Molecular Genetics And Resting Functional Magnetic Resonance Imaging Of Retinitis Pigmentosa

Part 1 Application of Targeted Panel Sequencing and Whole Exome Sequencing for Chinese Families with Retinitis PigmentosaBackground: This study aimed to identify the gene variants and molecular etiologies in 76 unrelated Chinese families with retinitis pigmentosa.Methods: In total,76 families with syndromic or non-syndromic retinitis pigmentosa,diagnosed on the basis of clinical manifestations,were recruited for this study.Genomic DNA samples from probands were analyzed by targeted panels or whole exome sequencing.Bioinformatics analysis,Sanger sequencing,and available family member segregation were used to validate sequencing data and confirm the identities of disease-causing genes.Results: The participants enrolled in the study included 62 families that exhibited non-syndromic retinitis pigmentosa,13 that exhibited Usher syndrome,and one that exhibited Bardet-Biedl syndrome.We found that 43 families(56.6%)had disease-causing variants in 15 genes,including RHO,PRPF31,USH2 A,CLRN1,BBS2,CYP4V2,EYS,RPE65,CNGA1,CNGB1,PDE6 B,MERTK,RP1,RP2,and RPGR.The gene most frequently found in the study is USH2A(19.7%),followed by CYP4V2(6.6%).Moreover,12 families(15.8%)had only one heterozygous variant in seven autosomal recessive retinitis pigmentosa genes,including USH2 A,EYS,CLRN1,CERKL,RP1,CRB1,and SLC7A14.We did not detect any variants in the remaining21 families(27.6%).We also identified 67 potential pathogenic gene variants,these included 37 missense variants(55.2%),11 nonsense variants(16.4%),one small indel variant(1.5%),10 small deletion variants(14.9%),two small insertion variants(3.0%),and six splice variants(9.0%).Twenty-four variants had not previously been reported.Conclusion: The gene variants identified in this study expand the variant frequency and spectrum of retinitis pigmentosa genes;moreover,the identification of these variants supplies foundational clues for future retinitis pigmentosa diagnosis and therapy.Part 2 Altered intra-and inter-regional functional connectivity of the visual cortex in individuals with peripheral vision loss due to retinitis pigmentosaPurpose: This study investigated changes in resting intra-and inter-regional functional connectivity of the brain in individuals with retinitis pigmentosa by using regional homogeneity and functional connectivity methods.Methods: We enrolled sixteen retinitis pigmentosa individuals and 14 healthy controls subjects,all of them underwent resting-state functional magnetic resonance imaging scans.Two-sample t-tests were performed to compare regional homogeneity and functional connectivity differences of visual cortex between groups.Pearson correlation was used to analyze relationships between regional homogeneity and functional connectivity and clinical variables in the retinitis pigmentosa group.Results: Compared with healthy controls,retinitis pigmentosa individuals had significantly lower regional homogeneity values in the bilateral lingual gyrus/cerebellum posterior lobe.In functional connectivity analysis,the retinitis pigmentosa group showed decreased positive functional connectivity relative to the healthy controls group,from bilateral lingual gyrus/cerebellum posterior lobe to bilateral lingual gyrus /cuneus and to left postcentral gyrus.In contrast,the retinitis pigmentosa group showed increased negative functional connectivity relative to the healthy controls group,from bilateral lingual gyrus/cerebellum posterior lobe to bilateral thalamus,and decreased negative functional connectivity from bilateral lingual gyrus/cerebellum posterior lobe to right middle frontal gyrus,and to left inferior parietal lobule.Moreover,regional homogeneity values of the bilateral lingual gyrus/cerebellum posterior lobe showed negative correlations with the duration of retinitis pigmentosa.functional connectivity values of the bilateral lingual gyrus/cerebellum posterior lobe-left inferior parietal lobules showed negative correlations with best-corrected visual acuity of the right eye and left eye in retinitis pigmentosa individuals.Conclusions: Our results reveal reduced synchronicity of neural activity changes in the primary visual area in retinitis pigmentosa individuals.Moreover,retinitis pigmentosa individuals showed intrinsic visual network disconnection and reorganization of the retino-thalamocortical pathway and dorsal visual stream,suggesting impaired visuospatial and stereoscopic vision.Decreased synchrony is associated with disease severity,and it may provide a reference index for evaluating the efficacy of RP in the future.Part 3 Arterial spin labeling perfusion magnetic resonance imaging reveals resting cerebral blood flow alterations specific to retinitis pigmentosa patientsPurpose: This study aimed to assess resting cerebral blood flow changes in retinitis pigmentosa patients using a pseudo-continuous arterial spin labeling perfusion method.Methods: We enrolled forty-nine retinitis pigmentosa patients and 51 healthy controls subjects,all of them underwent T1-weighted structural and pseudo-continuous arterial spin labeling sequence magnetic resonance imaging scans at rest.Two-sample t-tests were performed to compare cerebral blood flow differences between groups.Pearson correlation was used to analyze relationships between cerebral blood flow values and clinical variables in the retinitis pigmentosa group.Results: Compared with healthy controls,retinitis pigmentosa patients had significantly lower cerebral blood flow values in the bilateral cuneus/lingual gyrus/precuneus/posterior cingulate/middle occipital gyrus.In the retinitis pigmentosa group,cerebral blood flow values in the left middle occipital and inferior occipital gyrus were positively correlated with mean retinal nerve fiber layer thickness;cerebral blood flow values in the left inferior occipital gyrus,right cerebellum anterior lobe,and left precuneus/cuneus were positively correlated with age of RP onset;cerebral blood flow values in the bilateral cerebellum anterior lobe,left inferior occipital gyrus,and left precuneus were negatively correlated with duration of RP.Conclusions: Our results highlighted that retinitis pigmentosa patients exhibited decreased cerebral blood flow values in the visual cortices and vision-related cortices.The results suggest that altered cerebral blood flow might contribute to trans-synaptic retrograde degeneration of the visual pathway in retinitis pigmentosa patients.Decreased cerebral blood flow is associated with disease severity,and,it may provide a reference index for evaluating the efficacy of RP in the future.