Prominin-1 and Retinal Degenerative Disorders: Expanding the Biology from Photoreceptors to the Retinal Pigment Epithelium.

Prominin-1 (Prom1/CD133) has long been recognized as a structural determinant of photoreceptor outer segment (OS) morphogenesis, yet rapidly accumulating evidence extends its role to retinal pigment epithelium (RPE) homeostasis, encompassing autophagy-lysosomal flux, outer segment phagocytosis, mitochondrial function, and regulation of inflammatory stress. This review synthesizes mechanistic and transcriptomic insights that position PROM1 as a central regulator of photoreceptor and RPE integrity, reframing Prom1 disease as a multi-compartment retinal disorder relevant to both inherited retinal dystrophies (IRDs) and atrophic age-related macular degeneration (aAMD). We develop a dual-axis conceptual model in which Prom1 dysfunction can initiate pathology in either the photoreceptors (OS morphogenesis failure) or the RPE, including impaired autophagic flux, lysosomal activity, defective phagocytosis, and Epithelial-Mesenchymal Transition (EMT)-like de-differentiation, with secondary cross-compartmental degeneration. Clinically, autosomal-dominant missense variants associate with macular or cone-rod dystrophy, whereas biallelic truncating/splice-site mutations drive early-onset rod-cone disease and panretinal/RPE atrophy, illustrating genotype-phenotype diversity. By integrating recent high-resolution transcriptomic data from Prom1-deficient RPE cells with long-standing insights into photoreceptor biology, we highlight converging pathways of degeneration that challenge a photoreceptor-centric view and unify disparate phenotypes within a single molecular framework. These insights broaden the therapeutic landscape, advancing gene augmentation and pathway-targeted strategies to preserve RPE integrity, sustain photoreceptor function, and modify disease course in PROM1-associated IRDs and atrophic AMD.