α and GSK3β isoforms and has a crucial role in multiple cellular signaling pathways. We previously found that GSK3β, a regulator of cell proliferation, is also crucial for cAMP generation and vasopressin-mediated urine concentration by the kidneys. However, the role of GSK3β in the pathogenesis of PKDs is not known. Here we found that GSK3β expression and activity were markedly upregulated and associated with cyst-lining epithelia in the kidneys of mice and humans with PKD. Renal collecting duct-specific gene knockout of GSK3β or pharmacological inhibition of GSK3 effectively slowed down the progression of PKD in mouse models of autosomal recessive or autosomal dominant PKD. GSK3 inactivation inhibited cAMP generation and cell proliferation resulting in reduced cyst expansion, improved renal function, and extended life span. GSK3β inhibition also reduced pERK, c-Myc, and cyclin-D1, known mitogens in proliferation of cystic epithelial cells. Thus, GSK3β has a novel functional role in PKD pathophysiology, and its inhibition may be therapeutically useful to slow down cyst expansion and progression of PKD.

Humphris JL, Johns AL, Simpson SH, et al.
Clinical and pathologic features of familial pancreatic cancer.
Cancer. 2014; 120(23):3669-75 [PubMed] Related Publications
BACKGROUND: Inherited predisposition to pancreatic cancer contributes significantly to its incidence and presents an opportunity for the development of early detection strategies. The genetic basis of predisposition remains unexplained in a high proportion of patients with familial PC (FPC).
METHODS: Clinicopathologic features were assessed in a cohort of 766 patients who had been diagnosed with pancreatic ductal adenocarcinoma (PC). Patients were classified with FPC if they had ≥1 affected first-degree relatives; otherwise, they were classified with sporadic PC (SPC).
RESULTS: The prevalence of FPC in this cohort was 8.9%. In FPC families with an affected parent-child pair, 71% in the subsequent generation were 12.3 years younger at diagnosis. Patients with FPC had more first-degree relatives who had an extrapancreatic malignancy (EPM) (42.6% vs 21.2; P<.0001), particularly melanoma and endometrial cancer, but not a personal history of EPM. Patients with SPC were more likely to be active smokers, have higher cumulative tobacco exposure, and have fewer multifocal precursor lesions, but these were not associated with differences in survival. Long-standing diabetes mellitus (>2 years) was associated with poor survival in both groups.
CONCLUSIONS: FPC represents 9% of PC, and the risk of malignancy in kindred does not appear to be confined to the pancreas. Patients with FPC have more precursor lesions and include fewer active smokers, but other clinicopathologic factors and outcome are similar to those in patients with SPC. Furthermore, some FPC kindreds may exhibit anticipation. A better understanding of the clinical features of PC will facilitate efforts to uncover novel susceptibility genes and the development of early detection strategies.

Norris AL, Roberts NJ, Jones S, et al.
Familial and sporadic pancreatic cancer share the same molecular pathogenesis.
Fam Cancer. 2015; 14(1):95-103 [PubMed] Free Access to Full Article Related Publications
Pancreatic ductal adenocarcinoma (PDAC) is nearly uniformly lethal, with a median overall survival in 2014 of only 6 months. The genetic progression of sporadic PDAC (SPC) is well established, with common somatic alterations in KRAS, p16/CDKN2A, TP53, and SMAD4/DPC4. Up to 10 % of all PDAC cases occur in families with two or more affected first-degree relatives (familial pancreatic cancer, FPC), but these cases do not appear to present at an obviously earlier age of onset. This is unusual because most familial cancer syndrome patients present at a substantially younger age than that of corresponding sporadic cases. Here we collated the reported age of onset for FPC and SPC from the literature. We then used an integrated approach including whole exomic sequencing, whole genome sequencing, RNA sequencing, and high density SNP microarrays to study a cohort of FPC cell lines and corresponding germline samples. We show that the four major SPC driver genes are also consistently altered in FPC and that each of the four detection strategies was able to detect the mutations in these genes, with one exception. We conclude that FPC undergoes a similar somatic molecular pathogenesis as SPC, and that the same gene targets can be used for early detection and minimal residual disease testing in FPC patients.

Ghiorzo P
Genetic predisposition to pancreatic cancer.
World J Gastroenterol. 2014; 20(31):10778-89 [PubMed] Free Access to Full Article Related Publications
Pancreatic adenocarcinoma (PC) is the most deadly of the common cancers. Owing to its rapid progression and almost certain fatal outcome, identifying individuals at risk and detecting early lesions are crucial to improve outcome. Genetic risk factors are believed to play a major role. Approximately 10% of PC is estimated to have familial inheritance. Several germline mutations have been found to be involved in hereditary forms of PC, including both familial PC (FPC) and PC as one of the manifestations of a hereditary cancer syndrome or other hereditary conditions. Although most of the susceptibility genes for FPC have yet to be identified, next-generation sequencing studies are likely to provide important insights. The risk of PC in FPC is sufficiently high to recommend screening of high-risk individuals; thus, defining such individuals appropriately is the key. Candidate genes have been described and patients considered for screening programs under research protocols should first be tested for presence of germline mutations in the BRCA2, PALB2 and ATM genes. In specific PC populations, including in Italy, hereditary cancer predisposition genes such as CDKN2A also explain a considerable fraction of FPC.

