Trypsinogen copy number mutations in patients with idiopathic chronic pancreatitis

Classification of PRSS1 variants responsible for chronic pancreatitis: An expert perspective from the Franco-Chinese GREPAN study group

BACKGROUND

PRSS1 was the first reported chronic pancreatitis (CP) gene. The existence of both gain-of-function (GoF) and gain-of-proteotoxicity (GoP) pathological PRSS1 variants, together with the fact that PRSS1 variants have been identified in CP subtypes spanning the range from monogenic to multifactorial, has made the classification of PRSS1 variants very challenging.

METHODS

All currently reported PRSS1 variants (derived primarily from two databases) were manually reviewed with respect to their clinical genetics, functional analysis and population allele frequency. They were classified by variant type and pathological mechanism within the framework of our recently proposed ACMG/AMP guidelines-based seven-category system.

RESULTS

The total number of distinct germline PRSS1 variants included for analysis was 100, comprising 3 copy number variants (CNVs), 12 5' and 3' variants, 19 intronic variants, 5 nonsense variants, 1 frameshift deletion variant, 6 synonymous variants, 1 in-frame duplication, 3 gene conversions and 50 missense variants. Based upon a combination of clinical genetic and functional analysis, population data and in silico analysis, we classified 26 variants (all 3 CNVs, the in-frame duplication, all 3 gene conversions and 19 missense) as "pathogenic", 3 variants (missense) as "likely pathogenic", 5 variants (four missense and one promoter) as "predisposing", 13 variants (all missense) as "unknown significance", 2 variants (missense) as "likely benign", and all remaining 51 variants as "benign".

CONCLUSIONS

We describe an expert classification of the 100 PRSS1 variants reported to date. The results have immediate implications for reclassifying many ClinVar-registered PRSS1 variants as well as providing optimal guidelines/standards for reporting PRSS1 variants.

The PRSS3P2 and TRY7 deletion copy number variant modifies risk for chronic pancreatitis

BACKGROUND

PRSS1 and PRSS2 constitute the only functional copies of a tandemly-arranged five-trypsinogen-gene cluster (i.e., PRSS1, PRSS3P1, PRSS3P2, TRY7 and PRSS2) on chromosome 7q35. Variants in PRSS1 and PRSS2, including missense and copy number variants (CNVs), have been reported to predispose to or protect against chronic pancreatitis (CP). We wondered whether a common trypsinogen pseudogene deletion CNV (that removes two of the three trypsinogen pseudogenes, PRSS3P2 and TRY7) might be associated with CP causation/predisposition.

METHODS

We analyzed the common PRSS3P2 and TRY7 deletion CNV in a total of 1536 CP patients and 3506 controls from France, Germany, India and Japan by means of quantitative fluorescent multiplex polymerase chain reaction.

RESULTS

We demonstrated that the deletion CNV variant was associated with a protective effect against CP in the French, German and Japanese cohorts whilst a trend toward the same association was noted in the Indian cohort. Meta-analysis under a dominant model yielded a pooled odds ratio (OR) of 0.68 (95% confidence interval (CI) 0.52-0.89; p = 0.005) whereas an allele-based meta-analysis yielded a pooled OR of 0.84 (95% CI 0.77-0.92; p = 0.0001). This protective effect is explicable by reference to the recent finding that the still functional PRSS3P2/TRY7 pseudogene enhancers upregulate pancreatic PRSS2 expression.

CONCLUSIONS

The common PRSS3P2 and TRY7 deletion CNV was associated with a reduced risk for CP. This finding provides additional support for the emerging view that dysregulated PRSS2 expression represents a discrete mechanism underlying CP predisposition or protection.

WITHDRAWN: Clinical interpretation of PRSS1 gene variants in patients with pancreatitis

The Publisher regrets that this article is an accidental duplication of an article that has already been published in Clinics and Research in Hepatology and Gastroenterology, Volume 45, Issue 1, 2021, 101497. https://doi.org/10.1016/j.clinre.2020.07.004. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

Single-Cell Transcriptome Analysis Reveals the Role of Pancreatic Secretome in COVID-19 Associated Multi-organ Dysfunctions

The SARS-CoV-2 infection affects the lungs, heart, kidney, intestine, olfactory epithelia, liver, and pancreas and brings forward multi-organ dysfunctions (MODs). However, mechanistic details of SARS-CoV-2-induced MODs are unclear. Here, we have investigated the role of pancreatic secretory proteins to mechanistically link COVID-19 with MODs using single-cell transcriptome analysis. Secretory proteins were identified using the Human Protein Atlas. Gene ontology, pathway, and disease enrichment analyses were used to highlight the role of upregulated pancreatic secretory proteins (secretome). We show that SARS-CoV-2 infection shifts the expression profile of pancreatic endocrine cells to acinar and ductal cell-specific profiles, resulting in increased expression of acinar and ductal cell-specific genes. Among all the secretory proteins, the upregulated expression of IL1B, AGT, ALB, SPP1, CRP, SERPINA1, C3, TFRC, TNFSF10, and MIF was mainly associated with disease of diverse organs. Extensive literature and experimental evidence are used to validate the association of the upregulated pancreatic secretome with the coagulation cascade, complement activation, renin-angiotensinogen system dysregulation, endothelial cell injury and thrombosis, immune system dysregulation, and fibrosis. Our finding suggests the influence of an upregulated secretome on multi-organ systems such as nervous, cardiovascular, immune, digestive, and urogenital systems. Our study provides evidence that an upregulated pancreatic secretome is a possible cause of SARS-CoV-2-induced MODs. This finding may have a significant impact on the clinical setting regarding the prevention of SARS-CoV-2-induced MODs.

Trypsinogen (PRSS1 and PRSS2) gene dosage correlates with pancreatitis risk across genetic and transgenic studies: a systematic review and re-analysis

Trypsinogen (PRSS1, PRSS2) copy number gains and regulatory variants have both been proposed to elevate pancreatitis risk through a gene dosage effect (i.e., by increasing the expression of wild-type protein). However, to date, their impact on pancreatitis risk has not been thoroughly evaluated whilst the underlying pathogenic mechanisms remain to be explicitly investigated in mouse models. Genetic studies of the rare trypsinogen duplication and triplication copy number variants (CNVs), and the common rs10273639C variant, were collated from PubMed and/or ClinVar. Mouse studies that analyzed the influence of a transgenically expressed wild-type human PRSS1 or PRSS2 gene on the development of pancreatitis were identified from PubMed. The genetic effects of the different risk genotypes, in terms of odds ratios, were calculated wherever appropriate. The genetic effects of the rare trypsinogen duplication and triplication CNVs were also evaluated by reference to their associated disease subtypes. We demonstrate a positive correlation between increased trypsinogen gene dosage and pancreatitis risk in the context of the rare duplication and triplication CNVs, and between the level of trypsinogen expression and disease risk in the context of the heterozygous and homozygous rs10273639C-tagged genotypes. We retrospectively identify three mouse transgenic studies that are informative in relation to the pathogenic mechanism underlying the trypsinogen gene dosage effect in pancreatitis. Trypsinogen gene dosage correlates with pancreatitis risk across genetic and transgenic studies, highlighting the fundamental role of dysregulated expression of wild-type trypsinogen in the etiology of pancreatitis. Specifically downregulating trypsinogen expression in the pancreas may serve as a potential therapeutic and/or prevention strategy for pancreatitis.

