Analysis of GPRC6A variants in different pancreatitis etiologies.

BACKGROUND: The G-protein-coupled receptor Class C Group 6 Member A (GPRC6A) is activated by multiple ligands and is important for the regulation of calcium homeostasis. Extracellular calcium is capable to increase NLRP3 inflammasome activity of the innate immune system and deletion of this proinflammatory pathway mitigated pancreatitis severity in vivo. As such this pathway and the GPRC6A receptor is a reasonable candidate gene for pancreatitis. Here we investigated the prevalence of sequence variants in the GPRC6A locus in different pancreatitis aetiologies. METHODS: We selected 6 tagging SNPs with the SNPinfo LD TAG SNP Selection tool and the functional relevant SNP rs6907580 for genotyping. Cohorts from Germany, further European countries and China with up to 1,124 patients and 1,999 controls were screened for single SNPs with melting curve analysis. RESULTS: We identified an association of rs1606365(G) with alcoholic chronic pancreatitis in a German (odds ratio (OR) 0.76, 95% confidence interval (CI) 0.65-0.89, p = 8 × 10-5) and a Chinese cohort (OR 0.78, 95% CI 0.64-0.96, p = 0.02). However, this association was not replicated in a combined cohort of European patients (OR 1.18, 95% CI 0.99-1.41, p = 0.07). Finally, no association was found with acute and non-alcoholic chronic pancreatitis. CONCLUSIONS: Our results support a potential role of calcium sensing receptors and inflammasome activation in alcoholic chronic pancreatitis development. As the functional consequence of the associated variant is unclear, further investigations might elucidate the relevant mechanisms.

Liver cyst gene knockout in cholangiocytes inhibits cilium formation and Wnt signaling.

Mutations in the PRKCSH, SEC63 and LRP5 genes cause autosomal dominant polycystic liver disease (ADPLD). The proteins products of PRKCSH (alias GIIB) and SEC63 function in protein quality control and processing in the endoplasmic reticulum (ER), while LRP5 is implicated in Wnt/ß-catenin signaling. To identify common denominators in the PLD pathogenesis, we mapped the PLD interactome by affinity proteomics, employing both HEK293T cells and H69 cholangiocytes. Identification of known complex members, such as glucosidase IIA (GIIA) for PRKCSH, and SEC61A1 and SEC61B for SEC63, confirmed the specificity of the analysis. GANAB, encoding GIIA, was very recently identified as an ADPLD gene. The presence of GIIA in the LRP5 complex pinpoints a potential functional connection with PRKCSH. Interestingly, all three PLD-associated protein complexes included filamin A (FLNA), a multifunctional protein described to play a role in ciliogenesis as well as canonical Wnt signalling. As ciliary dysfunction may also contribute to hereditary liver cyst formation, we evaluated the requirement of PRKCSH and SEC63 for ciliogenesis and Wnt signaling. By CRISPR/Cas9 induced knockdown of both ADPLD genes in HEK293T cells and H69 cholangiocytes, we identified that their depletion results in defective ciliogenesis. However, only H69 knockouts displayed reduced Wnt3a activation. Our results suggest that loss of PRKCSH and SEC63 leads to general defects in ciliogenesis, while quenching of the Wnt signaling cascade is cholangiocyte-restricted. Interactions of all three PLD-associated protein complexes with FLNA may mark a common link between the ADPLD proteins and the cystogenic processes driving this disease.

Genome-wide association study identifies inversion in the CTRB1-CTRB2 locus to modify risk for alcoholic and non-alcoholic chronic pancreatitis.

