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We read with interest the recent publication of Beer and Sahin-Tóth1 reporting that exonic variants affecting pre-mRNA splicing contribute to the genetic burden in chronic pancreatitis. One particular variant, affecting the last nucleotide of exon 3 of the SPINK1 gene, c.194G>A, was found to cause an ∼80% reduction in SPINK1 mRNA expression as compared with the wild type in a minigene assay performed in human embryonic kidney 293T (HEK293T) cells. The SPINK1 sequence inserted into the minigene expression vector however comprised only exon 1, exon 2, exon 3, intron 3 and exon 4 of the four-exon gene.1 It should be noted that the potential effect of c.194G>A as a missense mutation (p.Arg65Gln) on protein function has previously been analysed; engineered expression of the full-length mutant coding sequence in Chinese hamster ovary cells and HEK293T cells showed a consistent 50%–60% reduction in protein secretion as compared with the wild type.2 ,3
We recently analysed the functional consequences of 24 SPINK1 intronic variants in relation to their associated mRNA splicing phenotypes4 ,5 by means of a full-gene splicing assay in which the full-length 7 kb SPINK1 genomic sequence (including all four exons plus all three introns of the gene) was cloned into the pcDNA3.1/V5-His-TOPO vector.6 This full-length gene expression system has already proved itself in practice by accurately representing the in vivo situation in the context …
Contributors J-MC, ZL, Z-SL and CF designed and directed the study. HW and AB performed functional analysis. J-MC drafted the manuscript. DNC critically revised the manuscript. All authors analysed the data and approved the final manuscript.
Funding HW is a joint PhD student between the Changhai Hospital and INSERM U1078 who was in receipt of a 1-year scholarship from the China Scholarship Council (No. 201503170355). Support for this study came from the National Natural Science Foundation of China (Grant Nos. 81470884 and 81422010; to ZL), the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission (Grant No. 15SG33; to ZL), the Chang Jiang Scholars Program of Ministry of Education, People's Republic of China (Grant No. Q2015190; to ZL); the Conseil Régional de Bretagne, the Association des Pancréatites Chroniques Héréditaires, the Association de Transfusion Sanguine et de Biogénétique Gaetan Saleun, the Institut National de la Santé et de la Recherche Médicale (INSERM), France.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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