Co-occurrence of Parkinson's disease and Retinitis Pigmentosa: A genetic and in silico analysis

Introduction: Parkinson's disease (PD) is primarily driven by the protein Alpha Synuclein (A-Syn) accumulation. Synphilin-1 protein, encoded by the SNCAIP gene, which co-localizes with A-Syn is a known risk factor for PD. Retinitis pigmentosa (RP), is a cluster of retinal degenerative disorders, and Cyclic Nucleotide Gated channel subunit Alpha 1 (CNGA1) is one of the initial genes associated with RP. Patients with PD can have various kinds of visual dysfunction as a non-motor manifestation, but to date, CNGA1 mutation and RP as a PD associated visual symptom has not been reported. We report a mutation in the SNCAIP gene in a PD patient, not reported earlier, and its co-occurrence with RP-associated CNGA1 gene mutation. Method: Whole exome sequencing (WES) of the patient DNA sample and in-silico protein-protein interaction (PPI) analysis performed to find out proteins interacting with SNCAIP relevant concerning reported mutation of SNCAIP and further, CNGA1 interaction with SNCAIP. Result: We are reporting, a missense mutation (p.Thr64Ser) at the SNCAIP gene, co-occurring with a missense variation (p.Gly509Arg) in the CNGA1 gene. In silico PPI analysis suggests SIAH1 as an important protein affected by SNCAIP mutation. LGALS4 and SNCA (gene encoding A-Syn) are common interactors between SNCAIP and CNGA1. Conclusion: The current study has determined the co-occurrence of RP and PD, whole exome sequencing ascertains the mutations in SNCAIP and CNGA1 genes, which could be the cause of PD and RP co-occurrence.