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It has long been known that canonical 5′ splice site (5′SS) GT>GC variants may be compatible with normal splicing. However, to date, the actual scale of canonical 5′SSs capable of generating wild‐type transcripts in the case of GT>GC substitutions remains unknown. Herein, combining data derived from a meta‐analysis of 45 human disease‐causing 5′SS GT>GC variants and a cell culture‐based full‐length gene splicing assay of 103 5′SS GT>GC substitutions, we estimate that ~15–18% of canonical GT 5′SSs retain their capacity to generate between 1% and 84% normal transcripts when GT is substituted by GC. We further demonstrate that the canonical 5′SSs in which substitution of GT by GC‐generated normal transcripts exhibit stronger complementarity to the 5′ end of U1 snRNA than those sites whose substitutions of GT by GC did not lead to the generation of normal transcripts. We also observed a correlation between the generation of wild‐type transcripts and a milder than expected clinical phenotype but found that none of the available splicing prediction tools were capable of reliably distinguishing 5′SS GT>GC variants that generated wild‐type transcripts from those that did not. Our findings imply that 5′SS GT>GC variants in human disease genes may not invariably be pathogenic.

ObjectivesRare pathogenic variants in the SPINK1, PRSS1, CTRC, and CFTR genes have been strongly associated with a risk of developing chronic pancreatitis (CP). However, their potential impact on the age of disease onset and clinical outcomes, as well as their potential interactions with environmental risk factors, remain unclear. These issues are addressed here in a large Chinese CP cohort.MethodsWe performed targeted next-generation sequencing of the four CP-associated genes in 1061 Han Chinese CP patients and 1196 controls. To evaluate gene–environment interactions, the patients were divided into three subgroups, idiopathic CP (ICP; n = 715), alcoholic CP (ACP; n = 206), and smoking-associated CP (SCP; n = 140). The potential impact of rare pathogenic variants on the age of onset of CP and clinical outcomes was evaluated using the Kaplan–Meier model.ResultsWe identified rare pathogenic genotypes involving the SPINK1, PRSS1, CTRC, and/or CFTR genes in 535 (50.42%) CP patients but in only 71 (5.94%) controls (odds ratio = 16.12; P < 0.001). Mutation-positive patients had significantly earlier median ages at disease onset and at diagnosis of pancreatic stones, diabetes mellitus and steatorrhea than mutation-negative ICP patients. Pathogenic genotypes were present in 57.1, 39.8, and 32.1% of the ICP, ACP, and SCP patients, respectively, and influenced age at disease onset and clinical outcomes in all subgroups.ConclusionsWe provide evidence that rare pathogenic variants in the SPINK1, PRSS1, CTRC, and CFTR genes significantly influence the age of onset and clinical outcomes of CP. Extensive gene–environment interactions were also identified.