Association of rare SPINK1 gene mutation with another base substitution in chronic pancreatitis patients

Meta-analysis of the impact of the SPINK1 c.194 + 2T > C variant in chronic pancreatitis

BACKGROUND AND AIMS

The SPINK1 c.194 + 2T > C variant has been increasingly recognized as an important risk factor for chronic pancreatitis (CP). However, there is no clear agreement on its contribution to different ethnicities and CP etiologies. To address this issue, a meta-analysis of literature was performed.

METHODS

Studies addressing the presence of the SPINK1 c.194 + 2T > C variant in CP patients and controls were retrieved from the PubMed, EMBASE and Cochrane databases. Initial analysis included all CP patients, followed by subgroup analyses for East Asian and non-East Asian patients, and for idiopathic CP (ICP) and non-ICP.

RESULTS

A total of 13 studies were retrieved for analysis, comprising 2097 cases and 4019 controls. There were 126 cases (10.01%) carrying the SPINK1 c.194 + 2T > C variant in cases, while only two controls were carriers (0.05%). Overall, the variant was significantly associated with an increased risk of CP (OR = 25.73). In the subgroup, the variant was significantly associated with increased risk of CP in East Asians (OR = 73.16), and in non-East Asians (OR = 10.21). Further, the contribution of the variant in ICP (OR = 35.31) was found to be higher than in non-ICP (25.75).

CONCLUSIONS

The SPINK1 c.194 + 2T > C variant is a strong risk factor for CP, especially in East Asian patients with ICP.

Frequency of Tabagism and N34S and P55S Mutations of Serine Peptidase Inhibitor, Kazal Type 1 (SPINK1) and R254W Mutation of Chymotrypsin C (CTRC) in Patients With Chronic Pancreatitis and Controls

OBJECTIVE

This study aimed to investigate the association between chronic pancreatitis and smoking or genetic mutations.

METHODS

The study sample comprised 148 patients with chronic pancreatitis, 110 chronic alcoholic subjects without pancreatic disease, and 297 volunteer blood donors.

RESULTS

Of the patients with chronic pancreatitis, 74% had alcoholic etiology and 26% had idiopathic pancreatitis. The frequency of smoking was 91.4% in patients with alcoholic pancreatitis, higher than 73.3% in alcoholic subjects without pancreatitis (P < 0.01). The difference in smoking frequency was not significant between the patients with idiopathic pancreatitis and blood donors. The N34S mutation of serine peptidase inhibitor, Kazal type 1 (SPINK1) was found in 2.7% of patients with chronic alcoholic pancreatitis, in 5.3% of patients with idiopathic pancreatitis, and in 0.4% of blood donors (P = 0.02). The P55S mutation of SPINK1 was found in 2.7% of patients with alcoholic pancreatitis and in 0.7% of blood donors (P = 0.12). The R254W mutation of chymotrypsin C was found in 0.9% of patients with alcoholic pancreatitis, in 0.9% of chronic alcoholic subjects without pancreatitis, and in 0.4% of blood donors (P = 0.75). In all cases, the mutations were heterozygous.

CONCLUSIONS

Smoking and the N34S mutation of SPINK1 were positively correlated with chronic pancreatitis.

Functional significance of SPINK1 promoter variants in chronic pancreatitis

Chronic pancreatitis is a progressive inflammatory disorder of the pancreas, which often develops as a result of genetic predisposition. Some of the most frequently identified risk factors affect the serine protease inhibitor Kazal type 1 (SPINK1) gene, which encodes a trypsin inhibitor responsible for protecting the pancreas from premature trypsinogen activation. Recent genetic and functional studies indicated that promoter variants in the SPINK1 gene might contribute to disease risk in carriers. Here, we investigated the functional effects of 17 SPINK1 promoter variants using luciferase reporter gene expression assay in four different cell lines, including three pancreatic acinar cell lines (rat AR42J with or without dexamethasone-induced differentiation and mouse 266-6) and human embryonic kidney 293T cells. We found that most variants caused relatively small changes in promoter activity. Surprisingly, however, we observed significant variations in the effects of the promoter variants in the different cell lines. Only four variants exhibited consistently reduced promoter activity in all acinar cell lines, confirming previous reports that variants c.-108G>T, c.-142T>C, and c.-147A>G are risk factors for chronic pancreatitis and identifying c.-52G>T as a novel risk variant. In contrast, variant c.-215G>A, which is linked with the disease-associated splice-site mutation c.194 + 2T>C, caused increased promoter activity, which may mitigate the overall effect of the pathogenic haplotype. Our study lends further support to the notion that sequence evaluation of the SPINK1 promoter region in patients with chronic pancreatitis is justified as part of the etiological investigation.

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.

CFTR, SPINK1, PRSS1, and CTRC mutations are not associated with pancreatic cancer in German patients

OBJECTIVE

Mutations in the cationic trypsinogen (PRSS1), cystic fibrosis transmembrane conductance regulator (CFTR), serine protease inhibitor Kazal type 1 (SPINK1), and chymotrypsin C (CTRC) genes are associated with an elevated risk for chronic pancreatitis, which is a known risk factor for pancreatic cancer (PC). Therefore, we analyzed whether PRSS1, CFTR, SPINK1, and/or CTRC mutations are associated with pancreatic adenocarcinoma.