Mastoraki A, Chatzimavridou-Grigoriadou V, Chatzipetrou V, et al.
Familial pancreatic cancer: challenging diagnostic approach and therapeutic management.
J Gastrointest Cancer. 2014; 45(3):256-61 [PubMed] Related Publications
BACKGROUND: Familial predisposition characterizes up to 10% of the patients with pancreatic cancer (PC). Although many syndromes have been associated with an increased risk for PC, familial pancreatic cancer (FPC) accounts for the majority of hereditary cases. FPC is defined by families with at least a pair of first-degree relatives (FDRs) who have been diagnosed with PC and do not fulfill the criteria of other inherited tumor syndromes.
METHODS AND RESULTS: Genetic counseling is of great importance to estimate the prevalence and recommend further molecular testing. Regarding the screening program for individuals with increased risk for PC, a consortium summit stated that candidates for screening are FDRs of patients with PC from a familial kindred with at least two affected FDRs, patients with Peutz-Jeghers syndrome and p16, BRCA2, and hereditary nonpolyposis colorectal cancer (HNPCC) mutation carriers. It was also agreed that initial screening should include endoscopic ultrasonography (EUS) and/or magnetic resonance imaging (MRI)/magnetic resonance cholangiopancreatography (MRCP) instead of computed tomography (CT) or endoscopic retrograde cholangiopancreatography (ERCP).
CONCLUSIONS: However, the optimal age of initial screening remains undefined. Furthermore, a multidisciplinary assessment is required to determine whether surgical interventions should be performed at high-volume specialty centers. The aim of this study is to collect all the recent information considering the genetic basis, screening protocols, and treatment of FPC in order to provide an update on the current contemporary concepts of therapeutic management of the disease.

Huhn S, Bevier M, Pardini B, et al.
Colorectal cancer risk and patients' survival: influence of polymorphisms in genes somatically mutated in colorectal tumors.
Cancer Causes Control. 2014; 25(6):759-69 [PubMed] Related Publications
PURPOSE: The first two studies aiming for the high-throughput identification of the somatic mutation spectrum of colorectal cancer (CRC) tumors were published in 2006 and 2007. Using exome sequencing, they described 69 and 140 candidate cancer genes (CAN genes), respectively. We hypothesized that germline variants in these genes may influence CRC risk, similar to APC, which is causing CRC through germline and somatic mutations.
METHODS: After excluding the well-established CRC genes APC, KRAS, TP53, and ABCA1, we analyzed 35 potentially functional single-nucleotide polymorphisms (SNPs) in 10 CAN genes (OBSCN, MLL3, PKHD1, SYNE1, ERCC6, FBXW7, EPHB6/TRPV6, ELAC1/SMAD4, EPHA3, and ADAMTSL3) using KBiosciences Competitive Allele-Specific PCR™ genotyping assays. In addition to CRC risk (1,399 CRC cases, 838 controls), we also considered the influence of the SNPs on patients' survival (406 cases).
RESULTS: In spite of the fact that our in silico analyses suggested functional relevance for the studied genes and SNPs, our data did not support a strong influence of the studied germline variants on CRC risk and survival. The strongest association with CRC risk and survival was found for MLL3 (rs6464211, OR 1.50, p = 0.002, dominant model; HR 2.12, p = 0.020, recessive model). Two SNPs in EPHB6/TRPV6 (dominant model) showed marginal associations with survival (rs4987622 HR 0.58 p = 0.028 and rs6947538 HR 0.64, p = 0.036, respectively).
CONCLUSION: Although somatic mutations in the CAN genes have been related to the development and progression of various types of cancers in several next-generation sequencing or expression analyses, our study suggests that the studied potentially functional germline variants are not likely to affect CRC risk or survival.

Fedeles SV, Gallagher AR, Somlo S
Polycystin-1: a master regulator of intersecting cystic pathways.
Trends Mol Med. 2014; 20(5):251-60 [PubMed] Free Access to Full Article Related Publications
Autosomal dominant polycystic kidney disease (ADPKD) is the most common potentially lethal monogenic disorder, with more than 12 million cases worldwide. The two causative genes for ADPKD, PKD1 and PKD2, encode protein products polycystin-1 (PC1) and polycystin-2 (PC2 or TRPP2), respectively. Recent data have shed light on the role of PC1 in regulating the severity of the cystic phenotypes in ADPKD, autosomal recessive polycystic kidney disease (ARPKD), and isolated autosomal dominant polycystic liver disease (ADPLD). These studies showed that the rate for cyst growth was a regulated trait, a process that can be either sped up or slowed down by alterations in functional PC1. These findings redefine the previous understanding that cyst formation occurs as an 'on-off' process. Here, we review these and other related studies with an emphasis on their translational implications for polycystic diseases.

