An Autosomal Dominant Retinitis Pigmentosa Family Genes That Cause Positioning And Identification

One large Chinese family with autosomal dominant retinitis pigmentosa was investigated from which 34 individuals were sampled and used for linkage analysis ,Twenty individuals were considered to be affected and 14 were designated as having uncertain status.The genome scan was conducted using the ABI 377 automated DNA sequencer (Applied Biosystems). We have set up a multiple PCR system with the high-efficiency Ampli Taq Gold?polymerase for genome scan . In this system, the annealing temperature decreases progressively in a certain scale. A negative control sample and two positive control samples of known genotype (CEPH sample 1347-02) were tested,as a quality control,on each gel. ABI Prism?377XL Collection sofeware was used to collect the data,to track lanes,to estimate fragment sizes and to check internal size standards. Genotypes were assigned using the Genotyper software.Two-point LOD score was calculated using the MLINK routine of the LINKAGE software package, version 5.1.The strongest evidence of linkage was detected with three adjacent microsatellite markers genotyped between d19s402 and d19s210 on chromosome 19ql3.33-13.43.The maximum two-point LOD score of 2.79 was obtained at 0=0.1 for marker D19S418.Three genes CRX,PRPF31 and PRKCG that are led with ADRP have been mapped within the region of interest(i.e.between markers d19s402 and d19s210).To identify the causative gene for ADRP in this family, we directly sequenced these candidate genes, We found a single nucleotide change (G~*A) at the position -1 of the intron 5 of PRPF31 gene. The consensus AG doublet of the intron 5 splicing acceptor was changed to AA. This splicing site mutation is predicted to cause an erroneous splicing of exon 6. The exon 6 of PRPF31 is 107bp in site. Skipping of exon 6 will generate a premature stop codon in exon 8, leading to a truncated protein which has only N-terminal 140 amino acid, with additional 12 amino acid. The PRPF31 encodes a 61 KD protein with 499 amino acid. The truncated protein is predicted to loss the major functional domains of this protein.Thus, this splicing acceptor site mutation is predicted to be a loss of function mutation, although dominant negative effect can not be completely excluded. Identification of exon skipping mutation in this Chinese family is the first mutation of this kind in PRPF31 gene. We propose that a loss of function or haplotype insufficiency is the mechanism underlying this disease.It was first report that this mutation be found in PRPF31 gene.