PTEN c.511C>T Nonsense Mutation in a BRRS Family Disrupts a Potential Exonic Splicing Enhancer and Causes Exon Skipping

Abstract

Bannayan-Riley-Ruvalcaba syndrome (BRRS) is an autosomal dominant disorder characterized by macrocephaly, intestinal hamartomatous polyps, lipomas and pigmented macules of the glans penis. We identified a Thai family affected with BRRS. In addition to typical manifestations of BRRS, the proband has a large hepatic AVM which is rarely found in BRRS. The molecular analysis revealed affected members were heterozygous for an exon skipping-associated nonsense mutation c.511C>T in the PTEN gene. The mutation was previously assumed to be deleterious by causing a change to a termination codon, Q171X. We, herein, found that another pathogenic effect was splicing related by disrupting a potential exonic splicing enhancer (ESE) and causing an entire exon 6 skipping. The results prompted us to investigate other reported missense/nonsense mutations in the PTEN gene. We found that they do not colocalize with ESE sites, suggesting that most of their pathogenic effects are not through ESE disruption.