Al-Lawati TT
Fibropolycystic disease of the liver and kidney in Oman.
Arab J Gastroenterol. 2013; 14(4):173-5 [PubMed] Related Publications
BACKGROUND AND STUDY AIMS: Fibropolycystic disease of liver and kidney (FPCDLK) is an uncommon group of conditions inherited in an autosomal fashion. The group encompasses autosomal dominant polycystic disease of the kidney (ADPDK), autosomal recessive polycystic disease of the kidney (ARPDK), congenital hepatic fibrosis (CHF) and Caroli's disease (CD). There are limited data of this disease in the world. We report our experience in the Royal Hospital (RH) in Oman and data regarding long-term follow-up. The aim of the study was to document the frequency of encounter, clinical presentation and outcome of FPCDLK in Division of Child Health in RH, Muscat.
PATIENTS AND METHODS: Charts of patients diagnosed with ARPDK, ADPDK, CHF and CD were reviewed from the period of 16 February 2006 till 31 December 2011. Parameters including anthropometry, liver function tests, renal function tests, presence of oesophageal varices, hypersplenism, renal or liver transplantation and performance of porto-systemic shunt surgeries were all investigated.
RESULTS: A total of 33 patients were identified, including 19 males and 14 females. The frequency of encounter of FPCDLK in RH was 1.5/1,000,000 population. The mean age of patients was 7.4years. The mean age at diagnosis was 27months. The mean duration of follow-up was 5.5years. A total of 31% of patients had an incidental finding of hepatomegaly, and 25% were detected by antenatal screening. Three children presented with renal failure, and 13 children in total had renal function abnormalities by the end of the study period. One child presented with haematemesis at the age of 1year. Two children underwent renal transplant and one child required splenectomy with a splenorenal shunt. A total of 54% had endoscopic variceal screen and two required banding on first endoscopy. The demise of one patient was observed during the study.
CONCLUSION: FPCDLK is uncommon in Oman but carries major mortality and morbidity for the patient and family. The gene is present in the Gulf countries. Management is mainly through portal hypertension and renal supportive care until definitive dual organ transplant. This disease needs to be further investigated in the Arab world.

Chung EM, Conran RM, Schroeder JW, et al.
From the radiologic pathology archives: pediatric polycystic kidney disease and other ciliopathies: radiologic-pathologic correlation.
Radiographics. 2014 Jan-Feb; 34(1):155-78 [PubMed] Related Publications
Genetic defects of cilia cause a wide range of diseases, collectively known as ciliopathies. Primary, or nonmotile, cilia function as sensory organelles involved in the regulation of cell growth, differentiation, and homeostasis. Cilia are present in nearly every cell in the body and mutations of genes encoding ciliary proteins affect multiple organs, including the kidneys, liver, pancreas, retina, central nervous system (CNS), and skeletal system. Genetic mutations causing ciliary dysfunction result in a large number of heterogeneous phenotypes that can manifest with a variety of overlapping abnormalities in multiple organ systems. Renal manifestations of ciliopathies are the most common abnormalities and include collecting duct dilatation and cyst formation in autosomal recessive polycystic kidney disease (ARPKD), cyst formation anywhere in the nephron in autosomal dominant polycystic kidney disease (ADPKD), and tubulointerstitial fibrosis in nephronophthisis, as well as in several CNS and skeletal malformation syndromes. Hepatic disease is another common manifestation of ciliopathies, ranging from duct dilatation and cyst formation in ARPKD and ADPKD to periportal fibrosis in ARPKD and several malformation syndromes. The unifying molecular pathogenesis of this emerging class of disorders explains the overlap of abnormalities in disparate organ systems and links diseases of widely varied clinical features. It is important for radiologists to be able to recognize the multisystem manifestations of these syndromes, as imaging plays an important role in diagnosis and follow-up of affected patients.