The unfolded protein response: An emerging therapeutic target for pancreatitis and pancreatic ductal adenocarcinoma

Pancreatitis is a debilitating disease involving inflammation and fibrosis of the exocrine pancreas. Recurrent or chronic forms of pancreatitis are a significant risk factor for pancreatic ductal adenocarcinoma. While genetic factors have been identified for both pathologies, environmental stresses play a large role in their etiology. All cells have adapted mechanisms to handle acute environmental stress that alters energy demands. A common pathway involved in the stress response involves endoplasmic reticulum stress and the unfolded protein response (UPR). While rapidly activated by many external stressors, in the pancreas the UPR plays a fundamental biological role, likely due to the high protein demands in acinar cells. Despite this, increased UPR activity is observed in response to acute injury or following exposure to risk factors associated with pancreatitis and pancreatic cancer. Studies in animal and cell cultures models show the importance of affecting the UPR in the context of both diseases, and inhibitors have been developed for several specific mediators of the UPR. Given the importance of the UPR to normal acinar cell function, efforts to affect the UPR in the context of disease must be able to specifically target pathology vs. physiology. In this review, we highlight the importance of the UPR to normal and pathological conditions of the exocrine pancreas. We discuss recent studies suggesting the UPR may be involved in the initiation and progression of pancreatitis and PDAC, as well as contributing to chemoresistance that occurs in pancreatic cancer. Finally, we discuss the potential of targeting the UPR for treatment.

Scale and Scope of Gene-Alcohol Interactions in Chronic Pancreatitis: A Systematic Review

BACKGROUND

Excessive alcohol consumption has long been known to be the primary cause of chronic pancreatitis (CP) but genetic risk factors have been increasingly identified over the past 25 years. The scale and scope of gene-alcohol interactions in CP nevertheless remain unclear.

METHODS

All studies that had obtained genetic variant data concurrently on alcoholic CP (ACP) patients, non-ACP (NACP) patients and normal controls were collated. Employing normal controls as a common baseline, paired OR_ACP and OR_NACP (odds ratios associated with ACP and NACP, respectively) values were calculated and used to assess gene-alcohol interactions.

RESULTS

Thirteen variants involving PRSS1, SPINK1, CTRC, CLDN2, CPA1, CEL and CTRB1-CTRB2, and varying from very rare to common, were collated. Seven variants had an OR_ACP > OR_NACP, which was regarded as an immediate indicator of gene-alcohol interactions in CP. Variants with an OR_ACP < OR_NACP were also found to interact with alcohol consumption by virtue of their impact on age at first pancreatitis symptoms in ACP.

CONCLUSIONS

This study revealed evidence for extensive gene-alcohol interactions in CP. Our findings lend support to the hypothesis that alcohol affects the expression of genetically determined CP and highlight a predominant role of weak-effect variants in the development of ACP.

Clinical interpretation of PRSS1 variants in patients with pancreatitis

Since the description of the PRSS1 gene encoding the cationic trypsinogen as being involved in dominant hereditary pancreatitis, more than 50 PRSS1 variants have been reported. Among the PRSS1 variants that have been classified as pathogenic, some have a high penetrance and others have a low penetrance. Assessing the clinical relevance of PRSS1 variants is often complicated in the absence of functional evidence and interpretation of rare variants is not very easy in clinical practice. The aim of this study was to review the different variants identified in the PRSS1 gene and to classify them according to their degree of deleterious effect. This classification was based on the results of several in vitro experiments and on population data, in comparing the allelic frequency of each variant in patients with pancreatitis and in unaffected individuals. This review should help geneticists and clinicians in charge of patient's care and genetic counseling to interpret molecular results.

Role of the Common PRSS1-PRSS2 Haplotype in Alcoholic and Non-Alcoholic Chronic Pancreatitis: Meta- and Re-Analyses

The association between a common PRSS1-PRSS2 haplotype and alcoholic chronic pancreatitis (ACP), which was revealed by the first genome-wide association study of chronic pancreatitis (CP), has been consistently replicated. However, the association with non-ACP (NACP) has been controversial. Herein, we sought to clarify this basic issue by means of an allele-based meta-analysis of currently available studies. We then used studies informative for genotype distribution to explore the biological mechanisms underlying the association data and to test for gene-environment interaction between the risk haplotype and alcohol consumption by means of a re-analysis. A literature search was conducted to identify eligible studies. A meta-analysis was performed using the Review Manager software. The association between the risk genotypes and NACP or ACP was tested for the best-fitting genetic model. Gene-environment interaction was estimated by both case-only and multinomial approaches. Five and eight studies were employed for the meta-analysis of ACP and NACP findings, respectively. The risk allele was significantly associated with both ACP (pooled odds ratio (OR) 1.67, 95% confidence interval (CI) 1.56–1.78; p < 0.00001) and NACP (pooled OR 1.28, 95% CI 1.17–1.40; p < 0.00001). Consistent with a dosage effect of the risk allele on PRSS1/PRSS2 mRNA expression in human pancreatic tissue, both ACP and NACP association data were best explained by an additive genetic model. Finally, the risk haplotype was found to interact synergistically with alcohol consumption.

Characterization of CEL-DUP2: Complete duplication of the carboxyl ester lipase gene is unlikely to influence risk of chronic pancreatitis

BACKGROUND/OBJECTIVES

Carboxyl ester lipase is a pancreatic enzyme encoded by CEL, an extremely polymorphic human gene. Pathogenic variants of CEL either increases the risk for chronic pancreatitis (CP) or cause MODY8, a syndrome of pancreatic exocrine and endocrine dysfunction. Here, we aimed to characterize a novel duplication allele of CEL (CEL-DUP2) and to investigate whether it associates with CP or pancreatic cancer.

METHODS

The structure of CEL-DUP2 was determined by a combination of Sanger sequencing, DNA fragment analysis, multiplex ligation-dependent probe amplification and whole-genome sequencing. We developed assays for screening of CEL-DUP2 and analyzed cohorts of idiopathic CP, alcoholic CP and pancreatic cancer. CEL protein expression was analyzed by immunohistochemistry.

RESULTS

CEL-DUP2 consists of an extra copy of the complete CEL gene. The allele has probably arisen from non-allelic, homologous recombination involving the adjacent pseudogene of CEL. We found no association between CEL-DUP2 carrier frequency and CP in cohorts from France (cases/controls: 2.5%/2.4%; P = 1.0), China (10.3%/8.1%; P = 0.08) or Germany (1.6%/2.3%; P = 0.62). Similarly, no association with disease was observed in alcohol-induced pancreatitis (Germany: 3.2%/2.3%; P = 0.51) or pancreatic cancer (Norway; 2.5%/3.2%; P = 0.77). Notably, the carrier frequency of CEL-DUP2 was more than three-fold higher in Chinese compared with Europeans. CEL protein expression was similar in tissues from CEL-DUP2 carriers and controls.

CONCLUSIONS

Our results support the contention that the number of CEL alleles does not influence the risk of pancreatic exocrine disease. Rather, the pathogenic CEL variants identified so far involve exon 11 sequence changes that substantially alter the protein's tail region.

Recurrent Acute Pancreatitis: International State-of-the-Science Conference With Recommendations

Recurrent acute pancreatitis (RAP) is a clinically significant problem globally. The etiology remains unclear in approximately 10% to 15% of patients despite a thorough workup. Data on natural history and efficacy of treatments are limited. We aimed to establish criteria for diagnosis, evaluate the causative factors, and arrive at a consensus on the appropriate workup and management of patients with RAP. The organizing committee was formed, and a set of questions was developed based on the current evidence, controversies, and topics that needed further research. After a vetting process, these topics were assigned to a group of experts from around the world with special interest in RAP. Data were presented as part of a workshop on RAP organized as a part of the annual meeting of the America Pancreatic Association. Pretest and Posttest questions were administered, and the responses were tabulated by the current Grades of Recommendation Assessment, Development and Evaluation system. The consensus guidelines were established in the format of a diagnostic algorithm. Several deficiencies were identified with respect to data on etiology, treatment efficacies, and areas that need immediate research.