OBJECTIVE: Alcohol-related pancreatitis is associated with a disproportionately large number of hospitalisations among GI disorders. Despite its clinical importance, genetic susceptibility to alcoholic chronic pancreatitis (CP) is poorly characterised. To identify risk genes for alcoholic CP and to evaluate their relevance in non-alcoholic CP, we performed a genome-wide association study and functional characterisation of a new pancreatitis locus. DESIGN: 1959 European alcoholic CP patients and population-based controls from the KORA, LIFE and INCIPE studies (n=4708) as well as chronic alcoholics from the GESGA consortium (n=1332) were screened with Illumina technology. For replication, three European cohorts comprising 1650 patients with non-alcoholic CP and 6695 controls originating from the same countries were used. RESULTS: We replicated previously reported risk loci CLDN2-MORC4, CTRC, PRSS1-PRSS2 and SPINK1 in alcoholic CP patients. We identified CTRB1-CTRB2 (chymotrypsin B1 and B2) as a new risk locus with lead single-nucleotide polymorphism (SNP) rs8055167 (OR 1.35, 95% CI 1.23 to 1.6). We found that a 16.6 kb inversion in the CTRB1-CTRB2 locus was in linkage disequilibrium with the CP-associated SNPs and was best tagged by rs8048956. The association was replicated in three independent European non-alcoholic CP cohorts of 1650 patients and 6695 controls (OR 1.62, 95% CI 1.42 to 1.86). The inversion changes the expression ratio of the CTRB1 and CTRB2 isoforms and thereby affects protective trypsinogen degradation and ultimately pancreatitis risk. CONCLUSION: An inversion in the CTRB1-CTRB2 locus modifies risk for alcoholic and non-alcoholic CP indicating that common pathomechanisms are involved in these inflammatory disorders.

Common single nucleotide polymorphisms in transient receptor potential melastatin type 6 increase the risk for proton pump inhibitor-induced hypomagnesemia: a case-control study.

OBJECTIVE: Proton pump inhibitors (PPIs) are effective drugs for the treatment of gastric acid-related disorders. Serious adverse events are rare for PPIs, but recent data suggest that PPIs cause hypomagnesemia. The aim of this study was to estimate the frequency of PPI-induced hypomagnesemia and to define the risk factors for its development. MATERIALS AND METHODS: A total of 133 chronic users of PPIs were enrolled and patients were distinguished on the basis of their serum Mg concentrations. Common single nucleotide polymorphisms (SNPs) in the candidate gene, transient receptor potential melastatin type 6 (TRPM6), were screened. RESULTS: Seventeen out of 133 patients had PPI-induced hypomagnesemia. The duration of PPI use was longer in those with hypomagnesemia (7.7 vs. 5.2 years). Two common SNPs in TRPM6 (rs3750425 and rs2274924) increased the risk for PPI-induced hypomagnesemia by 5.8-fold. CONCLUSION: We found hypomagnesemia in 13% of PPI users. SNPs in TRPM6 drive the risk of developing hypomagnesemia during chronic PPI use.

Whole-exome sequencing reveals LRP5 mutations and canonical Wnt signaling associated with hepatic cystogenesis.

Polycystic livers are seen in the rare inherited disorder isolated polycystic liver disease (PCLD) and are recognized as the most common extrarenal manifestation in autosomal dominant polycystic kidney disease. Hepatic cystogenesis is characterized by progressive proliferation of cholangiocytes, ultimately causing hepatomegaly. Genetically, polycystic liver disease is a heterogeneous disorder with incomplete penetrance and caused by mutations in PRKCSH, SEC63, PKD1, or PKD2. Genome-wide SNP typing and Sanger sequencing revealed no pathogenic variants in hitherto genes in an extended PCLD family. We performed whole-exome sequencing of DNA samples from two members. A heterozygous variant c.3562C > T located at a highly conserved amino acid position (p.R1188W) in the low density lipoprotein receptor-related protein 5 (LRP5) gene segregated with the disease (logarithm of odds score, 4.62) but was not observed in more than 1,000 unaffected individuals. Screening of LRP5 in a PCLD cohort identified three additional mutations in three unrelated families with polycystic livers (p.V454M, p.R1529S, and p.D1551N), again all undetected in controls. All variants were predicted to be damaging with profound structural effects on LRP5 protein domains. Liver cyst tissue and normal hepatic tissue samples from patients and controls showed abundant LRP5 expression by immunohistochemistry. Functional activity analyses indicated that mutant LRP5 led to reduced wingless signal activation. In conclusion, we demonstrate that germ-line LRP5 missense mutations are associated with hepatic cystogenesis. The findings presented in this study link the pathophysiology of PCLD to deregulation of the canonical wingless signaling pathway.

