New splicing mutations in propionic acidemia

Propionic acidemia results from mutations in either of the two genes, PCCA or PCCB, that encode the two subunits of the propionyl-CoA carboxylase (PCC) enzyme. In this study, we report the identification and analysis of seven novel splicing mutations involving consensus donor and acceptor splice sites. Most of them were identified in patients with a Central Asian origin, and some present in several alleles, probably reflecting founder effects. The functional consequences of the splicing mutations were analyzed in patients' fibroblasts, as well as transcript quantification using real-time PCR methods. In the PCCA gene, two mutations were demonstrated to affect 5' splice sites (c.231+1G>C and c.1209+3A>G) and two 3' acceptor splice sites (c.1210delG and c.1430G>T), all causing skipping of the exons involved, with no detectable levels of normally spliced transcript. In the PCCB gene, all three mutations involved 5' donor splice sites-two affected exon 1 splicing (c.154_183+17del46 and c.183+2T>C), the latter activating a cryptic splice site in intron 1, and the remaining mutation (c.1498+2T>C) resulted in exon 14 skipping. The results highlight the necessity to perform transcript analysis in addition to genomic DNA sequencing to characterize the effect of splicing mutations and add relevant information on the genetic epidemiology of the disease.