Developmental regulation of melanopsin-containing retinal ganglion cells and its effects on circadian function

Light input from the retina entrains the circadian clock in the suprachiasmatic nucleus via melanopsin‑expressing intrinsically photosensitive retinal ganglion cells (ipRGCs). This study tested whether outer retinal development influences ipRGC maturation and adult circadian function using retinally degenerate CBA/J mice. Behavioral assays revealed impaired photoentrainment despite intact melanopsin signaling at the retinal level. Photoreceptor loss increased ipRGC numbers without altering their morphology, suggesting regulation of developmental cell death. Central analyses showed alterations in SCN neuropeptide composition and enhanced light‑induced activation. Together, these findings indicate that visual system maturation shapes central circadian circuitry and behavior.