Samd7, short for sterile alpha motif domain containing 7, is a component of the Polycomb repressive complex 1 (PRC1). It plays a crucial role in transcriptional regulation, inhibiting the transcription of many genes, especially those activated by the transcription factor Cone-Rod Homeobox (CRX). It is essential for retinal function and is involved in pathways related to photoreceptor cell identity establishment and gene expression regulation in the retina [1,3,5].

In Samd7-null mutant mice, non-rod genes like S-opsin are ectopically expressed in rod photoreceptor cells, leading to rod photoreceptor cell dysfunction [3]. In zebrafish, loss of Samd7 results in red cones transforming into hybrid red/ultraviolet (UV) cones, absence of green cones, an approximate doubling of blue cones, and a significant reduction in the number of rods [2]. Also, in the Samd7/11 double-knock-out (DKO) mouse retina, photoreceptor outer segments are shortened, and more retinal genes are up-regulated compared to Samd7 -/- alone, indicating partial functional redundancy between Samd7 and Samd11 [4].

In conclusion, Samd7 is vital for maintaining appropriate gene expression patterns in rods and cone subtypes, thus ensuring normal retinal function. Studies using gene-knockout mouse models have revealed its role in preventing non-rod gene expression in rod photoreceptor cells and in establishing correct photoreceptor cell identities. These findings contribute significantly to understanding autosomal-recessive macular dystrophy and other retinal-related diseases [1,3].