Deng L, Zhang Y, Ma L, et al.
Comparison of anti-EGFR-Fab' conjugated immunoliposomes modified with two different conjugation linkers for siRNa delivery in SMMC-7721 cells.
Int J Nanomedicine. 2013; 8:3271-83 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Targeted liposome-polycation-DNA complex (LPD), mainly conjugated with antibodies using functionalized PEG derivatives, is an effective nanovector for systemic delivery of small interference RNA (siRNA). However, there are few studies reporting the effect of different conjugation linkers on LPD for gene silencing. To clarify the influence of antibody conjugation linkers on LPD, we prepared two different immunoliposomes to deliver siRNA in which DSPE-PEG-COOH and DSPE-PEG-MAL, the commonly used PEG derivative linkers, were used to conjugate anti-EGFR Fab' with the liposome.
METHODS: First, 600 μg of anti-EGFR Fab' was conjugated with 28.35 μL of a micelle solution containing DSPE-PEG-MAL or DSPE-PEG-COOH, and then post inserted into the prepared LPD. Various liposome parameters, including particle size, zeta potential, stability, and encapsulation efficiency were evaluated, and the targeting ability and gene silencing activity of TLPD-FPC (DSPE-PEG-COOH conjugated with Fab') was compared with that of TLPD-FPM (DSPE-PEG-MAL conjugated with Fab') in SMMC-7721 hepatocellular carcinoma cells.
RESULTS: There was no significant difference in particle size between the two TLPDs, but the zeta potential was significantly different. Further, although there was no significant difference in siRNA encapsulation efficiency, cell viability, or serum stability between TLPD-FPM and TLPD-FPC, cellular uptake of TLPD-FPM was significantly greater than that of TLPD-FPC in EGFR-overexpressing SMMC-7721 cells. The luciferase gene silencing efficiency of TLPD-FPM was approximately three-fold high than that of TLPD-FPC.
CONCLUSION: Different conjugation linkers whereby antibodies are conjugated with LPD can affect the physicochemical properties of LPD and antibody conjugation efficiency, thus directly affecting the gene silencing effect of TLPD. Immunoliposomes prepared by DSPE-PEG-MAL conjugation with anti-EGFR Fab' are more effective than TLPD containing DSPE-PEG-COOH in targeting hepatocellular carcinoma cells for siRNA delivery.

Fendrich V, Langer P, Bartsch DK
Familial pancreatic cancer--status quo.
Int J Colorectal Dis. 2014; 29(2):139-45 [PubMed] Related Publications
INTRODUCTION: Familial pancreatic cancer (FPC) is defined by families with at least two first-degree relatives with confirmed pancreatic ductal adenocarcinoma (PDAC) that do not fulfill the criteria of other inherited tumor syndromes with an increased risk for the development of PDAC, such as hereditary pancreatitis or hereditary breast and ovarian cancer. FPC is mostly autosomal dominant inherited and presents with a heterogeneous phenotype. Although the major gene defect has not yet been identified, some important germline mutations in the BRCA2-, PALB2-, and ATM-genes are causative in some FPC families.
FPC SCREENING: It is suggested by experts to include high-risk individuals in a screening program with a multidisciplinary approach under research protocol conditions. However, neither biomarkers nor reliable imaging modalities for the detection of high-grade precursor lesions are yet available. Most screening programs are currently based on endoscopic ultrasound and magnetic resonance imaging, and first data demonstrated that precursor lesions (pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm) of PDAC can be identified. Timing and extent of surgery are still a matter of debate.
SCOPE OF THE REVIEW: The present review focuses on the clinical phenotype of FPC, its histopathological characteristics, known underlying genetic changes, genetic counseling, and screening.

Wada K, Takaori K, Traverso LW, et al.
Clinical importance of Familial Pancreatic Cancer Registry in Japan: a report from kick-off meeting at International Symposium on Pancreas Cancer 2012.
J Hepatobiliary Pancreat Sci. 2013; 20(6):557-66 [PubMed] Related Publications
Pancreatic cancer is still a highly lethal disease with a 5-year survival rate of approximately 5 %. Early detection offers one of the best hopes for improving survival. Previous cohort studies and case-control studies showed that 4-10 % of pancreatic cancers have a hereditary basis, and individuals with a family history have an increased risk of developing pancreatic and extra-pancreatic malignancies. Since individuals with a family history of pancreatic cancer and those with a known genetic syndrome that predisposes to pancreatic cancer will be the first to benefit from early detection tests as they become available, familial pancreatic cancer (FPC) registries have been established in the US and Europe, but not yet in Japan. Such registries form the basis for epidemiological studies, clinical trials, and basic research on familial pancreatic cancer. There is a need for FPC registries in Japan as cancer risk varies among different populations and discoveries made in Western populations may not translate to the Japanese population. These registries in Japan will align with ongoing international efforts and add to a better understanding of the natural history, risk factors, screening strategies, and responsible genes, for improving survival of this dismal disease.