International consensus statements on early chronic Pancreatitis. Recommendations from the working group for the international consensus guidelines for chronic pancreatitis in collaboration with The International Association of Pancreatology, American Pancreatic Association, Japan Pancreas Society, PancreasFest Working Group and European Pancreatic Club

BACKGROUND

Chronic pancreatitis (CP) is a progressive inflammatory disorder currently diagnosed by morphologic features. In contrast, an accurate diagnosis of Early CP is not possible using imaging criteria alone. If this were possible and early treatment instituted, the later, irreversible features and complications of CP could possibly be prevented.

METHOD

An international working group supported by four major pancreas societies (IAP, APA, JPS, and EPC) and a PancreasFest working group sought to develop a consensus definition and diagnostic criteria for Early CP. Ten statements (S1-10) concerning Early CP were used to gauge consensus on the Early CP concept using anonymous voting with a 9 point Likert scale. Consensus required an alpha ≥0.80.

RESULTS

No consensus statement could be developed for a definition of Early-CP or diagnostic criteria. There was consensus on 5 statements: (S2) The word "Early" in early chronic pancreatitis is used to describe disease state, not disease duration. (S4) Early CP defines a stage of CP with preserved pancreatic function and potentially reversible features. (S8) Genetic variants are important risk factors for Early CP and can add specificity to the likely etiology, but they are neither necessary nor sufficient to make a diagnosis. (S9) Environmental risk factors can provide evidence to support the diagnosis of Early CP, but are neither necessary nor sufficient to make a diagnosis. (S10) The differential diagnosis for Early CP includes other disorders with morphological and functional features that overlap with CP.

CONCLUSIONS

Morphology based diagnosis of Early CP is not possible without additional information. New approaches to the accurate diagnosis of Early CP will require a mechanistic definition that considers risk factors, biomarkers, clinical context and new models of disease. Such a definition will require prospective validation.

PRSS1 (R122H) mutation in an Indian family with low penetrance is associated with pancreatitis phenotype

Mutations in PRSS1 gene namely R122H and N29I cause hereditary pancreatitis. They are autosomal dominant with a high penetrance (80%) reported in North American, North-east Asian, and North European ethnicities. However, the mutations are reportedly absent in Indian, African, and South American ethnicities. We report here for the first time a family from India that is positive for R122H mutation in the PRSS1 gene. The proband is symptomatic with chronic pancreatitis, however, the father although heterozygous for R122H is asymptomatic.

Genetic Risk in Chronic Pancreatitis: The Trypsin-Dependent Pathway

Genetic investigations have provided unique insight into the mechanism of chronic pancreatitis in humans and firmly established that uncontrolled trypsin activity is a central pathogenic factor. Mutations in the PRSS1, SPINK1, and CTRC genes promote increased activation of trypsinogen to trypsin by stimulation of autoactivation or by impairing protective trypsinogen degradation and/or trypsin inhibition. Here we review key genetic and biochemical features of the trypsin-dependent pathological pathway in chronic pancreatitis.

PRSS1, SPINK1, CFTR, and CTRC Pathogenic Variants in Korean Patients With Idiopathic Pancreatitis

BACKGROUND

This study aimed to identify pathogenic variants of PRSS1, SPINK1, CFTR, and CTRC genes in Korean patients with idiopathic pancreatitis.

METHODS

The study population consisted of 116 Korean subjects (65 males, 51 females; mean age, 30.4 yr, range, 1-88 yr) diagnosed with idiopathic chronic pancreatitis (ICP), idiopathic recurrent acute pancreatitis (IRAP), or idiopathic acute pancreatitis (IAP). We analyzed sequences of targeted regions in the PRSS1, SPINK1, CFTR, and CTRC genes, copy numbers of PRSS1 and SPINK1, and clinical data from medical records.

RESULTS

We identified three types of pathogenic PRSS1 variants in 11 patients, including p.N29I (n=1), p.R122H (n=1), and p.G208A (n=9). Sixteen patients exhibited heterozygous pathogenic variants of SPINK1, including c.194+2T>C (n=12), p.N34S (n=3), and a novel pathogenic splicing variation c.194+1G>A. A heterozygous CFTR p.Q1352H pathogenic variant was detected in eight patients. One patient carried a heterozygous CTRC p.P249L pathogenic variant, which is a known high-risk variant for pancreatitis. All patients had normal PRSS1 and SPINK1 gene copy numbers. Weight loss occurred more frequently in patients carrying the p.G208A pathogenic variant, while pancreatic duct stones occurred more frequently in patients with the c.194+2T>C pathogenic variant.

CONCLUSIONS

Pathogenic variants of PRSS1, SPINK1, and CFTR were associated with idiopathic pancreatitis, while pathogenic variants of CTRC were not. Copy number variations of PRSS1 and SPINK1 were not detected.

Genetic Analysis of Japanese Children With Acute Recurrent and Chronic Pancreatitis

OBJECTIVES

Causes of acute recurrent pancreatitis (ARP) or chronic pancreatitis (CP) are sometimes difficult to determine in children. In such patients, genetic analysis may prove helpful. The present study analyzed mutations of cationic trypsinogen (PRSS1), serine protease inhibitor Kazal type 1 (SPINK1), chymotrypsin C (CTRC), and carboxypeptidase A1 (CPA1) and investigated the clinical features of children with these mutations.

METHODS

Genetic analyses of mutations in these 4 genes were conducted in 128 patients with ARP or CP. Characteristics of the patients showing mutations were investigated using medical records.

RESULTS

Fifty of the 128 (39.1%) subjects had at least 1 mutation (median age at onset, 7.6 years). Abdominal pain was the presenting symptom of pancreatitis in 48 of the 50 patients (96%). Fifteen of those 50 patients (30.0%) had a family history of pancreatitis. Gene mutations were present in PRSS1 in 26 patients, SPINK1 in 23, CTRC in 3, and CPA1 in 5. In the 31 patients with mutations in SPINK1, CTRC, or CPA1, 16 (51.6%) had homozygous or heterozygous mutations with other mutations. Three patients underwent surgery and another 4 patients underwent endoscopy to manage ARP or CP. Although 3 of the 7 patients complained of mild abdominal pain, none of those 7 patients experienced any obvious episode of ARP after treatment.

CONCLUSIONS

In pediatric patients with idiopathic ARP and CP, genetic analysis is useful for identifying the cause of pancreatitis. Early endoscopic or surgical treatment prevents ARP by extending the interval between episodes of pancreatitis in this population.

Extensive molecular analysis suggested the strong genetic heterogeneity of idiopathic chronic pancreatitis

Rationale: Genetic features of Chronic Pancreatitis (CP) have been extensively investigated mainly testing genes associated to the trypsinogen activation pathway. However, different molecular pathways involving other genes may be implicated in CP pathogenesis. Objectives: 80 patients with Idiopathic CP were investigated using Next Generation Sequencing approach with a panel of 70 genes related to six different pancreatic pathways: premature activation of trypsinogen; modifier genes of Cystic Fibrosis phenotype; pancreatic secretion and ion homeostasis; Calcium signalling and zymogen granules exocytosis; autophagy; autoimmune pancreatitis related genes. Results: We detected mutations in 34 out of 70 genes examined; 64/80 patients (80.0%) were positive for mutations in one or more genes, 16/80 patients (20.0%) had no mutations. Mutations in CFTR were detected in 32/80 patients (40.0%) and 22 of them exhibited at least one mutation in genes of other pancreatic pathways. Of the remaining 48 patients, 13/80 (16.3%) had mutations in genes involved in premature activation of trypsinogen and 19/80 (23.8%) had mutations only in genes of the other pathways: 38/64 patients positive for mutations showed variants in two or more genes (59.3%). Conclusions: Our data, although to be extended with functional analysis of novel mutations, suggest a high rate of genetic heterogeneity in chronic pancreatitis and that trans-heterozygosity may predispose to the idiopathic CP phenotype.

