Autosomal Dominant Hereditary Pancreatitis Research Articles

A novel p.Ser282Pro CPA1 variant is associated with autosomal dominant hereditary pancreatitis

We read with great interest the recent publication by Nemeth et al .1 in which the authors demonstrate that a misfolding human cationic trypsinogen (serine protease 1, PRSS1) variant causes autosomal dominant hereditary chronic pancreatitis (CP) by inducing endoplasmic reticulum (ER) stress. Previously, the same mechanism was proposed for carboxypeptidase A1 ( CPA1 ) gene variants strongly associated with early onset sporadic CP;2 however, the association of misfolding CPA1 variants with familial or hereditary CP has not been demonstrated so far. Here, we report two Polish families with hereditary CP carrying a novel heterozygous c.844T>C (p.Ser282Pro) CPA1 variant. In Family 1, the index patient, her mother and uncle (half-brother of the mother) developed CP (figure 1). The age of diagnosis was 17 years for the index patient and 51 and 31 years (with earlier abdominal pain) for the mother and the uncle, respectively. In Family 2, three members were affected by CP (figure 1): the index patient, her mother and her father with ages of onset of 12, 32 and 34 years, respectively. In both families, the diagnosis of CP was confirmed by …

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.

Increased Activation of Hereditary Pancreatitis-associated Human Cationic Trypsinogen Mutants in Presence of Chymotrypsin C

Mutations in human cationic trypsinogen (PRSS1) cause autosomal dominant hereditary pancreatitis. Increased intrapancreatic autoactivation of trypsinogen mutants has been hypothesized to initiate the disease. Autoactivation of cationic trypsinogen is proteolytically regulated by chymotrypsin C (CTRC), which mitigates the development of trypsin activity by promoting degradation of both trypsinogen and trypsin. Paradoxically, CTRC also increases the rate of autoactivation by processing the trypsinogen activation peptide to a shorter form. The aim of this study was to investigate the effect of CTRC on the autoactivation of clinically relevant trypsinogen mutants. We found that in the presence of CTRC, trypsinogen mutants associated with classic hereditary pancreatitis (N29I, N29T, V39A, R122C, and R122H) autoactivated at increased rates and reached markedly higher active trypsin levels compared with wild-type cationic trypsinogen. The A16V mutant, known for its variable disease penetrance, exhibited a smaller increase in autoactivation. The mechanistic basis of increased activation was mutation-specific and involved resistance to degradation (N29I, N29T, V39A, R122C, and R122H) and/or increased N-terminal processing by CTRC (A16V and N29I). These observations indicate that hereditary pancreatitis is caused by CTRC-dependent dysregulation of cationic trypsinogen autoactivation, which results in elevated trypsin levels in the pancreas.

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.

Trypsinogen Copy Number Mutations in Patients With Idiopathic Chronic Pancreatitis

We have recently reported that the triplication of a approximately 605 kilobase segment containing the PRSS1 (encoding cationic trypsinogen) and PRSS2 (encoding anionic trypsinogen) genes causes hereditary pancreatitis. Here we went further to investigate whether this copy number mutation could account for some unidentified French white patients with idiopathic chronic pancreatitis (ICP) or familial chronic pancreatitis (FCP) as well as Indian patients with tropical calcific pancreatitis (TCP). Patients and controls were screened by means of previously described quantitative fluorescent multiplex polymerase chain reaction and/or genotyping of the microsatellite marker rs3222967. The approximately 605 kilobase triplication and a novel duplication (confirmed by fluorescence in situ hybridization) of the trypsinogen locus were detected in 10 and 2 of 202 ICP patients, respectively (age of disease onset, <or=20 years) but were absent in 282 French controls. In addition, the duplication mutation was found in 2 of 1044 ICP patients whose age of disease onset was >20 years. However, the 2 trypsinogen copy number mutations were observed in neither 103 FCP patients nor 268 Indian TCP patients. Our findings revealed the molecular basis of 6% of the young ICP patients and further demonstrated that chronic pancreatitis is a genomic disorder. Our findings also add to the mounting evidence showing that trypsinogen gene mutations do not appear to play an important role in the pathogenesis of TCP in the Indian population. Finally, a dividend of this study is that we have provided convincing evidence to show that all 5 previously described copy number variations involving PRSS1 or/and PRSS2 are artifacts.

Signal peptide variants that impair secretion of pancreatic secretory trypsin inhibitor (SPINK1) cause autosomal dominant hereditary pancreatitis

Variants of the SPINK1 gene encoding pancreatic secretory trypsin inhibitor have been described in association with chronic pancreatitis (CP). These alterations are believed to cause a loss of function by either impairing the trypsin inhibitory activity or reducing expression. Here we report two novel SPINK1 variants in exon 1 that affect the secretory signal peptide. The disease-associated c.41T>G (p.L14R) alteration was found in two European families with autosomal dominant hereditary pancreatitis, whereas the c.36G>C (p.L12F) variant was identified as a frequent alteration in subjects of African descent. The functional effects of both alterations and the previously reported c.41T>C (p.L14P) variant were characterized by activity assays and Western blots of wild-type and mutant SPINK1 expressed in human embryonic kidney 293T and Chinese hamster ovary cells. Alterations p.L14R and p.L14P destined the inhibitor for rapid intracellular degradation and thereby abolished SPINK1 secretion, whereas the p.L12F variant showed no detrimental effect. The results provide the first clear experimental demonstration that alterations that markedly reduce SPINK1 expression are associated with classic hereditary pancreatitis. Therefore, these variants should be classified as severe and regarded as disease-causing rather than disease-modifiers.

Pancreatitis in fibrocalculous pancreatic diabetes mellitus is not associated with common mutations in the trypsinogen gene

A distinct type of pancreatitis associated with diabetes, termed fibrocalculous pancreatic diabetes (FCPD), has been reported in tropical developing countries including Bangladesh. The molecular basis for autosomal dominant hereditary pancreatitis (HP) has recently been attributed to mutations in exons 2 and 3 of the trypsinogen gene. We have investigated the hypothesis that mutations in the aforementioned exons of this gene might also predispose to FCPD. Seventy Bangladeshi and 50 South Indian unrelated FCPD patients and seven South Indian families with FCPD probands were studied. Pancreatic calcification was confirmed by abdominal X-ray, ultrasound and/or ERCP. Established mutations of exons 2 and 3 of the trypsinogen gene were studied in these subjects by PCR-RFLP analysis and DNA sequencing. The mutations found in hereditary pancreatitis were not observed in this collection of FCPD subjects, and complete DNA sequencing of exons 2 and 3 of the fourth cationic trypsinogen gene also excluded any new mutations. These results indicate that chronic pancreatitis of FCPD is unlikely to be caused by common mutations in the trypsinogen gene.

Linkage Studies in a Large Kindred with Hereditary Pancreatitis Confirms Mapping of the Gene to a 16-cM Region on 7q

We report localization of the gene for autosomal dominant hereditary pancreatitis (HP) to a small region of the long arm of chromosome 7 in a large four-generation kindred. Affected family members may first become symptomatic in childhood or even infancy with progression to pancreatic calcification, pseudocyst formation, endocrine and exocrine insufficiency, and even pancreatic cancer in some cases. However, obligate gene carriers may remain virtually symptom free throughout life. HP is the most common cause of childhood pancreatitis in the United States. Gene mapping with microsatellite markers demonstrates that HP is tightly linked to the marker D7S684 (Zmax= 7.0, θ = 0.0). Three obligate recombinants place the HP locus within a 16-cM interval between markers D7S495 and D7S688. This confirms the localization of HP to 7q reported in a separate French kindred (2).