Grant RC, Al-Sukhni W, Borgida AE, et al.
Exome sequencing identifies nonsegregating nonsense ATM and PALB2 variants in familial pancreatic cancer.
Hum Genomics. 2013; 7:11 [PubMed] Free Access to Full Article Related Publications
We sequenced 11 germline exomes from five families with familial pancreatic cancer (FPC). One proband had a germline nonsense variant in ATM with somatic loss of the variant allele. Another proband had a nonsense variant in PALB2 with somatic loss of the variant allele. Both variants were absent in a relative with FPC. These findings question the causal mechanisms of ATM and PALB2 in these families and highlight challenges in identifying the causes of familial cancer syndromes using exome sequencing.

Frank V, Habbig S, Bartram MP, et al.
Mutations in NEK8 link multiple organ dysplasia with altered Hippo signalling and increased c-MYC expression.
Hum Mol Genet. 2013; 22(11):2177-85 [PubMed] Related Publications
Mutations affecting the integrity and function of cilia have been identified in various genes over the last decade accounting for a group of diseases called ciliopathies. Ciliopathies display a broad spectrum of phenotypes ranging from mild manifestations to lethal combinations of multiple severe symptoms and most of them share cystic kidneys as a common feature. Our starting point was a consanguineous pedigree with three affected fetuses showing an early embryonic phenotype with enlarged cystic kidneys, liver and pancreas and developmental heart disease. By genome-wide linkage analysis, we mapped the disease locus to chromosome 17q11 and identified a homozygous nonsense mutation in NEK8/NPHP9 that encodes a kinase involved in ciliary dynamics and cell cycle progression. Missense mutations in NEK8/NPHP9 have been identified in juvenile cystic kidney jck mice and in patients suffering from nephronophthisis (NPH), an autosomal-recessive cystic kidney disease. This work confirmed a complete loss of NEK8 expression in the affected fetuses due to nonsense-mediated decay. In cultured fibroblasts derived from these fetuses, the expression of prominent polycystic kidney disease genes (PKD1 and PKD2) was decreased, whereas the oncogene c-MYC was upregulated, providing potential explanations for the observed renal phenotype. We furthermore linked NEK8 with NPHP3, another NPH protein known to cause a very similar phenotype in case of null mutations. Both proteins interact and activate the Hippo effector TAZ. Taken together, our study demonstrates that NEK8 is essential for organ development and that the complete loss of NEK8 perturbs multiple signalling pathways resulting in a severe early embryonic phenotype.

Banales JM, Munoz-Garrido P, Bujanda L
Somatic second-hit mutations leads to polycystic liver diseases.
World J Gastroenterol. 2013; 19(1):141-3 [PubMed] Free Access to Full Article Related Publications
Polycystic liver diseases (PCLDs) are a heterogeneous group of genetic disorders characterized by the development of multiple fluid-filled cysts in the liver, which derive from cholangiocytes, the epithelial cells lining the bile ducts. When these cysts grow, symptoms such as abdominal distension, nausea, and abdominal pain may occur. PCLDs may exist isolated (i.e., autosomal dominant polycystic liver disease, ADPLD) or in combination with renal cystogenesis (i.e., autosomal dominant polycystic kidney disease and autosomal recessive polycystic liver disease). The exact prevalence of PCLDs is unknown, but is estimated to occur in approximately 1:1000 persons. Although the pathogenesis of each form of PCLD appears to be different, increasing evidences indicate that hepatic cystogenesis is a phenomenon that may involve somatic loss of heterozygosity (LOH) in those pathological conditions inherited in a dominant form. A recent report, using highly sophisticated methodology, demonstrated that ADPLD patients with a germline mutation in the protein kinase C substrate 80K-H (PRKCSH) gene mostly develop hepatic cystogenesis through a second somatic mutation. While hepatocystin, the PRKCSH-encoding protein, was absent in the hepatic cysts with LOH, it was still expressed in the heterozygous cysts. On the other hand, no additional trans-heterozygous mutations on the SEC63 homolog (S. cerevisiae/SEC63) gene (also involved in the development of PCLDs) were observed. These data indicate that PCLD is recessive at the cellular level, and point out the important role of hepatocystin loss in cystogenesis. In this commentary, we discuss the knowledge regarding the role of somatic second-hit mutations in the development of PCLDs, and the most relevant findings have been highlighted.

Al-Sukhni W, Joe S, Lionel AC, et al.
Identification of germline genomic copy number variation in familial pancreatic cancer.
Hum Genet. 2012; 131(9):1481-94 [PubMed] Free Access to Full Article Related Publications
Adenocarcinoma of the pancreas is a significant cause of cancer mortality, and up to 10 % of cases appear to be familial. Heritable genomic copy number variants (CNVs) can modulate gene expression and predispose to disease. Here, we identify candidate predisposition genes for familial pancreatic cancer (FPC) by analyzing germline losses or gains present in one or more high-risk patients and absent in a large control group. A total of 120 FPC cases and 1,194 controls were genotyped on the Affymetrix 500K array, and 36 cases and 2,357 controls were genotyped on the Affymetrix 6.0 array. Detection of CNVs was performed by multiple computational algorithms and partially validated by quantitative PCR. We found no significant difference in the germline CNV profiles of cases and controls. A total of 93 non-redundant FPC-specific CNVs (53 losses and 40 gains) were identified in 50 cases, each CNV present in a single individual. FPC-specific CNVs overlapped the coding region of 88 RefSeq genes. Several of these genes have been reported to be differentially expressed and/or affected by copy number alterations in pancreatic adenocarcinoma. Further investigation in high-risk subjects may elucidate the role of one or more of these genes in genetic predisposition to pancreatic cancer.