Framework for interpretation of trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis

Early intracellular premature trypsinogen activation was interpreted as the key initiator of pancreatitis. When the balance in the homeostasis of trypsin and antitrypsin system is disequilibrated, elevated aggressive enzymes directly attack the pancreatic tissue, which leads to pancreatic destruction and inflammation. However, trypsin alone is not enough to cause complications in pancreatitis, which may play a crucial role in modulating signaling events in the initial phase of the disease. NFκB activation is the major inflammatory pathway involved in the occurrence and development of pancreatitis and it can be induced by intrapancreatic activation of trypsinogen. Synthesis of trypsinogen occurs in endoplasmic reticulum (ER), and ER stress is an important early acinar cell event. Components of ER stress response are known to be able to trigger cell death as well as NFκB signaling cascade. The strongest evidence supporting the trypsin-centered theory is that gene mutations, which lead to the generation of more trypsin, or reduce the activity of trypsin inhibitors or trypsin degradation, are associated with pancreatitis. Thus, trypsin-antitrypsin imbalance may be the first step leading to pancreatic autodigestion and inducing other pathways. Continued experimental studies are necessary to determine the specific relationships between trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis. In this article, we review the latest advances that contributed to the understanding of the basic mechanisms behind the occurrence and development of pancreatitis with a focus on the interpretation of trypsin-antitrypsin imbalance and their relationships with other inflammation pathways. We additionally highlight genetic predispositions to pancreatitis and possible mechanisms associated with them.

Genetic and phenotypic heterogeneity in tropical calcific pancreatitis

Tropical calcific pancreatitis (TCP) is a form of chronic non-alcoholic pancreatitis initially reported in the developing parts of the tropical world. The clinical phenotype of TCP has undergone marked changes since its first description in 1968. The disease is now seen in relatively older people with less severe symptoms. In addition, there are varying reports on the proportion of cases presenting with imaging abnormalities like calcification, ductal dilation, and glandular atrophy. Significant progress has also been made in understanding the etiopathology of TCP. The role of malnutrition and cassava toxicity in its pathogenesis is disproven and few studies have focused on the role of micronutrient deficiency and oxidative stress in the etiopathogenesis of TCP. Emerging evidence support an important role for genetic risk factors in TCP. Several studies have shown that, rather than mutations in trypsinogens, variants in serine protease inhibitor kazal type 1, cathepsin B, chymotrypsin C, cystic fibrosis transmembrane regulator, and carboxypeptidase A1, predict risk of TCP. These studies also provided evidence of mutational heterogeneity between TCP and chronic pancreatitis in Western populations. The current review summarizes recent advances that have implications in the understanding of the pathophysiology and thus, heterogeneity in genotype-phenotype correlations in TCP.

Human cationic trypsinogen (PRSS1) variants and chronic pancreatitis

Variations in the serine protease 1 (PRSS1) gene encoding human cationic trypsinogen have been conclusively associated with autosomal dominant hereditary pancreatitis and sporadic nonalcoholic chronic pancreatitis. Most high-penetrance PRSS1 variants increase intrapancreatic trypsin activity by stimulating trypsinogen autoactivation and/or by inhibiting chymotrypsin C-dependent trypsinogen degradation. Alternatively, some PRSS1 variants can cause trypsinogen misfolding, which results in intracellular retention and degradation with consequent endoplasmic reticulum stress. However, not all PRSS1 variants are pathogenic, and clinical relevance of rare variants is often difficult to ascertain. Here we review the PRSS1 variants published since 1996 and discuss their functional properties and role in chronic pancreatitis.

Functional effects of 13 rare PRSS1 variants presumed to cause chronic pancreatitis

OBJECTIVE

Hereditary pancreatitis is caused by mutations in human cationic trypsinogen (PRSS1) which lead to increased autoactivation by altering chymotrypsin C (CTRC)-dependent trypsinogen activation and degradation. Exceptions are some cysteine mutations which cause misfolding, intracellular retention and endoplasmic reticulum stress. Clinical relevance of many PRSS1 variants found in patients with sporadic chronic pancreatitis is unknown but often assumed by analogy with known disease-causing mutations. Functional comparison of PRSS1 variants found in sporadic and hereditary cases is needed to resolve this dilemma.

DESIGN

Here, we investigated the functional phenotype of 13 published PRSS1 variants with respect to autoactivation in the presence of CTRC and cellular secretion.

RESULTS

Only mutation p.D100H increased trypsinogen autoactivation, but this gain in function was offset by a marked reduction in secretion. Five mutants (p.P36R, p.G83E, p.I88N, p.V123M, p.S124F) showed decreased autoactivation due to increased degradation by CTRC. Five mutants exhibited strongly (p.D100H, p.C139F) or moderately (p.K92N, p.S124F, p.G208A) reduced secretion, whereas mutant p.K170E showed slightly increased secretion. Mutant p.I88N was also secreted to higher levels but was rapidly degraded by CTRC. Finally, three mutants (p.Q98K, p.T137M, p.S181G) had no phenotypic alterations relative to wild-type trypsinogen.

CONCLUSIONS

Rare PRSS1 variants found in sporadic chronic pancreatitis do not stimulate autoactivation but may cause increased degradation, impaired secretion or no functional change. Variants with reduced secretion are likely pathogenic due to mutation-induced misfolding and consequent endoplasmic reticulum stress.

Mutational analysis of ATP8B1 in patients with chronic pancreatitis

Background

Mutations in genes encoding cationic trypsinogen (PRSS1), pancreatic secretory trypsin inhibitor (SPINK1) and chymotrypsinogen C (CTRC) are associated with chronic pancreatitis. However, in many patients with a familial chronic pancreatitis pattern suggesting a genetic cause, no mutations in either of these genes can be found, indicating that other, still unknown, associated genes exist. In this respect ATP8B1 is an interesting candidate due to its strong expression in the pancreas, its supposed general function in membrane organization and the higher incidence of pancreatitis in patients with ATP8B1 deficiency.

Methods

We analyzed all 27 ATP8B1 coding exons and adjacent non-coding sequences of 507 chronic pancreatitis patients by direct sequencing. Exons that harbored possible relevant variations were subsequently sequenced in 1,027 healthy controls.

Results

In the exonic regions, 5 novel non-synonymous alterations were detected as well as 14 previously described alterations of which some were associated with ATP8B1 deficiency. However, allele frequencies for any of these variations did not significantly differ between patients and controls. Furthermore, several non-synonymous variants were exclusively detected in control subjects and multiple variants in the non-coding sequence were identified with similar frequencies in both groups.

Conclusions

We did not find an association between heterozygous ATP8B1 variants and chronic pancreatitis in our cohort of patients with hereditary and idiopathic chronic pancreatitis.

Comprehensive screening of chymotrypsin C (CTRC) gene in tropical calcific pancreatitis identifies novel variants

OBJECTIVE

In a previous study, the authors have shown that rather than variants in trypsinogen gene(s), mutations in pancreatic secretory trypsin inhibitor (encoded by SPINK1) and cathepsin B (CTSB) are associated with tropical calcific pancreatitis (TCP). Recently, chymotrypsin C (CTRC) variants that diminish its activity or secretion were found to predict susceptibility to chronic pancreatitis (CP). The authors analysed CTRC variants in a large, ethnically matched case-control TCP cohort.

DESIGN

The authors sequenced all eight exons and flanking regions in CTRC in 584 CP patients (497 TCP, 87 idiopathic CP) and 598 normal subjects and analysed the significance of association using χ(2) test. The authors also investigated interaction of CTRC variants with p.N34S SPINK1 and p.L26V CTSB mutations.