Identification of Patients With Variants in TPMT and Dose Reduction Reduces Hematologic Events During Thiopurine Treatment of Inflammatory Bowel Disease.

BACKGROUND & AIMS: More than 20% of patients with inflammatory bowel disease (IBD) discontinue thiopurine therapy because of severe adverse drug reactions (ADRs); leukopenia is one of the most serious ADRs. Variants in the gene encoding thiopurine S-methyltransferase (TPMT) alter its enzymatic activity, resulting in higher levels of thiopurine metabolites, which can cause leukopenia. We performed a prospective study to determine whether genotype analysis of TPMT before thiopurine treatment, and dose selection based on the results, affects the outcomes of patients with IBD. METHODS: In a study performed at 30 Dutch hospitals, patients were assigned randomly to groups that received standard treatment (control) or pretreatment screening (intervention) for 3 common variants of TPMT (TPMT*2, TPMT*3A, and TPMT*3C). Patients in the intervention group found to be heterozygous carriers of a variant received 50% of the standard dose of thiopurine (azathioprine or 6-mercaptopurine), and patients homozygous for a variant received 0%-10% of the standard dose. We compared, in an intention-to-treat analysis, outcomes of the intervention (n = 405) and control groups (n = 378) after 20 weeks of treatment. Primary outcomes were the occurrence of hematologic ADRs (leukocyte count < 3.0*10(9)/L or reduced platelet count < 100*10(9)/L) and disease activity (based on the Harvey-Bradshaw Index for Crohn's disease [n = 356] or the partial Mayo score for ulcerative colitis [n = 253]). RESULTS: Similar proportions of patients in the intervention and control groups developed a hematologic ADR (7.4% vs 7.9%; relative risk, 0.93; 95% confidence interval, 0.57-1.52) in the 20 weeks of follow-up evaluation; the groups also had similar mean levels of disease activity (P = .18 for Crohn's disease and P = .14 for ulcerative colitis). However, a significantly smaller proportion of carriers of the TPMT variants in the intervention group (2.6%) developed hematologic ADRs compared with patients in the control group (22.9%) (relative risk, 0.11; 95% confidence interval, 0.01-0.85). CONCLUSIONS: Screening for variants in TPMT did not reduce the proportions of patients with hematologic ADRs during thiopurine treatment for IBD. However, there was a 10-fold reduction in hematologic ADRs among variant carriers who were identified and received a dose reduction, compared with variant carriers who did not, without differences in treatment efficacy. ClinicalTrials.gov number: NCT00521950.

Severe Polycystic Liver Disease Is Not Caused by Large Deletions of the PRKCSH Gene.

BACKGROUND: Isolated polycystic liver disease (ADPLD) is an autosomal dominant Mendelian disorder. Heterozygous PRKCSH (where PRKCSH is protein kinase C substrate 80K-H (80 kDa protein, heavy chain; MIM*177060) mutations are the most frequent cause. Routine molecular testing using Sanger sequencing identifies pathogenic variants in the PRKCSH (15%) and SEC63 (where SEC63 is Saccharomyces cerevisiae homolog 63 (MIM*608648); 6%) genes, but about approximately 80% of patients meeting the clinical ADPLD criteria carry no PRKCSH or SEC63 mutation. Cyst tissue often shows somatic deletions with loss of heterozygosity that was recently recognized as a general mechanism in ADPLD. We hypothesized that germline deletions in the PRKCSH gene may be responsible for hepatic cystogenesis in a significant number of mutation-negative ADPLD patients. METHODS: In this study, we designed a multiplex ligation-dependent probe amplification (MLPA) assay to screen for deletions of PRKCSH exons. Genomic DNA from 60 patients with an ADPLD phenotype was included. RESULTS: MLPA analysis detected no exon deletions in mutation-negative ADPLD patients. CONCLUSION: Large copy number variations on germline level are not present in patients with a clinical diagnosis of ADPLD. MLPA analysis of the PRKCSH gene should not be considered as a diagnostic method to explain hepatic cystogenesis.

