A Novel Splice-Site Mutation in MSH2 Is Associated With the Development of Lynch Syndrome

Abstract

Lynch syndrome (LS) is an inherited autosomal dominant disorder caused by germline mutations of mismatch repair (MMR) genes, including MSH2, MSH6, PMS2, and MLH1. This study aimed to analyze the molecular defects and clinical manifestations of an affected family and propose appropriate individual prevention strategies for all mutation carriers. A novel splicing mutation (c.1661+2 T>G) was identified in the MSH2 gene, which was found to co-segregate among affected family members by Whole exome sequencing (WES). RT-PCR analysis confirmed that c.1661+2 T>G could produce 3 transcripts, including 1 normal transcript and 2 aberrant transcripts. The 2 aberrant transcripts resulted in premature termination at the 6th nucleotide codon of MSH2 exon 11, so that the predicted products of the mutant MSH2 mRNAs were truncated proteins of 505 amino acids (with all of exon 10 deleted) and 528 amino acids (with a deletion of 82-nucleotides in exon 10), resulting in the loss of the interaction domain, the ATP domain and post-translationally modified residues. Quantitative RT-PCR (qRT-PCR) analysis showed that MSH2 mRNA levels in all patients were reduced to only 1/4 of the control levels. Our study reveals that a novel splicing mutation (c.1661+2 T>G) in the MSH2 gene causes LS and reaffirms the importance of genetic testing for LS.

Keywords: Lynch syndrome; MSH2; aberrant splicing; genetic counseling; hereditary non-polyposis colorectal cancer; microsatellite instability.