RESULTS

The authors identified 14 variants in CTRC, of which non-synonymous variants were detected in 71/584 CP patients (12.2%) and 22/598 controls (3.7%; OR 3.62, 95% CI 2.21 to 5.93; p=6.2 × 10(-8)). Rather than the commonly reported p.K247_R254del variant in Caucasians, p.V235I was the most common mutation in Indian CP patients (28/575 (4.9%); OR 7.60, 95% CI 2.52 to 25.71; p=1.01 × 10(-5)). Another pathogenic variant, p.A73T was identified in 3.1% (18/584) patients compared with 0.3% (2/598) in controls (OR=9.48, 95% CI 2.19 to 41.03, p=2.5 × 10(-4)). The authors also observed significant association for the synonymous variant c.180C>T (p.(=)) with CP (OR 2.71, 95% CI 1.79 to 4.12, p=5.3 × 10(-7)). Two novel nonsense mutations, p.G242AfsX9 and p.W113X were also identified exclusively in CP patients. No interaction between CTRC variants and p.N34S SPINK1 or p.L26V CTSB mutations was observed.

CONCLUSION

This study on a large cohort of TCP patients provides evidence of allelic heterogeneity and confirms that CTRC variants play a significant role in its pathogenesis.

A conservative assessment of the major genetic causes of idiopathic chronic pancreatitis: data from a comprehensive analysis of PRSS1, SPINK1, CTRC and CFTR genes in 253 young French patients

Idiopathic chronic pancreatitis (ICP) has traditionally been defined as chronic pancreatitis in the absence of any obvious precipitating factors (e.g. alcohol abuse) and family history of the disease. Studies over the past 15 years have revealed that ICP has a highly complex genetic architecture involving multiple gene loci. Here, we have attempted to provide a conservative assessment of the major genetic causes of ICP in a sample of 253 young French ICP patients. For the first time, conventional types of mutation (comprising coding sequence variants and variants at intron/exon boundaries) and gross genomic rearrangements were screened for in all four major pancreatitis genes, PRSS1, SPINK1, CTRC and CFTR. For the purposes of the study, synonymous, intronic and 5'- or 3'-untranslated region variants were excluded from the analysis except where there was persuasive evidence of functional consequences. The remaining sequence variants/genotypes were classified into causative, contributory or neutral categories by consideration of (i) their allele frequencies in patient and normal control populations, (ii) their presumed or experimentally confirmed functional effects, (iii) the relative importance of their associated genes in the pathogenesis of chronic pancreatitis and (iv) gene-gene interactions wherever applicable. Adoption of this strategy allowed us to assess the pathogenic relevance of specific variants/genotypes to their respective carriers to an unprecedented degree. The genetic cause of ICP could be assigned in 23.7% of individuals in the study group. A strong genetic susceptibility factor was also present in an additional 24.5% of cases. Taken together, up to 48.2% of the studied ICP patients were found to display evidence of a genetic basis for their pancreatitis. Whereas these particular proportions may not be extrapolable to all ICP patients, the approach employed should serve as a useful framework for acquiring a better understanding of the role of genetic factors in causing this oligogenic disease.

Characterization of two deletions of the CTRC locus

Novel variants associated with chronic pancreatitis are being increasingly reported. However, most studies have so far only analyzed point mutations and small insertions or deletions. Here we report the characterization of two distinct deletions of the CTRC locus. Variants in four chronic pancreatitis genes, PRSS1, SPINK1, CTRC and CFTR, were systematically analyzed in the studied cases. Copy number change of the CTRC gene was analyzed by quantitative fluorescent multiplex PCR (QFM-PCR). Walking QFM-PCR followed by long-range PCR and direct sequencing were employed to identify the deletion breakpoints at the nucleotide level. A heterozygous CTRC-deleting complex rearrangement, which was co-inherited with different trans variants in SPINK1, CFTR or PRSS1, is associated with variable phenotypes (chronic pancreatitis; pancreatic cancer and chronic pancreatitis; and type 1 diabetes). Moreover, a different homozygous deletion of the CTRC locus was found in an unrelated patient with asymptomatic chronic pancreatitis. Our findings revealed a hitherto unrecognized level of complexity of genotype-phenotype correlation in chronic pancreatitis. The CTRC-deleting complex rearrangement probably resulted from LINE-1-mediated Alu insertion, which represents a novel mutational mechanism causing chronic pancreatitis.

Robust autoactivation, chymotrypsin C independence and diminished secretion define a subset of hereditary pancreatitis-associated cationic trypsinogen mutants

Mutations in human cationic trypsinogen cause hereditary pancreatitis by altering its proteolytic regulation of activation and degradation by chymotrypsin C (CTRC). CTRC stimulates trypsinogen autoactivation by processing the activation peptide to a shorter form, but also promotes degradation by cleaving the calcium-binding loop in trypsinogen. Mutations render trypsinogen resistant to CTRC-mediated degradation and/or increase processing of the activation peptide by CTRC. Here we demonstrate that the activation peptide mutations D19A, D22G, K23R and K23_I24insIDK robustly increased the rate of trypsinogen autoactivation, both in the presence and absence of CTRC. Degradation of the mutants by CTRC was unchanged, and processing of the activation peptide was increased fourfold in the D19A mutant only. Surprisingly, however, this increased processing had only a minimal effect on autoactivation. The tetra-aspartate motif in the trypsinogen activation peptide binds calcium (KD of ~ 1.6 mM), which stimulates autoactivation. Unexpectedly, calcium binding was not compromised by any of the activation peptide mutations. Despite normal binding, autoactivation of mutants D22G and K23_I24insIDK was not stimulated by calcium. Finally, the activation peptide mutants exhibited reduced secretion from transfected cells, and secreted trypsinogen levels were inversely proportional with autoactivation rates. We conclude that D19A, D22G, K23R and K23_I24insIDK form a mechanistically distinct subset of hereditary pancreatitis-associated mutations that exert their effect primarily through direct stimulation of autoactivation, independently of CTRC. The potentially severe clinical impact of the markedly increased autoactivation is offset by diminished secretion, resulting in a clinical phenotype that is indistinguishable from typical hereditary pancreatitis.

In vivo imaging with fluorescent smart probes to assess treatment strategies for acute pancreatitis

BACKGROUND AND AIMS

Endoprotease activation is a key step in acute pancreatitis and early inhibition of these enzymes may protect from organ damage. In vivo models commonly used to evaluate protease inhibitors require animal sacrifice and therefore limit the assessment of dynamic processes. Here, we established a non-invasive fluorescence imaging-based biomarker assay to assess real-time protease inhibition and disease progression in a preclinical model of experimental pancreatitis.

METHODS

Edema development and trypsin activation were imaged in a rat caerulein-injection pancreatitis model. A fluorescent "smart" probe, selectively activated by trypsin, was synthesized by labeling with Cy5.5 of a pegylated poly-L-lysine copolymer. Following injection of the probe, trypsin activation was monitored in the presence or absence of inhibitors by in vivo and ex vivo imaging.

RESULTS

We established the trypsin-selectivity of the fluorescent probe in vitro using a panel of endopeptidases and specific inhibitor. In vivo, the probe accumulated in the liver and a region attributed to the pancreas by necropsy. A dose dependent decrease of total pancreatic fluorescence signal occurred upon administration of known trypsin inhibitors. The fluorescence-based method was a better predictor of trypsin inhibition than pancreatic to body weight ratio.

CONCLUSIONS

We established a fluorescence imaging assay to access trypsin inhibition in real-time in vivo. This method is more sensitive and dynamic than classic tissue sample readouts and could be applied to preclinically optimize trypsin inhibitors towards intrapancreatic target inhibition.