Polymorphisms at PRSS1-PRSS2 and CLDN2-MORC4 loci associate with alcoholic and non-alcoholic chronic pancreatitis in a European replication study.

OBJECTIVE: Several genetic risk factors have been identified for non-alcoholic chronic pancreatitis (NACP). A genome-wide association study reported an association of chronic pancreatitis (CP) with variants in PRSS1-PRSS2 (rs10273639; near the gene encoding cationic trypsinogen) and CLDN2-MORC4 loci (rs7057398 in RIPPLY1 and rs12688220 in MORC4). We aimed to refine these findings in a large European cohort. DESIGN: We studied 3062 patients with alcohol-related CP (ACP) or NACP and 5107 controls. Also, 1559 German patients with alcohol-associated cirrhosis or alcohol dependence were included for comparison. We performed several meta-analyses to examine genotype-phenotype relationships. RESULTS: Association with ACP was found for rs10273639 (OR, 0.63; 95% CI 0.55 to 0.72). ACP was also associated with variants rs7057398 and rs12688220 in men (OR, 2.26; 95% CI 1.94 to 2.63 and OR, 2.66; 95% CI 2.21 to 3.21, respectively) and in women (OR, 1.57; 95% CI 1.14 to 2.18 and OR 1.71; 95% CI 1.41 to 2.07, respectively). Similar results were obtained when German patients with ACP were compared with those with alcohol-associated cirrhosis or alcohol dependence. In the overall population of patients with NACP, association with rs10273639 was absent (OR, 0.93; 95% CI 0.79 to 1.01), whereas rs7057398 of the X chromosomal single nucleotide polymorphisms was associated with NACP in women only (OR, 1.32; 95% CI 1.15 to 1.51). CONCLUSIONS: The single-nucleotide polymorphisms rs10273639 at the PRSS1-PRSS2 locus and rs7057398 and rs12688220 at the CLDN2-MORC4 locus are associated with CP and strongly associate with ACP, but only rs7057398 with NACP in female patients.

GST Theta null genotype is associated with an increased risk for ulcerative colitis: a case-control study and meta-analysis of GST Mu and GST Theta polymorphisms in inflammatory bowel disease.

Glutathione S-transferases (GSTs) are important in the detoxification of many compounds, including reactive oxygen species. Polymorphisms in GSTs resulting in a decreased enzyme activity might enhance the risk for inflammatory bowel disease by eliciting a state of oxidative stress. Previous case-control studies showed divergent results and were frequently limited in sample size; therefore we conducted a meta-analysis including results from our case-control study. For the case-control study, we genotyped 552 patients with Crohn's disease (CD), 223 patients with ulcerative colitis (UC) and 972 healthy controls by PCR for functional deletions in GST Mu and GST Theta. Both were not analyzed in recent genome-wide association studies. For the meta-analysis, PubMed, EMBASE and Web of Science were searched. In this meta-analysis, we show an enhanced susceptibility for UC in individuals with the GSTT1null genotype (odds ratio (OR) 2.27, 95% confidence interval (CI) 1.31-3.92). In our case-control study, a reduced risk for CD was seen with the GSTT1null genotype (OR 0.58, 95% CI 0.43-0.77); however, pooled analysis showed an OR of 1.67, 95% CI 0.81-3.45. In this meta-analysis, we showed an increased risk for UC in individuals with the GSTT1null genotype.

Genetic polymorphism 609C>T in NAD(P)H:quinone oxidoreductase 1 enhances the risk of proximal colon cancer.

