Analysis Of Autosomal Recessive Retinitis Pigmentosa Sporadic Genetic Screening And Clinical Phenotype

Purposes To identify the disease-causing genes and mutations of autosomal recessive retinitis pigmentosa (ARRP) and sporadic retinitis pigmentosa (SRP) in Chinese population, to analyze the clinical characters of ARRP/SRP, and to study the correlation between genotype and phenotype.Methods Patients diagnosed as ARRP/SRP in Peking Union Medical College Hospital during2009to2012were collected.1. Clinical study Medical history and family history were recorded, and patients were given general ophthalmic examinations (including vision acuity, optometry, anterior segment and fundus examination) and special ophthalmic examinations (fundus photograph, visual field (VF), electroretinogram (ERG) and optical coherence tomography (OCT)).2. Geneticstudy Venous blood samples (5-8ml) from patients and matched healthy volunteers were collected. Genomic DNA was isolated from peripheral leukocytes. Some DNA were sent to HuaDa genomic research center, the targeted exon sequences of the disease causing genes were specifically captured followed by HiSeq2000sequencing. We got the suspected mutations, all of which were validated by the polymerase chain reaction (PCR) amplification plus direct sequencing. Under the guidance of those results, the coding exons, including intron-exon boundaries, of the RHO, MERTK, PED6B, CERKL, RP1, USH2A and EYS gene were amplified by PCR, and the ampliations were sequenced directly. When mutations were found, by searching for the published papers and genetics databases, single nucleotide polymorphism (SNP) was excluded, whether the mutations had been reported was determined. If the mutation was novel, we amplified the loci and sequenced it in at least100normal subjects without consanguinity relationship, in order to exclude the unknown population polymorphisms.Results1.110probands were collected,108were bilateral and2were monocular.72.5%of patients had night blindness before age20, then the visual acuity was declined gradually, the best corrected visual acuity (BCVA) ranged from non-light perception (NLP) to1.5, the average BCVA is approximately0.2.36.8%of the affected eyes were complicated with posterior cataract. The main fundus appearance: optic-disc pallor, attenuated retinal arterioles, and intraretinal pigmentation in irregular/salted/bone-spicule configuration, mainly distributed in mid-periphery or far periphery. The macula can be nearly normal, or showed macula dystrophy. The OCT showed a flat fovea with reduced retinal thickness and abnormal retinal lamination. IS/OS signal disappeared. The average fovea thickness was125.15±39.68μm, significantly less than normal population (P<0.05); some of the patients had preretinal/premacula membrane, macula edema and capsular-like changes. The rod response was non-detectable in98.5%of the affected eyes.2. We identified the disease causing genes of18patients:11patients had mutation in MERTK gene,3in PDE6B gene,1each in USH2A, CERKL, RP1and EYS gene seperately. In addition,17patients had single heterozygotic mutation.①MERTK gene:mutation rate was6.9%,18mutations were found,3of them had been reported.4patients and6DNA halotype had the frame-shift mutation:225delA, Gly76Glu, fsX3. Both of the2cases of unilateral retinitis pigementosa (URP) had MERTK mutation.②PDE6B gene:5mutations were found, all of them were novel.③USH2A gene:4mutations were found,3of them were novel.④EYS gene:5mutations were found,5were all novel.⑤RP1gene:we found2novel mutations.⑥CERKL gene:1novel mutation.⑦RHO gene:1novel mutation.Conclusions1. Clinical feature:the age of onset of ARRP/SRP is usually in childhood and adolescence. Cataract is a common anterior segment abnormality; pigment epithelium migration is characteristic; damage of macula is very common, which showed reduced retinal thickness, and even macular atrophy, there could be preretinal/premacula membrane due to gliosis. ERG is an objective measure of retinal function, and the main change was non-detectable rod response.2. Ggenetic feature: the disease-causing genes of18patients were identified,36mutation loci in7genes were found. Among them, the mutation rate of MERTK gene (6.9%) is much higher than that of the western population. URP is probably related to MERTK gene mutation.3. RP is highly clinically and genetically heterogeneous, the same phenotype can attribute to several gene mutations, and the same gene mutation can lead to different clinical manifestations. The relationship between genotype and phenotype still needs further study.