Hereditary cancer genes are highly susceptible to splicing mutations

Substitutions that disrupt pre-mRNA splicing are a common cause of genetic disease. On average, 13.4% of all hereditary disease alleles are classified as splicing mutations mapping to the canonical 5′ and 3′ splice sites. However, splicing mutations present in exons and deeper intronic positions are vastly underreported. A recent re-analysis of coding mutations in exon 10 of the Lynch Syndrome gene, MLH1, revealed an extremely high rate (77%) of mutations that lead to defective splicing. This finding is confirmed by extending the sampling to five other exons in the MLH1 gene. Further analysis suggests a more general phenomenon of defective splicing driving Lynch Syndrome. Of the 36 mutations tested, 11 disrupted splicing. Furthermore, analyzing past reports suggest that MLH1 mutations in canonical splice sites also occupy a much higher fraction (36%) of total mutations than expected. When performing a comprehensive analysis of splicing mutations in human disease genes, we found that three main causal genes of Lynch Syndrome, MLH1, MSH2, and PMS2, belonged to a class of 86 disease genes which are enriched for splicing mutations. Other cancer genes were also enriched in the 86 susceptible genes. The enrichment of splicing mutations in hereditary cancers strongly argues for additional priority in interpreting clinical sequencing data in relation to cancer and splicing.Author summary: To understand the extent to which disrupted pre-mRNA splicing causes human disease, we re-analyzed coding mutations in MLH1, one of the causal genes of Lynch Syndrome. We found that a high fraction of the MLH1 coding mutations resulted in disrupted splicing. To further investigate a more general role of defective splicing across human disease genes, simulation strategies were used to identify 86 disease genes prone to splice site mutations. In these 86 genes, there was an enrichment of cancer genes including the three main casual genes of Lynch Syndrome (MLH1, MSH2, and PMS2). Thus, it appears defective splicing may be the main driver of Lynch Syndrome and other cancers. Genes prone to splicing mutations have certain features that allow for the comprehensive prediction of splicing-prone diseases genes in the human genome. Our findings strongly argue for additional clinical sequencing prioritization in both cancer genes and genes prone to splice site mutations.