Common genetic variants in the CLDN2 and PRSS1-PRSS2 loci alter risk for alcohol-related and sporadic pancreatitis

Pancreatitis is a complex, progressively destructive inflammatory disorder. Alcohol was long thought to be the primary causative agent, but genetic contributions have been of interest since the discovery that rare PRSS1, CFTR and SPINK1 variants were associated with pancreatitis risk. We now report two associations at genome-wide significance identified and replicated at PRSS1-PRSS2 (P < 1 × 10(-12)) and X-linked CLDN2 (P < 1 × 10(-21)) through a two-stage genome-wide study (stage 1: 676 cases and 4,507 controls; stage 2: 910 cases and 4,170 controls). The PRSS1 variant likely affects disease susceptibility by altering expression of the primary trypsinogen gene. The CLDN2 risk allele is associated with atypical localization of claudin-2 in pancreatic acinar cells. The homozygous (or hemizygous in males) CLDN2 genotype confers the greatest risk, and its alleles interact with alcohol consumption to amplify risk. These results could partially explain the high frequency of alcohol-related pancreatitis in men (male hemizygote frequency is 0.26, whereas female homozygote frequency is 0.07).

Genetics and pathogenesis of chronic pancreatitis: the 2012 update

Chronic pancreatitis is a persistent inflammation of the pancreas that results in irreversible morphological changes and impairment of both exocrine and endocrine functions. Genetic studies of the disease over the past 15 years have led to the identification of four firmly established susceptibility genes namely PRSS1, SPNIK1, CTRC and CFTR. Our previously published review (Chen and Férec. Annu Rev Genomics Hum Genet 2009) has comprehensively summarized the advances made in terms of genetics and pathogenesis of chronic pancreatitis, covering the data available up to early 2009. This review summarizes the important and representative findings published thereafter, focusing on (i) newly found disease-causing mutations, (ii) functional characterization of known variations and (iii) genotype and phenotype relationship.

Strong purifying selection against gene conversions in the trypsin genes of primates

The trypsin gene families of primate species are composed of members who share a remarkable level of sequence similarity. Here, we investigated the gene conversions occurring within the trypsin gene family in five primate species. A total of 36 conversion events, with an average length (±standard deviation) of 1,526 ± 1,124 nucleotides, were detected using two methods. Such extensive gene conversions are likely both the cause and the consequence of the high sequence similarity between primate trypsin genes. In the trypsins encoded by these genes, both the overall amino acid sequences and critical amino acid residues are conserved. Therefore, the numerous long gene conversions we detected between trypsin genes did not alter any of their functionally important amino acid sites. This suggest that, in the trypsin genes of the five primate species studied here, strong purifying selection against gene conversions is occurring in regions containing functionally important residues.

The complex exocrine-endocrine relationship and secondary diabetes in exocrine pancreatic disorders

The pancreas is a dual organ with exocrine and endocrine functions. The interrelationship of the endocrine-exocrine parts of the pancreas is a complex one, but recent clinical and experimental studies have expanded our knowledge. Many disorders primarily of the exocrine pancreas, often solely in the clinical realm of gastroenterologists are associated with diabetes mellitus (DM). Although, the DM becoming disorders are often grouped with type 2 diabetes, the pathogenesis, clinical manifestations and management differ. We review here data on the association of exocrine-endocrine pancreas, the many hormones of the pancreas and their possible effects on the exocrine functions followed by data on the epidemiology, pathogenesis, and management of DM in chronic pancreatitis, cystic fibrosis, pancreatic cancer, and clinical states after pancreatic surgery.

Chymotrypsin C mutations in chronic pancreatitis

Chronic pancreatitis is a persistent inflammatory disorder characterized by destruction of the pancreatic parenchyma, maldigestion, and chronic pain. Mutations in the chymotrypsin C (CTRC) gene encoding the digestive enzyme CTRC have been shown to increase the risk of chronic pancreatitis in European and Asian populations. Here, we review the biochemical properties and physiological functions of human CTRC, summarize the functional defects associated with CTRC mutations, and discuss mechanistic models that might explain the increased disease risk in carriers.

Intragenic duplication: a novel mutational mechanism in hereditary pancreatitis

OBJECTIVES

In a hereditary pancreatitis family from Denmark, we identified a novel intragenic duplication of 9 nucleotides in exon-2 of the human cationic trypsinogen (PRSS1) gene (c.63_71dup) which at the amino-acid level resulted in the insertion of 3 amino acids within the activation peptide of cationic trypsinogen (p.K23_I24insIDK). The aim of the present study was to characterize the effect of this unique genetic alteration on the function of human cationic trypsinogen.

METHODS

Wild-type and mutant cationic trypsinogens were produced recombinantly and purified to homogeneity. Trypsinogen activation was followed by enzymatic assays and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Trypsinogen secretion was measured from transfected HEK 293T cells.

RESULTS

Recombinant cationic trypsinogen carrying the p.K23_I24insIDK mutation exhibited greater than 10-fold increased autoactivation. Activation by human cathepsin B also was accelerated by 10-fold. Secretion of the p.K23_I24insIDK mutant from transfected cells was diminished, consistent with intracellular autoactivation.

CONCLUSIONS

This is the first report of an intragenic duplication within the PRSS1 gene causing hereditary pancreatitis. The accelerated activation of p.K23_I24insIDK by cathepsin B is a unique biochemical property not found in any other pancreatitis-associated trypsinogen mutant. In contrast, the robust autoactivation of the novel mutant confirms the notion that increased autoactivation is a disease-relevant mechanism in hereditary pancreatitis.

Genetic basis of chronic pancreatitis in Asia Pacific region

Chronic pancreatitis (CP) is a disease characterized by irreversible destruction and fibrosis of the parenchyma, leading to pancreatic exocrine insufficiency. In developed countries, the etiology for 60% to 70% of CP amongst male patients is alcohol and 25% are classified as idiopathic chronic pancreatitis (ICP). The genetic predisposition to CP could be an inappropriate activation of trypsinogen in the pancreas. Two common haplotypes, c.101A>G (p.N34S) and c.-215G>A, and four intronic alterations of the serine protease inhibitor Kazal type 1 (SPINK1) gene have been found to increase the risk for CP in the Asia Pacific region. Hence, SPINK1 is thought to be a candidate gene for pancreatitis. A loss-of-function alteration in chymotrypsinogen C (CTRC) gene has been shown to be associated with tropical calcific pancreatitis (TCP). Cathepsin B (CTSB) is also found to be associated with TCP. However mutations in cationic and anionic trypsinogen gene do not play an important role in causing CP in Asia Pacific region.

New PRSS1 and common CFTR mutations in a child with acute recurrent pancreatitis, could be considered an "Hereditary" form of pancreatitis ?

Background

acute recurrent pancreatitis is a complex multigenic disease, the diagnosis is even more difficult when this disease develops in a child.

Case Presentation

a 6-years old boy, hospitalized with epigastric pain radiating to the back showed high serum levels of serum amylase, lipase, CRP and erythrosedimentation rate. Several similar milder episodes of pain, followed by quick recovery and complete disappearance of symptoms were reported during the previous 13 months. The child was medically treated and after 7 days with normal clinic and laboratory tests was discharged with a hypolipidic diet. All the known aetiologic hypotheses were excluded by anamnestic investigation, clinical observation and biochemical evaluation, whereas, anatomic abnormality were excluded by a secretin stimulated magnetic resonance (MRI). At the last follow-up visit, (11 months later), the child showed a normal body weight and anthropometric profile, without further abdominal pain. Mutation screening for coding regions of PRSS1, SPINK1, CFTR and the new hereditary pancreatitis-associated chymotrypsin C (CTRC) genes showed a novel variation, c.541A > G (p.S181G), in the exon 4 of PRSS1 gene and the classical CF p.F508del mutation in the CFTR. Both mutations were present in his clinically normal mother and absent in the patient's father.