Bartsch DK, Gress TM, Langer P
Familial pancreatic cancer--current knowledge.
Nat Rev Gastroenterol Hepatol. 2012; 9(8):445-53 [PubMed] Related Publications
Familial pancreatic cancer (FPC) describes families with at least two first-degree relatives with confirmed exocrine pancreatic cancer that do not fulfil the criteria of other inherited tumour syndromes with increased risks of pancreatic cancer, such as Peutz-Jeghers syndrome, hereditary pancreatitis, and hereditary breast and ovarian cancer. The inheritance of FPC is mostly autosomal dominant and with a heterogeneous phenotype. The major gene defect is yet to be identified, although germline mutations in BRCA2, PALB2 and ATM are causative in some FPC families. Expert consensus conferences considered it appropriate to screen for pancreatic cancer in high-risk individuals using a multidisciplinary approach under research protocol conditions. However, neither biomarkers nor reliable imaging modalities for the detection of high-grade precursor lesions are yet available. Most screening programmes are currently based on findings from endoscopic ultrasonography and MRI, and data has demonstrated that precursor lesions of pancreatic cancer can be identified. No consensus exists regarding the age to initiate or stop screening and the optimal intervals for follow-up. Timing and extent of surgery as a treatment for FPC are debated. This Review focuses on the clinical phenotype of FPC, its histopathological characteristics, known underlying genetic changes and associated genetic counselling and screening.

Zingg-Schenk A, Caduff J, Azzarello-Burri S, et al.
Boy with autosomal recessive polycystic kidney and autosomal dominant polycystic liver disease.
Pediatr Nephrol. 2012; 27(7):1197-200 [PubMed] Related Publications
BACKGROUND: Autosomal recessive polycystic kidney disease (ARPKD) shows a great phenotypic variability between patients, ranging from perinatal demise to mildly affected adults. Autosomal dominant polycystic liver disease (PCLD) does not manifest in childhood.
CASE-DIAGNOSIS/TREATMENT: A boy was reported with the co-occurrence of ARPKD and PCLD. He presented at the age of 16 days with pyelonephritis and urosepsis. Subsequent investigations showed enlarged kidneys and hyperechogenic renal medulla and liver parenchyma. Genetic analysis revealed compound heterozygous mutations in the PKHD1 gene (p.Arg496X and p.Ser1862Leu). After his mother was diagnosed with PCLD, the finding of a liver cyst on ultrasound prompted analysis of the PRKCSH gene, revealing a missense mutation (p.Arg139His). At the most recent follow-up at 13 years of age, the patient's course and clinical examination was uneventful with normal renal and liver function without evidence of portal hypertension.
CONCLUSIONS: The patient with ARPKD and PCLD has so far demonstrated a benign clinical outcome, consistent with the great phenotypic variability of ARPKD and, apart from the liver cyst, asymptomatic manifestation of PCLD in childhood. However, close long-term follow-up is mandatory.

Ghiorzo P, Fornarini G, Sciallero S, et al.
CDKN2A is the main susceptibility gene in Italian pancreatic cancer families.
J Med Genet. 2012; 49(3):164-70 [PubMed] Related Publications
Background Most familial pancreatic cancer (FPC) remains unexplained. The identification of individuals with a high genetic risk of developing pancreatic adenocarcinoma (PC) is important to elucidate its biological basis and is critical to better define emerging strategies for the detection of early pancreatic neoplasms. Patients and methods A series of 225 consecutively enrolled patients with PC were tested for CDKN2A mutations. After personal and family cancer histories of all the patients had been reviewed, a subset of the patients were classified as FPC and were also tested for mutations in PALLD, PALB2, BRCA1 and BRCA2 as FPC candidate genes. Results The CDKN2A mutation rate in the 225 PC cases was 5.7%. The CDKN2A founder mutations, p.E27X and p.G101W, were predominant, but the mutation spectrum also included p.L65P, p.G67R and two novel, potentially pathogenic variants, promoter variant c.-201ACTC>CTTT and p.R144C. None of the patients with FPC harboured germline mutations in PALLD, PALB2 or BRCA2. One family was positive for the BRCA1 UV variant p.P727L. Strikingly, five of 16 patients with FPC (31%) carried CDKN2A mutations. Conclusion These findings suggest that a sizeable subset of Italian FPC families may carry CDKN2A mutations. This result may be of value for identifying the best candidates for future PC screening trials in Italy.