Gastrointestinal (GI) cancer is responsible for the majority of deaths among all types of cancer. Lifestyle factors may not only be the main risk factor for GI cancer but reactive oxygen species (ROS) may also be involved. The single-nucleotide polymorphisms (SNPs) 609C>T (rs1800566) and 465C>T (rs1131341) in the NAD(P)H: quinone oxidoreductase 1 (NQO1) gene lead to a decline in NQO1 enzyme activity. NQO1 catalyzes the two-electron reduction of quinones to hydroquinones, thereby preventing the formation of ROS. Such polymorphisms in NQO1 may increase the risk of GI cancer. The aim of this study was to evaluate the influence of the SNPs rs1800566 and rs1131341 in the NQO1 gene on the risk of GI cancer in the Netherlands. Real-time polymerase chain reaction techniques were conducted to determine the NQO1 genotypes of 1457 patients with GI cancer and 1457 age- and gender-matched controls in a case-control study. Binary logistic regression analyses showed no statistically significant difference in genotype distributions between patients and controls: odds ratios (ORs) with 95% confidence interval (CI) for rs1800566 were 1.09 (0.93-1.28) and 1.17 (0.77-1.77) for the CT and TT genotypes, respectively. ORs for rs1131341 CT and TT genotypes were 1.21 (0.90-1.63) and 0.54 (0.05-5.94), respectively. For rs1800566, a significant association between the CT genotype and proximal colon cancer was detected (OR=1.60; 95% CI=1.09-2.35). The NQO1*2 T allele of SNP rs1800566 was found associated with an increased risk for proximal colorectal cancer, whereas SNP rs1131341 was rare in our Dutch population and was not associated with GI cancer.

Over-expression of COX-2 mRNA in colorectal cancer.

BACKGROUND: Cyclooxygenase-2 (COX-2, PTGS2) is an enzyme involved in the synthesis of prostaglandins and thromboxanes, which are regulators of biologic processes such as inflammation, cell proliferation and angiogenesis. COX-2 over-expression was reported in many (pre) malignant tissues, but data strongly vary and seem to depend on the methodology used. METHODS: Normal colorectal mucosa and paired cancerous tissue from 60 patients with colorectal cancer was investigated for the levels of COX-2 mRNA by real-time quantitative Polymerase Chain Reaction (qPCR). COX-2 levels were expressed relative to either: tissue weight or levels of the housekeeping genes beta-2 microglobulin (B2M) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). RESULTS: COX-2 mRNA levels, normalized with respect to tissue weight or mRNA levels of the housekeeping genes B2M or GAPDH, were over-expressed in 80%, 70% and 40% of the colorectal tumor tissues, as compared to the paired adjacent normal colorectal mucosa samples, respectively. Highest mRNA COX-2 ratios tumor/normal were measured when expressed per mg tissue (mean ratio 21.6). When normalized with respect to the housekeeping genes B2M or GAPDH, mean tumor/normal ratios were 16.1 and 7.5, respectively. CONCLUSION: Expression of COX-2 mRNA levels per mg tissue is most simple in comparison to normalization with respect to the housekeeping genes B2M or GAPDH. Levels of COX-2 mRNA are found over-expressed in almost 80% of the colorectal tumors, compared to paired adjacent normal colorectal mucosa, suggesting a role of COX-2 as a potential biomarker for cancer risk, whereas inhibitors of COX-2 could be of value in chemoprevention of colon cancer.

ddPCR enables rapid detection of bloodstream infections in patients on home parenteral nutrition: A prospective cohort study.

INTRODUCTION: Chronic intestinal failure patients (CIF) require a central venous access device (CVAD) to administer parenteral nutrition. Most serious complication related to a CVAD is a central line-associated bloodstream infection (CLABSI). The golden standard to diagnose a CLABSI are blood cultures, however, they may require 1-5 days before getting a result. Droplet digital polymerase chain reaction (ddPCR) for the detection of pathogen 16S/28S rRNA is a novel culture-independent molecular technique that has been developed to enhance and expedite infection diagnostics within two and a half hours. In this study, we prospectively compared ddPCR with blood cultures to detect pathogens in whole blood. METHODS: We included adult CIF patients with a clinical suspicion of CLABSI in this prospective single-blinded clinical study. Blood cultures were routinely collected and subsequently two central samples from the CVAD and two peripheral samples from a peripheral venous access point. Primary outcome was the sensitivity and specificity of ddPCR. RESULTS: In total, 75 patients with 126 suspected CLABSI episodes were included, with 80 blood samples from the CVAD and 114 from peripheral veins. The central ddPCR samples showed a sensitivity of 91% (95%CI 77-98), and specificity of 96% (95%CI 85-99). Peripheral ddPCR samples had a sensitivity of 63% (95%CI 46-77) and specificity of 99% (95%CI 93-100). CONCLUSION: ddPCR showed a high sensitivity and specificity relative to blood cultures and enables rapid pathogen detection and characterization. Clinical studies should explore if integrated ddPCR and blood culture outcomes enables a more rapid pathogen guided CLABSI treatment and enhancing patient outcomes.