METHODS

The study cohort was composed of 121 PC patients, of whom 74 were classified as having chronic pancreatitis, 102 patients with idiopathic chronic pancreatitis, and 130 as healthy controls. Mutation analyses for the CFTR, SPINK1, PRSS1, and CTRC genes were performed for the presence of the most common mutations.

RESULTS

The frequency of CFTR mutations in patients with PC was not significantly different in comparison with healthy controls and controls with pancreatitis. The SPINK1 mutation frequency was significantly decreased in patients with PC in comparison with patients with idiopathic pancreatitis but varied not significantly in comparison with healthy controls. None of the selected 121 PC samples showed a pancreatitis-predisposing mutation in the PRSS1 or CTRC gene.

CONCLUSIONS

Mutations in the genes CFTR, SPINK1, PRSS1, and CTRC do not seem to significantly increase the risk for pancreatic adenocarcinoma.

Mechanisms of CFTR functional variants that impair regulated bicarbonate permeation and increase risk for pancreatitis but not for cystic fibrosis

CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev) cause complete loss of CFTR function and result in cystic fibrosis (CF), a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize that those CFTR mutations that disrupt the WNK1-SPAK activation mechanisms cause a selective, bicarbonate defect in channel function (CFTRBD) affecting organs that utilize CFTR for bicarbonate secretion (e.g. the pancreas, nasal sinus, vas deferens) but do not cause typical CF. To understand the structural and functional requirements of the CFTR bicarbonate-preferring channel, we (a) screened 984 well-phenotyped pancreatitis cases for candidate CFTRBD mutations from among 81 previously described CFTR variants; (b) conducted electrophysiology studies on clones of variants found in pancreatitis but not CF; (c) computationally constructed a new, complete structural model of CFTR for molecular dynamics simulation of wild-type and mutant variants; and (d) tested the newly defined CFTRBD variants for disease in non-pancreas organs utilizing CFTR for bicarbonate secretion. Nine variants (CFTR R74Q, R75Q, R117H, R170H, L967S, L997F, D1152H, S1235R, and D1270N) not associated with typical CF were associated with pancreatitis (OR 1.5, p = 0.002). Clones expressed in HEK 293T cells had normal chloride but not bicarbonate permeability and conductance with WNK1-SPAK activation. Molecular dynamics simulations suggest physical restriction of the CFTR channel and altered dynamic channel regulation. Comparing pancreatitis patients and controls, CFTRBD increased risk for rhinosinusitis (OR 2.3, p<0.005) and male infertility (OR 395, p<<0.0001). WNK1-SPAK pathway-activated increases in CFTR bicarbonate permeability are altered by CFTRBD variants through multiple mechanisms. CFTRBD variants are associated with clinically significant disorders of the pancreas, sinuses, and male reproductive system.

Comprehensive screening for PRSS1, SPINK1, CFTR, CTRC and CLDN2 gene mutations in Chinese paediatric patients with idiopathic chronic pancreatitis: a cohort study

OBJECTIVE

Genetic alterations may contribute to chronic pancreatitis (CP) in Chinese young patients. This study was designed to investigate mutations of cationic trypsinogen (PRSS1), pancreatic secretory trypsin inhibitor or serine protease inhibitor Kazal type 1 (SPINK1), cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsin C (CTRC) and CLDN2 genes and the copy number variations (CNVs) of PRSS1 and asses associations with the development of idiopathic CP (ICP) in Chinese children.

DESIGN

Retrospective.

SETTING

A single center.

PARTICIPANTS

75 ICP Chinese children (40 boys and 35 girls).

PRIMARY AND SECONDARY OUTCOME MEASURES

Mutations of PRSS1, SPINK1, CFTR, CTRC and CLDN2 genes and CNVs.

RESULTS

7 patients had heterozygous mutations in PRSS1, that is, N29I (n=1), R122H or R122C (n=6). The CNVs of PRSS1 in five patients had abnormal copies (1 copy (n=4), five copies (n=1)). 43 patients had IVS3+2T>C (rs148954387) (10 homozygous and 33 heterozygous) in SPINK1. None of the PRSS1 mutation patients carried a SPINK1 mutation. Frequency of PRSS1 and SPINK1 mutations was 9.3% and 57.3%, respectively, with an overall frequency of 66.6% (50/75). In addition, one patient had a novel deletion of CFTR (GCTTCCTA from c.500 to c.508 leading to the shortened polypeptide molecule via a stop codon). Another patient had a novel missense in CLDN2 exon 2 (c.592A>C mutation). Clinically, patients with SPINK1 mutations had a higher rate of pancreatic duct stones, pancreatic pseudocyst and pancreatic calcification than those without SPINK1 mutations (p<0.05).

CONCLUSIONS

SPINK1 mutations were more commonly associated with Chinese children with ICP. SPINK1 IVS3+2T>C mutation may play an important role in the pathogenesis of Chinese paediatric ICP. However, further study is needed to confirm and to investigate the role of these genes in the development of Chinese ICP.