Oyazato Y, Iijima K, Emi M, et al.
Molecular analysis of TSC2/PKD1 contiguous gene deletion syndrome.
Kobe J Med Sci. 2011; 57(1):E1-10 [PubMed] Related Publications
BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by mutations in either of two genes, TSC1 and TSC2. Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in either PKD1 or PKD2. TSC2 lies immediately adjacent to PKD1 and large heterozygous deletions can result in the TSC2/PKD1 contiguous gene syndrome (PKDTS). PKDTS has been identified in patients with TSC and early-onset severe ADPKD. However, genetic diagnosis with conventional methods proved to be difficult because its genetic aberrations are large monoallelic mutations.
METHODS: In the study presented here, we used both multiplex ligation-dependent probe amplification (MLPA) and array comparative genomic hybridization (array-CGH) for four PKDTS patients.
RESULTS: We were able to detect large heterozygous deletions including TSC2 and PKD1 by both of MLPA and array-CGH in all four patients. And in two patients, array-CGH identified relatively large genomic aberrations (RAB26, NTHL1, etc.), that extended outside of TSC2 or PKD1.
CONCLUSION: The identical results obtained with these two completely different methods show that both constitute highly reliable strategies. Only a few studies have determined the breakpoints of large deletions in this disease and ours is the first to have identified the breakpoints by using array-CGH. We suggest that these methods are not only useful for the diagnosis of PKDTS but also for elucidation of its molecular mechanism.

Harinck F, Kluijt I, van Mil SE, et al.
Routine testing for PALB2 mutations in familial pancreatic cancer families and breast cancer families with pancreatic cancer is not indicated.
Eur J Hum Genet. 2012; 20(5):577-9 [PubMed] Free Access to Full Article Related Publications
PALB2-mutation carriers not only have an increased risk for breast cancer (BC) but also for pancreatic cancer (PC). Thus far, PALB2 mutations have been mainly found in PC patients from families affected by both PC and BC. As it is well known that the prevalence of gene mutations varies between different populations, we studied the prevalence of PALB2 mutations in a Dutch cohort of non-BRCA1/2 familial PC (FPC) families and in non-BRCA1/2 familial BC (FBC) families with at least one PC case. Mutation analysis included direct sequencing and multiplex ligation-dependent probe amplification (MLPA) and was performed in a total of 64 patients from 56 distinct families (28 FPC families, 28 FBC families). In total, 31 patients (48%) originated from FPC families; 24 were FPC patients (77%), 6 had a personal history of BC (19%) and 1 was a suspected carrier (3.2%). The remaining 33 patients (52%) were all female BC patients of whom 31 (94%) had a family history of PC and 2 (6.1%) had a personal history of PC. In none of these 64 patients a PALB2 mutation was found. Therefore, PALB2 does not have a major causal role in familial clustering of PC and BC in non-BRCA1/2 families in the Dutch population.

Matsubayashi H
Familial pancreatic cancer and hereditary syndromes: screening strategy for high-risk individuals.
J Gastroenterol. 2011; 46(11):1249-59 [PubMed] Related Publications
Globally, and almost evenly across nations, a familial disposition can be found in 4-10% of patients with pancreatic cancer (PC). A family history of PC is a risk for this disease and the risk level changes in correlation with the number of affected relatives. Several hereditary syndromes with potential germline mutation also have a high risk for PC; however, little is yet known regarding the genes responsible for familial pancreatic cancer (FPC). Characteristics of FPC cases are similar to those of other familial tumors, including younger onset than in sporadic cases and an ethnic difference (Ashkenazi Jewish > other Caucasian). Other risks resemble those of sporadic cases and include smoking and diabetes mellitus. People with several genetic syndromes, including Peutz-Jeghers syndrome, hereditary pancreatitis, breast-ovarian cancer syndrome, hereditary nonpolyposis colorectal cancer, and familial adenomatous polyposis also have an increased risk of PC. In many countries, but not yet in Japan, screening of these high-risk individuals is now ongoing for the detection of early PC under established familial pancreatic cancer registries. In addition to the ordinary risk factors, such as smoking, diabetes, pancreatitis, cysts, duct ectasia, and intraductal papillary mucinous neoplasm (IPMN), individuals with a family history of PC and hereditary syndromes are expected to be entered into the screening protocol.