Barrett associated MHC and FOXF1 variants also increase esophageal carcinoma risk.

Barrett's esophagus, with gastroesophageal reflux disease and obesity as risk factors, predisposes to esophageal adenocarcinoma (EAC). Recently a British genome wide association study identified two Barrett's esophagus susceptibility loci mapping within the major histocompatibility complex (MHC; rs9257809) and closely to the Forkhead-F1 (FOXF1; rs9936833) coding gene. An interesting issue is whether polymorphisms associated with Barrett's esophagus, are also implicated in esophageal carcinoma (EC), and more specifically EAC genesis. Assessing the individual genetic susceptibility can help identify high risk patients more prone to benefit from surveillance programs. Our hypothesis: Barrett associated MHC and FOXF1 variants modify EC risk in Caucasians. In a Dutch case-control study, 431 patients with EC and 605 healthy controls were included. Polymorphisms at chromosomes 6p21 (MHC) and 16q24 (FOXF1) were determined by means of real-time polymerase chain reaction (RT-PCR). Logistic regression analysis was used to calculate odds ratios with 95% confidence intervals. The FOXF1 rs9936833 variant C allele was associated with an increased EAC susceptibility; OR, [95% CI]; 1.21, [0.99-1.47]. A sex-stratified analysis revealed a similar association in males; 1.24 [1.00-1.55]. The variant MHC rs9257809 G allele as well as the MHC heterozygous AG genotype significantly increased ESCC risk; 1.76 [1.16-2.66] and 1.74 [1.08-2.80], respectively. Sex-stratification showed that the variant G allele was especially present in female patients; 2.32 [1.04-5.20]. In conclusion, this study provides evidence that MHC rs9257809 and FOXF1 rs9936833 variants, associated with Barrett's esophagus, also increase ESCC and EAC susceptibility in Caucasians. FOX proteins are transcription factors involved in organogenesis of the GI tract, while MHC haplotypes are strongly associated with smoking behavior, a crucial risk factor for ESCC. Assessing the individual genetic susceptibility can help identify high risk patients more prone to benefit from (Barrett) surveillance programs.

Polymorphisms in alcohol-metabolizing enzymes and esophageal carcinoma susceptibility: a Dutch Caucasian case-control study.

Esophageal cancer (EC), mainly consisting of squamous cell carcinoma (ESCC) in the Eastern world and adenocarcinoma (EAC) in the Western world, is strongly associated with dietary factors such as alcohol use. We aimed to clarify the modifying role in EC etiology in Caucasians of functional genotypes in alcohol-metabolizing enzymes. In all, 351 Caucasian patients with EC and 430 matched controls were included and polymorphisms in CYP2E1, ADH and near ALDH2 genes were determined. In contrast to the results on ESCC in mainly Asian studies, we found that functional genotypes of alcohol-metabolizing enzymes were not significantly associated with EAC or ESCC in an European population.

No role for glutathione S-transferase genotypes in Caucasian esophageal squamous cell or adenocarcinoma etiology: an European case-control study.

