DNA Methylation Dynamics in a Mouse Model of Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a group of sight-threatening genetic diseases characterized by progressive degeneration of photoreceptors, leading to severe vision loss from childhood to adulthood. With limited treatment options, understanding the molecular mechanisms underlying RP is crucial. Increased DNA methylation, especially in degenerating photoreceptors, is a contributing factor to retinal damage in RP. To exploit the molecular insights into methylation-driven pathways, this study investigated the DNA methylation patterns and their potential roles in photoreceptor degeneration in a mouse model of RP, specifically mice carrying a rhodopsin deficiency (Rho^–/–). Elevated levels of DNA methyltransferases (DNMTs) and DNA methylation were observed during photoreceptor degeneration. Importantly, weekly intravitreal injections of the pan DNMT inhibitor decitabine in Rho^–/– mice significantly improved photoreceptor morphology and visual function, as evidenced by electroretinogram, spectral-domain optical coherence tomography, and optomotor response-based visual behavior assays. Further histologic and immunohistochemical assessments revealed increased survival of cone photoreceptors and thicker outer nuclear layers in decitabine-treated mice compared with controls. Together, these findings revealed that the dynamics of DNA methylation correlate with photoreceptor degeneration. Inhibition of DNMTs mitigated the morphologic and functional impairments associated with the genetic defects in photoreceptors, suggesting that targeting DNA methylation could be a viable therapeutic strategy for neuroprotection in RP.