Ward CJ, Wu Y, Johnson RA, et al.
Germline PKHD1 mutations are protective against colorectal cancer.
Hum Genet. 2011; 129(3):345-9 [PubMed] Free Access to Full Article Related Publications
The autosomal recessive polycystic kidney disease (ARPKD) gene, PKHD1, has been implicated in the genesis or growth of colorectal adenocarcinoma, as a high level of somatic mutations was found in colorectal tumor tissue. To determine whether carriers of a single PKHD1 mutation are at increased risk of colorectal carcinoma, we assessed the prevalence of the commonest European mutation, T36M. First, we assayed a European cohort of ARPKD patients and found T36M was responsible for 13.1% of mutations. We then investigated two European cohorts with colorectal adenocarcinoma versus two control cohorts of similar age and gender. Screening for the most common PKHD1 mutation, T36M, we detected 15:3,603 (0.42%) controls versus 1:3,767 (0.027%) colorectal cancer individuals, indicating that heterozygous PKHD1 mutations are not a risk factor and are protective (p=0.0002). We also show that the carriage rate for PKHD1 mutations in the European population is higher than previous accepted at 3.2% (1:31 genomes).

Schneider R, Slater EP, Sina M, et al.
German national case collection for familial pancreatic cancer (FaPaCa): ten years experience.
Fam Cancer. 2011; 10(2):323-30 [PubMed] Related Publications
Familial pancreatic cancer (FPC) is a rare hereditary tumor syndrome. The 10-years experience of the national case collection for familial pancreatic cancer of Germany (FaPaCa) is reported. Since 1999 FaPaCa has collected families with at least two first-degree relatives with confirmed pancreatic cancer (PC), who did not fulfill the criteria of other hereditary tumor syndromes. Histopathological verification of tumor diagnoses, and genetic counseling were prerequisites for enrollment of families in FaPaCa. 94 of 452 evaluated families fulfilled the criteria for partaking in FaPaCa. PC represented the sole tumor entity in 38 (40%) families. In 56 families additional tumor types occurred, including breast cancer (n = 28), colon cancer (n = 20) and lung cancer (n = 11). In 70 (74%) families the pattern of inheritance was consistent with an autosomal dominant trait. Compared to the preceding generation, a younger age of onset was observed in the offspring of PC patients (median: 57 vs. 69 years), indicating anticipation. Mutation analyses of BRCA2, PALB2, CDKN2a, RNASEL, STK11, NOD2, CHEK2 and PALLD, revealed deleterious causative germline mutations of BRCA2 and PALB2 in 2 of 70 (3%) and 2 of 41 (4.9%) German FPC families, respectively. Prospective PC screening with EUS, MRI and MRCP detected precancerous lesions (IPMN, multifocal PanIN2/3) or carcinoma in 5.5% (4 of 72) to 12.5% (9 of 72) of individuals at risk, depending on histological verification. Appropriate inclusion of families at high risk for PC in registries, such as FaPaCa, provides a unique and excellent tool to gain clinical and genetic knowledge of FPC. Focused research projects can be conducted most efficiently, when data of different FPC registries are combined.

Hu B, He X, Li A, et al.
Cystogenesis in ARPKD results from increased apoptosis in collecting duct epithelial cells of Pkhd1 mutant kidneys.
Exp Cell Res. 2011; 317(2):173-87 [PubMed] Related Publications
Mutations in the PKHD1 gene result in autosomal recessive polycystic kidney disease (ARPKD) in humans. To determine the molecular mechanism of the cystogenesis in ARPKD, we recently generated a mouse model for ARPKD that carries a targeted mutation in the mouse orthologue of human PKHD1. The homozygous mutant mice display hepatorenal cysts whose phenotypes are similar to those of human ARPKD patients. By littermates of this mouse, we developed two immortalized renal collecting duct cell lines with Pkhd1 and two without. Under nonpermissive culture conditions, the Pkhd1(-/-) renal cells displayed aberrant cell-cell contacts and tubulomorphogenesis. The Pkhd1(-/-) cells also showed significantly reduced cell proliferation and elevated apoptosis. To validate this finding in vivo, we examined proliferation and apoptosis in the kidneys of Pkhd1(-/-) mice and their wildtype littermates. Using proliferation (PCNA and Histone-3) and apoptosis (TUNEL and caspase-3) markers, similar results were obtained in the Pkhd1(-/-) kidney tissues as in the cells. To identify the molecular basis of these findings, we analyzed the effect of Pkhd1 loss on multiple putative signaling regulators. We demonstrated that the loss of Pkhd1 disrupts multiple major phosphorylations of focal adhesion kinase (FAK), and these disruptions either inhibit the Ras/C-Raf pathways to suppress MEK/ERK activity and ultimately reduce cell proliferation, or suppress PDK1/AKT to upregulate Bax/caspase-9/caspase-3 and promote apoptosis. Our findings indicate that apoptosis may be a major player in the cyst formation in ARPKD, which may lead to new therapeutic strategies for human ARPKD.

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