Correlative Study For Retinitis Pigmentosa With Retinal Vascular Occlusion

Objective:Retinitis pigmentosa is a group of common disorders of dystrophy that characterized by inherited progressive dysfunction,photoreceptor and retinal pigment epithelium cell loss,and eventually atrophy of retinal tissue.Retinitis pigmentosa with retinal progressive vascular occlusion has been recognized step by step in recent years.There were few domestic case reports once named "Primary bilateral vaso-obliterative optic neuro-retinopathy" which focused on vascular occlusion with unknown cause,but the similar paperwork has not been found abroad.After collection of the supplementary materials needed,summarizing clinical features of retinitis pigmentosa with retinal vascular occlusion and exome sequencing not ever done in the past were in the hope of interpreting pathogenetic mechanism and identifying my initial impression in this doctor dissertation.Methods:The clinical data in 23 cases(46eyes)including 12 cases M,11 cases F,ages from 6-70 average 49.96 ± 15.80 yrs,both eyes affected,history of nyctalopia,were retrospectively analyzed with fundus examination,fundus fluorescein angiography,indocyanine green angiography,electroretinogram,visually evoked potential etc.Exome sequencing was performed in 8 blood samples(6 from patients,and 2 from 1 patient’ parents).Experimental and analytical approaches relating to exome sequencing have established a rich framework for discovering the genes underlying unsolved disorders.There are 3 main steps include target enrichment strategies,Bio-information science statistics,molecular inversion probes,Sequencing of DNA,etc.When the result is available,we analyzed more than or equal to two case’common sites,,with focusing on the sites which were not included in single nucleotide polymorphism database,which may be the potential new site related to RP.The further concentration is choosing missense variant etc.which could lead to Amino acid change,in order to find the comparatively obvious change of the function.Under this condition,there were about 300 sites and 81 genes.Then set the filtering standard with the depth more than 10 and the quality more than 20.Next,we analyzed the potential sites with functional enrichment analysis,which is mentioned in the Kyoto Encyclopedia of Genesand Genomes and Gene ontology.By utilizing the above result,We tried to find the potential sites and pathogenic genes considering the real clinical experience.Results:The major clinical manifestations of the disease:no inflammation in the anterior segment,opacity of lens(20 eyes),no neo-vascularization in the iris,normal intraocular tension.In the fundi,all optic discs showed pale,some showed heavily atrophic like the moon(17 eyes).All the retinal vessels became attenuated,more pronounced in the nasal part.Owing to different course of the disorder,there appeared different levels of vascular occlusion,even total occlusion&disappearance in later stage.Widespread retinal atrophy with depigmentation and/or fine pigment spots,and with no typical bone corpuscle.No retinal neo-vascularization,no proliferative retinopathy,no vitreous hemorrhage,and no retinal exudation and bleeding appeared.Fundus Fluorescein Angiography revealed total hypo-fluorescence or faint fluorescence in later stage at the disc(20 eyes),a small segment of fluorescence at the disc(17 eyes).ICGA revealed narrowed choroidal vessels,weak fluorescence and faster fluorescent regression.The other ICGA manifestations were identical to that of FFA.Electroretinogram revealed total or nearly total a and b wave extinction.Night blindness could be seen in patients.Eight samples were analysed by Whole exome sequencing.In the results,we found the SNP related RP,which had been reported previously.Again we found new mutation sites in some encoding regions which caused the change of amino acid.These sites have relations with cellular processes such as apoptosis,neurodegeneration,inhibited proliferation,through gene annotation.Then we apply KEGG and GO to find biological related pathway.There exist many pathways such as apoptosis,axon guidance,VEGF signaling pathway,vitamine B6 metabolism pathyway etc.Conclusion:The main fundus changes of the patients in the study included pale disc,vessel attenuation,massive retinal atrophy,with depigment spots and with or without tiny pigment spots.ERG showed a,b wave extinction.All this manifestations were compatible with that of typical Retinitis Pigmentosa(tapeto-retinal dystrophy).But it also had its unique features:1.Total or nearly total vascular obliteration,marked moon-like optic atrophy in later stage,and choroidal vessels abnormal.2.Retinal pigment epithelium atrophy with depigmentation,without bone spicules.No retinal neovascularization,non proliferative retinopathy and vitreous hemorrhage.3.The course of the disorder seemed to carry on faster than typical retinitis pigmentosa.Retinitis pigmentosa with retinal vascular occlusion may be one of the phynotypes of RP according to its clinical characteristics.Single Nucleotide Polymorphism(SNP)sites related RP were found in the results of exome sequencing.lt is still under investigation that whether the sites have functional relation with RP.Many unknown gene mutation sites which lead to amino acid modified were tried to explain the reason of vascular occlusion.Gene annotation found that these sites were related to apoptosis,neurodegeneration,inhibited proliferation.Also,some genes participated in metabolism pathyway:apoptosis,axon guidance,VEGF signaling pathway,vitamine B6 etc.Metabolic pathways provided by KEGG and GO try to explain these clinical manifestations from biological function aspect.But the further experiments and studies are necessary for exact results.