Regulatory Mechanisms of Retinal Photoreceptors Development at Single Cell Resolution

Abstract

Photoreceptors are critical components of the retina and play a role in the first step of the conversion of light to electric signals. With the discovery of the intrinsically photosensitive retinal ganglion cells, which regulate non-image-forming visual processes, our knowledge of the photosensitive cell family in the retina has deepened. Photoreceptor development is regulated by specific genes and proteins and involves a series of molecular processes including DNA transcription, post-transcriptional modification, protein translation, and post-translational modification. Single-cell sequencing is a promising technology for the study of photoreceptor development. This review presents an overview of the types of human photoreceptors, summarizes recent discoveries in the regulatory mechanisms underlying their development at single-cell resolution, and outlines the prospects in this field.

Vision and retina evolution: How to develop a retina

“…A single atonal -like gene does resemble the net genes of Drosophila but is considered an Orphan bHLH gene rather than indicating an ancient origin of Atoh 7 ( Cao et al, 2019 , Chen et al, 2011 ). Further, as shown in following sections, the ciliary sensory cells of vertebrates end in a synaptic ribbon which contacts secondary sensory cells and is also under control of Atoh7 ( Zhao and Peng, 2021 ) . Gene expression that resembles certain aspects of other chordates is known among lancelets ( Holland, 2020 ).…”

“…From the point of view of eye evolution, the central projections of vertebrate retina arise from ganglion cells that express the basic helix-loop-helix (bHLH) gene Atoh7 ( Brzezinski and Reh, 2015 , Chan et al, 2020 , Zhao and Peng, 2021 ). The Atoh 7 gene is not present in the lancelet ( Holland, 2020 , Holland et al, 2008 ).…”

“…The sequence of development of different retinal cell types in gnathostomes (jawed vertebrates) has been established following the initial discovery of proliferation of a column of retinal cells ( Cepko et al, 1996 ). The earliest stage is the formation of RGCs: this process depends on the transcription factor Atoh7 in all vertebrates ( Baker and Brown, 2018 , Wu et al, 2021 , Zhao and Peng, 2021 ). Downstream of Atoh7 are Brn3b / Pou4f2 and Isl1 and the distalless homolog ( Dlx2 ) which is not regulated by Atoh7 ( Brzezinski and Reh, 2015 , Cao et al, 2019 ).…”