Conclusions

this report extend the spectrum of PRSS1 mutations, however, the absence of family history of pancreatitis leaves the present case without the hallmark of the hereditary origin of pancreatitis. At the present knowledge it can be only stated that the combined genotype CFTR (F508del)/PRSS1 (S181G) is associated to a mild phenotype of acute recurrent pancreatitis in this child without any further conclusion on its pathogenetic role or prediction on the course of the disease.

Complete ascertainment of intragenic copy number mutations (CNMs) in the CFTR gene and its implications for CNM formation at other autosomal loci

Over the last 20 years since the discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, more than 1,600 different putatively pathological CFTR mutations have been identified. Until now, however, copy number mutations (CNMs) involving the CFTR gene have not been methodically analyzed, resulting almost certainly in the underascertainment of CFTR gene duplications compared with deletions. Here, high-resolution array comparative genomic hybridization (averaging one interrogating probe every 95 bp) was used to analyze the entire length of the CFTR gene (189 kb) in 233 cystic fibrosis chromosomes lacking conventional mutations. We succeeded in identifying five duplication CNMs that would otherwise have been refractory to analysis. Based upon findings from this and other studies, we propose that deletion and duplication CNMs in the human autosomal genome are likely to be generated in the proportion of approximately 2-3:1. We further postulate that intragenic gene duplication CNMs in other disease loci may have been routinely underascertained. Finally, our analysis of +/-20 bp flanking each of the 40 CFTR breakpoints characterized at the DNA sequence level provide support for the emerging concept that non-B DNA conformations in combination with specific sequence motifs predispose to both recurring and nonrecurring genomic rearrangements.

Sequence analysis of the human tyrosylprotein sulfotransferase-2 gene in subjects with chronic pancreatitis

BACKGROUND/AIMS

Human trypsinogens are post-translationally sulfated on Tyr154 by the Golgi resident enzyme tyrosylprotein sulfotransferase-2 (TPST2). Tyrosine sulfation stimulates the autoactivation of human cationic trypsinogen. Because increased trypsinogen autoactivation has been implicated as a pathogenic mechanism in chronic pancreatitis, we hypothesized that genetic variants of TPST2 might alter the risk for the disease.

METHODS

We sequenced the 4 protein-coding exons and the adjacent intronic sequences of TPST2 in 151 subjects with chronic pancreatitis and in 169 healthy controls. The functional effect of TPST2 variants on trypsinogen sulfation was analyzed in transfected HEK 293T cells.

RESULTS

We detected 10 common polymorphic variants, including 6 synonymous variants and 4 intronic variants, with similar frequencies in patients and controls. None of the 8 common haplotypes reconstructed from the frequent variants showed an association with chronic pancreatitis. In addition, we identified 5 rare TPST2 variants, which included 3 synonymous alterations, the c.458G>A (p.R153H) nonsynonymous variant and the c.-9C>T variant in the 5' untranslated region. The p.R153H variant was found in a family with hereditary pancreatitis; however, it did not segregate with the disease. In functional assays, both the p.R153H and c.-9C>T TPST2 variants catalyzed trypsinogen sulfation as well as wild-type TPST2.

CONCLUSION

Genetic variants of human TPST2 exert no influence on the risk of chronic pancreatitis.

Genetic aspects of pancreatitis

Acute pancreatitis and chronic pancreatitis are complex inflammatory disorders of the pancreas with unpredictable severity, complications, and clinical courses. Growing evidence for genetic risk and modifying factors, plus strong evidence that only a minority of patients with these disorders are heavy alcohol drinkers, has revolutionized our concept of these diseases. Once considered a self-inflicted injury, pancreatitis is now recognized as a complex inflammatory condition like inflammatory bowel disease. Genetic linkage and candidate gene studies have identified six pancreas-targeting factors that are associated with changes in susceptibility to acute and/or chronic pancreatitis, including cationic trypsinogen (PRSS1), anionic trypsinogen (PRSS2), serine protease inhibitor Kazal 1 (SPINK1), cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsinogen C (CTRC) and calcium-sensing receptor (CASR). Patients with mutations in these genes are at increased risk of pancreatitis caused by a variety of stresses including hyperlipidemia and hypercalcemia. Multiple studies are reporting new polymorphisms, as well as complex gene x gene and gene x environmental interactions.

Genetic analysis of the glycoprotein 2 gene in patients with chronic pancreatitis

OBJECTIVES

The aim of this study was to evaluate whether variations in the glycoprotein 2 gene (GP2) may potentially affect the risk of chronic pancreatitis.

METHODS

Six hundred sixty-one French white patients (idiopathic chronic pancreatitis, n = 590; familial chronic pancreatitis, n = 42; hereditary pancreatitis, n = 29), 445 Dravidian patients from India (tropical calcific pancreatitis, n = 306; idiopathic chronic pancreatitis, n = 139), and 962 unrelated healthy subjects (French white, n = 500; Dravidian, n = 462) participated in this case-control association study. The entire coding sequence of the GP2 gene was searched for conventional genetic variations by direct sequencing, whereas all 12 exons of the GP2 gene were screened for copy number variations by quantitative fluorescent multiplex-polymerase chain reaction.

RESULTS

Only 3 rare missense mutations (p.A137T, p.E250D, and p.V432M; only p.E250D was not detected in any control subjects) and 3 common synonymous polymorphisms (c.348C>T, c.714G>C, and c.1275A>G) were identified. The c.348C>T and c.1275A>G variations were found to be contradictorily associated with the disease (ranging from protective effects to disease-predisposing effects) in the French white and Indian populations.

CONCLUSION

The paucity of patient-specific missense mutations and contradictory findings with respect to 2 common polymorphisms in the 2 contrasting populations suggest that the GP2 gene is unlikely to play a major role in the etiology of chronic pancreatitis.

The c.1275A>G putative chronic pancreatitis-associated synonymous polymorphism in the glycoprotein 2 (GP2) gene decreases exon 9 inclusion

We have recently found that a common synonymous single nucleotide polymorphism (SNP), c.1275A>G, in exon 9 of the glycoprotein 2 (GP2) gene was significantly underrepresented in French idiopathic chronic pancreatitis patients 20years old or younger at disease onset than in the control population. To further investigate to this preliminary genetic finding, we characterized the functionality of c.1275A>G in the context of a minigene system. Bioinformatics analysis predicted that c.1275A>G could lead to disruption/generation of exonic splicing enhancer hexamers within exon 9 of the GP2 gene. Minigene analysis revealed that both the wild-type and mutant sequences expressed a full-length transcript and a short transcript lacking exon 9. Quantitation of the relative amount of the two transcripts indicated that the fraction of the full-length transcript derived from c.1275A>G is much lower than that derived from the wild-type (51.9% vs 77.4%). Extinction of two splicing factors (SF2/ASF and SC35) by RNA interference also affected c.1275A>G more seriously than the wild-type in terms of exon 9 skipping. Exon 9 skipping was presumed to cause a loss of GP2 function. This study represents the first detailed analysis of any variation in the GP2 gene and gives some support to the putative association of c.1275A>G with disease protection.

Prevalence of pancreatic diabetes in patients carrying mutations or polymorphisms of the PRSS1 gene in the Han population

OBJECTIVE

This study updated the estimated prevalence of type 3c diabetes damage to the pancreas through different genotypes of PRSS1 and their clinical characteristics in the Han population.

SUBJECTS AND METHODS

Cross-sectional analysis was performed of the most recent (2003-2007) patients with pancreatitis from six hospitals of the Han population in South China (n = 253).

