The Protein Kinase C Alpha (PRKCA) gene is associated with multiple sclerosis in the Italian population

Multiple sclerosis (MS) is a chronic neurological disorder characterized by multicentric inflammation, demyelination, and axonal damage. The Protein Kinase C Alpha (PRKCA) gene was found to be associated with MS in Finnish, Canadian, and UK populations, in which specific risk haplotypes were identified. Moreover, PRKCA transcript levels were shown to be higher in CD4- mononuclear cells of MS patients carrying the risk haplotypes, suggesting a contribution of PRKCA regulatory mechanisms in the pathogenesis of MS. In this study, we analyzed the role of PRKCA in MS susceptibility in a cohort of 358 cases and 662 controls from continental Italy. An association analysis was performed genotyping 3 microsatellites and 20 single nucleotide polymorphisms (SNPs) covering the whole gene. A significant association with 2 microsatellites, mapping respectively in the promoter region and in intron 2, was found (P=0.032 and P=0.027). The 5’ regulatory region of the PRKCA gene was hence further investigated by sequencing the first 424 bp of the promoter and the entire exon 1 in all MS cases and controls. However, no genetic variants specific for MS cases were identified. Analysis of individual SNPs did not show any evidence for association; however, a haplotype of 7 SNPs, spanning a genomic region of 43 kb of PRKCA intron 3, resulted strongly associated with the disease status (P=7.4*10-4; OR=1.54, 95% CI=1.22-1.95). This haplotype, which partially overlaps the risk haplotypes observed both in Finns and Canadians, includes an alternative exon characterizing a shorter PRKCA protein isoform. Since no information were available on the tissue distribution of this isoform, its expression pattern was analyzed and compared to the expression profile of PRKCA in a panel of 20 human tissues by RT-PCR: the shorter isoform showed a more marked tissue-specific expression. The possible differential expression of the 2 transcripts between MS patients and controls is currently underway by qRT-PCR on RNA extracted from peripheral blood mononuclear cells. In conclusion, our study provides a strong replication evidence that haplotypes characterizing PRKCA increase the risk of MS; a metanalysis including all studies investigating the role of PRKCA as a MS susceptibility gene reported so far showed the considerable OR of 1.52 (95% CI=1.36-1.69; P=2.2*10-14).