Mutation Screening of Four Candidate Genes, KHDRBS2, PTP4A1, KIAA1411, and OGFRL1, in the Autosomal Recessive Retinitis Pigmentosa (RP25) Critical Interval

Abstract

Abstract: : Purpose:To identify the disease gene in 6 Spanish families with autosomal recessive retinitis pigmentosa (arRP) linked to the RP25 locus. Mutation screening of four candidate genes, KHDRBS2, PTP4A1, KIAA1411, and OGFRL1, was undertaken. The genes were selected as good candidates on the basis of their function, tissue expression pattern or genetic data. Methods: A molecular genetic study was performed on DNA extracted from one parent and one affected member of each studied family. The genomic structure of the candidate genes was determined using bioinformatics. The coding exons and splice sites of all the studied genes were amplified by polymerase chain reaction (PCR) using primers located in the flanking intron and untranslated sequences. For mutation detection, direct sequence analysis was performed using the ABI 3100 automated sequencer. Retinal expression of the studied genes was assessed by PCR amplification of human cDNA from retina. Results:All studied genes showed retinal expression as detected by PCR. An additional exon was identified in the KIAA1411 gene through examination of multiple cDNA transcripts. 24 single nucleotide polymorphisms (SNPs) were identified, three of them change the encoded amino acid and another two are deletions of 3 and 5 base pairs. These changes, however, were also identified in unaffected members of the families and/or 50 control Caucasians. Conclusions: The studied genes were excluded as the causative genes for the RP25 families. However, we could not rule out these genes as good candidates for other retinal degenerations mapping to the same chromosomal region. Further bioinformatic analysis of the region may identify additional candidate genes for RP25.

Keywords: candidate gene analysis • gene/expression • retina