PCYT1A Hypophosphorylation Underlies Retinal Lipid Dysregulation in CERKL Retinitis Pigmentosa and Is Therapeutically Reversed by Phosphatidylcholine.

Purpose: Retinitis pigmentosa (RP) is one of the main causes of hereditary blindness, and its genetic mode shows high heterogeneity. Among them, the mutation of the CERKL gene has been identified as the causative gene related to autosomal recessive hereditary RP. The underlying pathogenic mechanisms have remained obscure, hindering the development of effective therapies. This study aimed to elucidate the pathogenic mechanism linking CERKL deficiency to retinal degeneration and to identify a potential mechanism-based therapy. Methods: We used cerkl-/- zebrafish model, human retinal pigment epithelium (RPE)-1 cells, and utilized integrated multi-omics approaches (metabolomics, transcriptomics, and phosphoproteomics). Key findings were validated through lipid staining, biochemical assays, transmission electron microscopy (TEM), and rescue experiments. Results: CERKL deficiency triggered progressive lipid droplet (LD) accumulation in the RPE, associated with a profound reduction in phosphatidylcholine (PC) levels. Multi-omics integration revealed that PC deficiency stemmed from hypophosphorylation of the rate-limiting enzyme phosphate cytidylyltransferase 1A (PCYT1A) at a conserved serine residue (S331). Reconstitution of phosphomimetic PCYT1A (S331D) rescued LD pathology. Critically, exogenous PC supplementation alleviated LD accumulation, preserved photoreceptor outer segment structure, and improved retinal morphology in cerkl-/- zebrafish. Conclusions: Our work establishes dysregulated PC metabolism due to PCYT1A hypophosphorylation as a pathogenic driver in CERKL-deficient RP. We identify PC supplementation as a readily translatable, metabolic therapy for this genetically defined form of retinal degeneration.