Co-inheritance of a novel deletion of the entire SPINK1 gene with a CFTR missense mutation (L997F) in a family with chronic pancreatitis

Abstract

Quantitative fluorescent multiplex PCR (QFM-PCR) was established in order to make possible the rapid and efficient mutational analysis of the pancreatic secretory trypsin inhibitor ( SPINK1) gene. Using QFM-PCR, a novel heterozygous deletion encompassing the entire SPINK1 gene was identified in one of nine newly recruited French Caucasian families with chronic pancreatitis. The breakpoints were fully characterized and the ∼30 kb deletion was termed c.1-15969_c.240+7702del30588bp. Whilst sequences with the potential to form non-B DNA structures were found to span both the 5′ and 3′ deletion breakpoints, the generation of this gross deletion is potentially explicable in terms of non-homologous end-joining facilitated by the presence of a 1-bp microhomology at the two ends. The SPINK1 gene deletion identified in the index patient was also detected in her affected father and paternal uncle but not in 50 healthy French Caucasians. Remarkably, in all three affected individuals, the SPINK1 deletion was found to be co-inherited with a heterozygous p.L997F missense mutation in the unlinked CFTR gene, a lesion previously reported to be associated with a variety of cystic fibrosis-related diseases including idiopathic pancreatitis. Given that the SPINK1 deletion constitutes a clear-cut disease-causing factor, it may be that the CFTR missense mutation acts as a disease modifier in the context of this particular family.