CyclinD2-mediated regulation of neurogenic output from the retinal ciliary margin is perturbed in albinism

In albinism, aberrations in the ipsi-/contralateral retinal ganglion cell (RGC) ratio compromise the functional integrity of the binocular circuit. We focus here on the mouse ciliary margin zone (CMZ), a neurogenic niche at the embryonic peripheral retina, to investigate developmental processes regulating RGC neurogenesis and identity acquisition. We found that the mouse ventral CMZ has the competence to generate predominantly ipsilaterally-projecting RGCs, but this competence is altered in the albino visual system due to CyclinD2 downregulation and disturbed temporal control of the cell cycle. Consequently, albino as well as CyclinD2-deficient pigmented mice exhibit a diminished ipsilateral retinogeniculate projection and compromised depth perception. Pharmacological stimulation of calcium channels in albino mice, known to upregulate CyclinD2 in other cell types, augmented CyclinD2-dependent neurogenesis of ipsilateral RGCs, and improved stereopsis. Together, these results implicate CMZ neurogenesis and its regulators as critical for the formation and function of the mammalian binocular circuit. Highlights The mouse ventral CMZ produces predominantly ipsilateral RGCs. In the albino visual system, CyclinD2 downregulation leads to delayed G1/S transition toward mitotic exit of CMZ progenitors. Perturbations in the temporal control of cell cycle by CyclinD2 lead to reduced Zic2 + RGCs and consequently, a diminished ipsilateral retinogeniculate projection and compromised depth perception. Calcium channel modulation during embryogenesis normalizes the levels of CyclinD2 and restores binocular vision in albino mice.