BACKGROUND: Identifying and monitoring high-risk patients can aid the prevention of esophageal cancer (EC). The interaction of environmental risk factor exposure and genetic susceptibility may contribute to the etiology of EC. Biotransformation enzymes such as Glutathione S-Transferases (GSTs ) detoxify mutagenic and genotoxic compounds and therefore control the rate of detoxification of carcinogens. Functional polymorphisms in the genes coding for GSTs alter their enzyme activity in vitro, and were reported to modify EC risk in Asians. We hypothesized that altered enzyme activity GST genotypes influence the susceptibility for esophageal adeno- (EAC) and squamous cell carcinoma (ESCC) in Caucasians. METHODS: We performed a case-control study including 440 Caucasian patients with EC and 592 healthy Caucasian controls matched for age and sex. Functional polymorphisms were selected and genotypes were determined in GST classes Alpha, Mu, Theta and Pi by means of polymerase chain reaction. Genotypes were classified into predicted high, intermediate and low enzyme activity categories based on in vitro activity data. The distribution of the activity genotypes were compared between patients with EAC or ESCC, and controls. Odds ratios (OR) with 95% confidence intervals (CI) were calculated by logistic regression analyses. Gene-gene interactions were tested and for comparison purposes, the predicted low and intermediate activity genotypes were combined. Genotypes with similar risks for EAC or ESCC were combined and analyzed for multiplicative effects. RESULTS: Our analyses includes 327 patients with EAC and 106 patients with ESCC. Low or intermediate activity enzyme genotypes for GSTM1, GSTA1, GSTP1 I105V and A114V as well as for GSTT1, did not significantly modify the risk for ESCC or EAC in our Dutch population. CONCLUSION: Functional genotypes in GST genes are not involved in EAC or ESCC susceptibility in Caucasians, in contrast to results on ESCC from Asia or Africa.

Functional profiles of SCN9A variants in dorsal root ganglion neurons and superior cervical ganglion neurons correlate with autonomic symptoms in small fibre neuropathy.

Patients with small fibre neuropathy typically manifest pain in distal extremities and severe autonomic dysfunction. However, occasionally patients present with minimal autonomic symptoms. The basis for this phenotypic difference is not understood. Sodium channel Na(v)1.7, encoded by the SCN9A gene, is preferentially expressed in the peripheral nervous system within sensory dorsal root ganglion and sympathetic ganglion neurons and their small diameter peripheral axons. We recently reported missense substitutions in SCN9A that encode functional Na(v)1.7 variants in 28% of patients with biopsy-confirmed small fibre neuropathy. Two patients with biopsy-confirmed small fibre neuropathy manifested minimal autonomic dysfunction unlike the other six patients in this series, and both of these patients carry the Na(v)1.7/R185H variant, presenting the opportunity to compare variants associated with extreme ends of a spectrum from minimal to severe autonomic dysfunction. Herein, we show by voltage-clamp that R185H variant channels enhance resurgent currents within dorsal root ganglion neurons and show by current-clamp that R185H renders dorsal root ganglion neurons hyperexcitable. We also show that in contrast, R185H variant channels do not produce detectable changes when studied by voltage-clamp within sympathetic neurons of the superior cervical ganglion, and have no effect on the excitability of these cells. As a comparator, we studied the Na(v)1.7 variant I739V, identified in three patients with small fibre neuropathy characterized by severe autonomic dysfunction as well as neuropathic pain, and show that this variant impairs channel slow inactivation within both dorsal root ganglion and superior cervical ganglion neurons, and renders dorsal root ganglion neurons hyperexcitable and superior cervical ganglion neurons hypoexcitable. Thus, we show that R185H, from patients with minimal autonomic dysfunction, does not produce detectable changes in the properties of sympathetic ganglion neurons, while I739V, from patients with severe autonomic dysfunction, has a profound effect on excitability of sympathetic ganglion neurons.

Celecoxib and tauro-ursodeoxycholic acid co-treatment inhibits cell growth in familial adenomatous polyposis derived LT97 colon adenoma cells.

Chemoprevention would be a desirable strategy to avoid duodenectomy in patients with familial adenomatous polyposis (FAP) suffering from duodenal adenomatosis. We investigated the in vitro effects on cell proliferation, apoptosis, and COX-2 expression of the potential chemopreventives celecoxib and tauro-ursodeoxycholic acid (UDCA). HT-29 colon cancer cells and LT97 colorectal micro-adenoma cells derived from a patient with FAP, were exposed to low dose celecoxib and UDCA alone or in combination with tauro-cholic acid (CA) and tauro-chenodeoxycholic acid (CDCA), mimicking bile of FAP patients treated with UDCA. In HT-29 cells, co-treatment with low dose celecoxib and UDCA resulted in a decreased cell growth (14-17%, p<0.01). A more pronounced decrease (23-27%, p<0.01) was observed in LT97 cells. Cell growth of HT-29 cells exposed to 'artificial bile' enriched with UDCA, was decreased (p<0.001), either in the absence or presence of celecoxib. In LT97 cells incubated with 'artificial bile' enriched with UDCA, cell growth was decreased only in the presence of celecoxib (p<0.05). No clear evidence was found for involvement of proliferating cell nuclear antigen, caspase-3, or COX-2 in the cellular processes leading to the observed changes in cell growth. In conclusion, co-treatment with low dose celecoxib and UDCA has growth inhibitory effects on colorectal adenoma cells derived from a patient with FAP, and further research on this combination as promising chemopreventive strategy is desired.