RESULTS

There were 32 patients with pancreatitis carrying a PRSS1 gene abnormality within intron region among 253 cases of pancreatitis, including 27 patients carrying novel single nucleotide polymorphisms, namely, IVS 3 +75 A --> G conversion, and five patients with the mutation IVS3 + 10 T --> G. Among these patients, there were only three cases of patients with diabetes (9.37%). This was lower than the prevalence of abnormalities in the exons of the PRSS1 gene (51.92%): 12 patients with c.361 G --> A, eight patients with c.415 T --> A, and five patients with c.365G --> A. Among them were 12 persons with diabetes, including five requiring insulin to regulate blood sugar. What is more, among the 27 patients carrying PRSS1 gene polymorphism (c.486 C --> T, within the exon 4), there were 15 persons with diabetes symptoms. More than 40% of these patients required insulin to regulate blood sugar.

CONCLUSIONS

An abnormality within the intron region of the PRSS1 gene represents one of the causes of pancreatitis in Chinese patients, but it is not related to pancreatic diabetes. However, the exon abnormality obviously raises the morbidity rate of type 3c diabetes, which relies on insulin.

Tropical calcific pancreatitis and its association with CTRC and SPINK1 (p.N34S) variants

BACKGROUND

Tropical calcific pancreatitis (TCP) is a relatively common form of chronic pancreatitis in parts of Asia and Africa. The SPINK1 variant p.N34S is strongly associated with TCP, but other genetic factors remain to be defined. Chymotrypsinogen C (CTRC) degrades trypsinogen and loss-of-function variants have been found in European patients with chronic pancreatitis. Preliminary data indicate that CTRC might increase the risk for TCP.

MATERIALS AND METHODS

We selected 150 Indian TCP patients and 150 Indian controls to perform mutational screening of the complete coding region of CTRC and exon 3 of SPINK1. We performed in-silico analysis and functional studies of novel CTRC variants.

RESULTS

We identified eight variants among this sample. Three were synonymous and c.180 C>T was significantly enriched in patients (odds ratio=2.09; 95% confidence interval=1.19-3.67; P=0.03). We identified a novel nonsynonymous CTRC (p.G61R) variant in one of 146 patients (0.7%), but absent from controls. In-silico analysis showed that this variant affected a conserved residue, and functional analysis showed that p.G61R results in a complete loss of CTRC secretion from transiently transfected human embryonic kidney 293T cells. SPINK1 p.N34S was present in 31.8% of patients compared with 4.7% in controls, there was no significant cosegregation with CTRC variants.

CONCLUSION

The contribution of CTRC variants to TCP is relatively small, but the identification of novel loss-of-function variants (p.G61R) underscores the importance of the trypsinogen pathway in causing TCP.

Hereditary pancreatitis caused by mutation-induced misfolding of human cationic trypsinogen: a novel disease mechanism

We investigated the biochemical properties and cellular expression of the c.346C>T (p.R116C) human cationic trypsinogen (PRSS1) mutant, which we identified in a German family with autosomal dominant hereditary pancreatitis. This mutation leads to an unpaired Cys residue with the potential to interfere with protein folding via incorrect disulfide bond formation. Recombinantly expressed p.R116C trypsinogen exhibited a tendency for misfolding in vitro. Biochemical analysis of the correctly folded, purified p.R116C mutant revealed unchanged activation and degradation characteristics compared to wild type trypsinogen. Secretion of mutant p.R116C from transfected 293T cells was reduced to approximately 20% of wild type. A similar secretion defect was observed with another rare PRSS1 variant, p.C139S, whereas mutants p.A16V, p.N29I, p.N29T, p.E79K, p.R122C, and p.R122H were secreted normally. All mutants were detected in cell extracts at comparable levels but a large portion of mutant p.R116C was present in an insoluble, protease-sensitive form. Consistent with intracellular retention of misfolded trypsinogen, the endoplasmic reticulum (ER) stress markers immunoglobulin-binding protein (BiP) and the spliced form of the X-box binding protein-1 (XBP1s) were elevated in cells expressing mutant p.R116C. The results indicate that mutation-induced misfolding and intracellular retention of human cationic trypsinogen causes hereditary pancreatitis in carriers of the p.R116C mutation. ER stress triggered by trypsinogen misfolding represents a new potential disease mechanism for chronic pancreatitis.

Human genes involved in copy number variation: mechanisms of origin, functional effects and implications for disease

Copy number variants (CNVs) overlap over 7000 genes, many of which are pivotal in biological pathways. The implications of this are profound, with consequences for evolutionary studies, population genetics, gene function and human phenotype, including elucidation of genetic susceptibility to major common diseases, the heritability of which has thus far defied full explanation. Even though this research is still in its infancy, CNVs have already been associated with a number of monogenic, syndromic and complex diseases: the development of high throughput and high resolution techniques for CNV screening is likely to bring further new insights into the contribution of copy number variation to common diseases. Amongst genes overlapped by CNVs, significant enrichments for certain gene ontology categories have been identified, including those related to immune responses and interactions with the environment. Genes in both of these categories are thought to be important in evolutionary adaptation and to be particular targets of natural selection. Thus, a full appreciation of copy number variation may be important for our understanding of human evolution.

Genetic mechanisms underlying the pathogenesis of tropical calcific pancreatitis

Chronic pancreatitis is known to be a heterogeneous disease with varied etiologies. Tropical calcific pancreatitis (TCP) is a severe form of chronic pancreatitis unique to developing countries. With growing evidence of genetic factors contributing to the pathogenesis of TCP, this review is aimed at compiling the available information in this field. We also propose a two hit model to explain the sequence of events in the pathogenesis of TCP.

Chronic pancreatitis: genetics and pathogenesis

Chronic pancreatitis (CP) is a persistent inflammation of the pancreas. Over the past 12 years, genetic studies of hereditary, familial, and idiopathic forms of CP have made great progress in defining the disease pathogenesis. Identification of gain-of-function missense and copy number mutations in the cationic trypsinogen gene (PRSS1) and loss-of-function variants in both the pancreatic secretory trypsin inhibitor (SPINK1) and chymotrypsinogen C (CTRC) genes has firmly established the pivotal role of prematurely activated trypsin within the pancreas in the etiology of CP. Loss-of-function variants in the cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-sensing receptor (CASR) genes also increase the risk of CP. Here, we review recent developments in this rapidly evolving field, highlight the importance of gene-gene and gene-environment interactions in causing the disease, and discuss the opportunities and challenges in identifying novel genetic factors that affect susceptibility/resistance to CP.

Molecular basis for pancreatitis

PURPOSE OF REVIEW

This timely review will focus on clinical and basic science studies that have greatly advanced our knowledge of the molecular mechanisms of both acute pancreatitis and chronic pancreatitis over the last year.

RECENT FINDINGS

Animal models of both severe acute pancreatitis and chronic pancreatitis have recently been developed. Several unexpected protective mechanisms, mediated by the protease activated receptor 2 and heat shock protein 70, have been described. A genetic study suggested that polymorphisms in toll-like receptor-4 might affect the risk of developing infections in acute pancreatitis. Studies of chronic pancreatitis have shown that specific neural receptors, transient receptor potential vanilloid subtype 1, mediate pain responses in a model of chronic pancreatitis. The pancreatic zymogen, chymotrypsin C, can degrade pathologically activated trypsin in the acinar cell. Inactivating mutations in chymotrypsin C have been reported to predispose to the development of chronic pancreatitis, especially in those who are prone to alcohol abuse.

SUMMARY

The implications of the last year's findings are widespread. Improved animal models of acute pancreatitis and chronic pancreatitis will be critical for performing pilot studies of therapy. A greater understanding of genetic factors and pain responses could lead to potential treatments. This review will first discuss issues related to acute pancreatitis, and then conclude with studies most relevant to chronic disease.