A novel 7 bp deletion in PRPF31 associated with autosomal dominant retinitis pigmentosa with incomplete penetrance in an Indian family

Abstract

To localize and identify the gene linked with non-syndromic autosomal dominant retinitis pigmentosa (adRP) with high but not complete penetrance in an Indian family. A detailed family history and clinical data were recorded. A genome-wide scan by 2-point linkage analysis using nearly 400 fluorescently labeled microsatellite markers in combination with multipoint lod score and haplotype analysis was carried out. Mutation screening was performed in the candidate gene by bidirectional sequence analysis of the amplified products. A maximum 2-point lod score of 3.553 at theta = 0.0 was obtained with marker D19S572. Haplotype analysis placed the RP locus distal to marker D19S572, in close proximity to the gene for pre-mRNA processing factor 31 (PRPF31) at 19q13.42. Mutation screening in all 14 exonic regions and adjacent flanking intronic sequences of PRPF31 revealed a novel 7 bp deletion, c.59_65del7 (p.Gly20AlafsX43), in the first coding exon of PRPF31. This leads to a premature termination codon (PTC) in the next exon, 43 amino acids downstream. The observed 7 bp deletion in PRPF31 was identified in all the tested 10 affected members and in an unaffected individual, consistent with a high, but not the complete penetrance of c.59_65del7 (p.Gly20AlafsX43). This deletion was not observed in other tested six unaffected family members or in 100 ethnically matched control subjects. The present study describes mapping of a locus for non-syndromic adRP at 19q13.42 (RP11 locus) in a family of Indian origin and identifies a novel deletion, c.59_65del7, in PRPF31 within the mapped interval. Since the mutant PRPF31 is truncated relatively close to the N-terminus of the protein, haploinsufficiency rather than aberrant protein formation is likely to be the underlying mechanism of the disease. The present findings further substantiate the role of PRPF31 that encodes a component of the spliceosome complex in relation to ADRP.