The contribution of the SPINK1 c.194+2T>C mutation to the clinical course of idiopathic chronic pancreatitis in Chinese patients

BACKGROUND

Recent data suggest that the serine protease inhibitor Kazal type 1 (SPINK1) gene mutation is associated with idiopathic chronic pancreatitis. However, few studies have focused on the serine protease inhibitor Kazal type 1 c.194+2T>C mutation. Therefore, our goal was to study the prevalence and impact of serine protease inhibitor Kazal type 1 mutations on the clinical profile of idiopathic chronic pancreatitis patients in China.

METHODS

A retrospective-cohort study of 118 Chinese patients with idiopathic chronic pancreatitis was performed, and genetic tests were carried out to detect SPINK1 mutations. Subjects without pancreatitis were used as controls. In total, 118 idiopathic chronic pancreatitis patients and 100 control subjects were evaluated.

RESULTS

The serine protease inhibitor Kazal type 1 c.194+2T>C variant was present in 44.9% of patients with idiopathic chronic pancreatitis. The frequency of diabetes in idiopathic chronic pancreatitis patients with the serine protease inhibitor Kazal type 1 c.194+2T>C mutation (39.6%) was higher than that of patients without the mutation (9.2%). The time to occurrence of diabetes mellitus after idiopathic chronic pancreatitis symptom onset is significantly influenced by the c.194+2T>C mutation (p<0.001). In addition, the mean age of diabetes onset in patients with the serine protease inhibitor Kazal type 1 c.194+2T>C mutation (38.33 ± 9.50) was significantly younger than that of patients without this mutation (49.67 ± 6.74).

CONCLUSIONS

The presence of the serine protease inhibitor Kazal type 1 c.194+2T>C mutation seems to be associated with idiopathic chronic pancreatitis and could predispose individuals to pancreatic diabetes onset at an earlier age.

Minigene analysis of intronic variants in common SPINK1 haplotypes associated with chronic pancreatitis

BACKGROUND AND AIMS

Two common haplotypes of the serine protease inhibitor Kazal type 1 (SPINK1) gene have been shown to increase the risk for chronic pancreatitis. A haplotype comprising the c.101A>G (p.N34S) missense variant and four intronic alterations has been found worldwide, whereas a second haplotype consisting of the c.-215G>A promoter variant and the c.194+2T>C intronic alteration has been observed frequently in Japan.

METHODS

In the present study, the functional significance of the intronic variants in the pathogenic SPINK1 haplotypes was examined by utilising minigenes, which harbour individual introns placed in the appropriate context of the full-length SPINK1 cDNA. Cells transfected with the SPINK1 minigenes secrete active trypsin inhibitor, thereby allowing evaluation of mutational effects simultaneously on transcription, splicing, translation and secretion.

RESULTS

It was found that the c.194+2T>C intronic alteration abolished SPINK1 expression at the mRNA level, with consequent loss of inhibitor secretion, whereas the p.N34S-associated intronic variants had no detectable functional effect.

CONCLUSIONS

Taken together with previous studies, the results indicate that all known variants within the p.N34S-associated haplotype are functionally innocuous, suggesting that an as yet unidentified variant within this haplotype is responsible for the pathogenic effect. The marked negative impact of the c.194+2T>C variant on SPINK1 expression supports the notion that SPINK1 variants increase the risk of chronic pancreatitis by diminishing protective trypsin inhibitor levels.

N34S mutation in the SPINK1 gene is not associated with alternative splicing

OBJECTIVES

Previous studies have shown an association between chronic pancreatitis (CP) and mutations, especially the N34S mutation, in the serine protease inhibitor Kazal type 1 (SPINK1) gene. But the underlying molecular mechanisms are unknown. The aberrant splicing caused by the cosegregating intronic mutations might play a role, but this hypothesis has not been tested. We here examined the messenger RNA sequences of the SPINK1 gene in patients carrying the mutations.

METHODS

RNA was isolated from the surgically resected pancreas of 2 CP patients carrying the homozygous N34S mutation and from the gastric biopsy specimen of a CP patient carrying the heterozygous [-215G>A; IVS3+2T>C] mutation. The entire coding region of the SPINK1 gene was amplified by reverse transcription-polymerase chain reaction, subcloned, and sequenced. The level of the wild-type SPINK1 transcript was assessed by real-time polymerase chain reaction.

RESULTS

Alternative splicing was not associated with the N34S mutation. On the other hand, the [-215G>A; IVS3+2T>C] mutation caused skipping of whole exon 3, where the trypsin binding site is located. This mutated protein was predicted to consist of 63 amino acids: deletion of amino acid sequence from residues 30 to 64 and shifting of reading frame at amino acid 65 with a novel stop codon. The expression of the wild-type SPINK1 transcript was decreased to 62% of the healthy control in the CP patient carrying the heterozygous [-215G>A; IVS3+2T>C] mutation.

CONCLUSIONS

Splicing mutation might represent a mechanism for SPINK1-associated CP, but the N34S mutation is not associated with alternative splicing.