Pain perception is altered by a nucleotide polymorphism in SCN9A.

The gene SCN9A is responsible for three human pain disorders. Nonsense mutations cause a complete absence of pain, whereas activating mutations cause severe episodic pain in paroxysmal extreme pain disorder and primary erythermalgia. This led us to investigate whether single nucleotide polymorphisms (SNPs) in SCN9A were associated with differing pain perception in the general population. We first genotyped 27 SCN9A SNPs in 578 individuals with a radiographic diagnosis of osteoarthritis and a pain score assessment. A significant association was found between pain score and SNP rs6746030; the rarer A allele was associated with increased pain scores compared to the commoner G allele (P = 0.016). This SNP was then further genotyped in 195 pain-assessed people with sciatica, 100 amputees with phantom pain, 179 individuals after lumbar discectomy, and 205 individuals with pancreatitis. The combined P value for increased A allele pain was 0.0001 in the five cohorts tested (1277 people in total). The two alleles of the SNP rs6746030 alter the coding sequence of the sodium channel Nav1.7. Each was separately transfected into HEK293 cells and electrophysiologically assessed by patch-clamping. The two alleles showed a difference in the voltage-dependent slow inactivation (P = 0.042) where the A allele would be predicted to increase Nav1.7 activity. Finally, we genotyped 186 healthy females characterized by their responses to a diverse set of noxious stimuli. The A allele of rs6746030 was associated with an altered pain threshold and the effect mediated through C-fiber activation. We conclude that individuals experience differing amounts of pain, per nociceptive stimulus, on the basis of their SCN9A rs6746030 genotype.

Germline mutations in PRKCSH are associated with autosomal dominant polycystic liver disease.

Polycystic liver disease (PCLD, OMIM 174050) is a dominantly inherited condition characterized by the presence of multiple liver cysts of biliary epithelial origin. Fine mapping established linkage to marker D19S581 (Z(max) = 9.65; theta = 0.01) in four large Dutch families with PCLD. We identified a splice-acceptor site mutation (1138-2A-->G) in PRKCSH in three families, and a splice-donor site mutation (292+1G-->C) in PRKCSH segregated completely with PCLD in another family. The protein encoded by PRKCSH, here named hepatocystin, is predicted to localize to the endoplasmic reticulum. These findings establish germline mutations in PRKCSH as the probable cause of PCLD.

Heterozygosity of ALG9 in Association with Autosomal Dominant Polycystic Liver Disease.

α-1,2-mannosyltransferase (ALG9) germline variants are linked to autosomal dominant polycystic kidney disease (ADPKD). Many individuals affected with ADPKD possess polycystic livers as a common extrarenal manifestation. We performed whole exome sequencing in a female with autosomal dominant polycystic liver disease (ADPLD) without kidney cysts and established the presence of a heterozygous missense variant (c.677G>C p.(Gly226Ala)) in ALG9. In silico pathogenicity prediction and 3D protein modeling determined this variant as pathogenic. Loss of heterozygosity is regularly seen in liver cyst walls. Immunohistochemistry indicated the absence of ALG9 in liver tissue from this patient. ALG9 expression was absent in cyst wall lining from ALG9- and PRKCSH-caused ADPLD patients but present in the liver cyst lining derived from an ADPKD patient with a PKD2 variant. Thus, heterozygous pathogenic variants in ALG9 are also associated with ADPLD. Somatic loss of heterozygosity of the ALG9 enzyme was seen in the ALG9 patient but also in ADPLD patients with a different genetic background. This expanded the phenotypic spectrum of ADPLD to ALG9.