Three exonic mutations in polycystic kidney disease-2 gene (PKD2) alter splicing of its pre-mRNA in a minigene system

• Thirteen PKD2 exonic mutations were studied in minigenes and three of them produced alterations in pre-mRNA splicing
• Mutation c.1532A > T (p.D511V) caused skipping of exon 6 and incorporation of exon 6 lacking its 3′ end
• Synonymous variant c.1716G > A (p.K572K) led to exon 7 skipping
• Mutation 2657A > G (p.D886G) resulted in incorporation of an incomplete exon 14 in the mRNA
• These results highlight the importance to evaluate the effects of exonic single nucleotide substitutions in ADPKD

Exonic mutations are usually classified as missense, synonymous or nonsense mutations, however, they can affect pre-mRNA splicing either by disrupting splice sites, by creating new ones or by changing splicing regulatory sequences. In this study, we examined 21 mutations of the PKD2 gene, encoding polycystin-2, previously reported as missense or synonymous for their possible effects on pre-mRNA splicing using bioinformatics tools. All these mutations except one have been identified in patients with autosomal dominant polycystic kidney disease, a common genetic disorder characterized by the development and progressive enlargement of cysts in the kidneys leading to end-stage renal disease. We selected 12 missense mutations and 1 synonymous variant for the minigene assay, and found that three, c.1532A > T (p.D511V), c.1716G > A (p.K572K) and c.2657A > G (p.D886G) caused alterations in pre-mRNA splicing. Mutation c.1532A > T resulted in skipping of exon 6 and incorporation of a defective exon lacking the 3′ end, while c.1716G > A led to skipping of exon 7. Mutation c.2657A > G resulted in incorporation of an incomplete exon 14, which is in agreement with previous results obtained with the patient's lymphoblast RNA. Our findings should be taken into account with regard to the pathogenicity of these PKD2 exonic mutations. These results together with previous reports highlight the importance to evaluate the effects of exonic single nucleotide substitutions in autosomal dominant polycystic kidney disease.