The Atoh7 remote enhancer provides transcriptional robustness during retinal ganglion cell development

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 35; pp. 21690 - 21700
• Main Authors: Miesfeld, Joel B., Ghiasvand, Noor M., Marsh-Armstrong, Brennan, Marsh-Armstrong, Nicholas, Miller, Eric B., Zhang, Pengfei, Manna, Suman K., Zawadzki, Robert J., Brown, Nadean L., Glaser, Tom
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 01-09-2020
• Subjects: Animals; Aplasia; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Biological Sciences; Blindness; Cell Differentiation; Chromatin; Competence factor; Embryo, Mammalian - metabolism; Female; Gene deletion; Gene Expression Regulation, Developmental - genetics; Genomes; Heterozygotes; Histogenesis; Male; Mice; Mice, Inbred C57BL; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Nerves; Neurogenesis - physiology; Non-coding RNA; Optic nerve; Optic Nerve - metabolism; Regulatory Sequences, Nucleic Acid - genetics; Retina; Retina - metabolism; Retinal ganglion cells; Retinal Ganglion Cells - metabolism; Retinal Ganglion Cells - physiology; Transcription; Transcription Factors - metabolism; Vertebrates; shadow enhancer; human genetic disorders; optic nerve; glaucoma; optic disc area
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2006888117

The retinal ganglion cell (RGC) competence factor ATOH7 is dynamically expressed during retinal histogenesis. ATOH7 transcription is controlled by a promoter-adjacent primary enhancer and a remote shadow enhancer (SE). Deletion of the ATOH7 human SE causes nonsyndromic congenital retinal nonattachment (NCRNA) disease, characterized by optic nerve aplasia and total blindness. We used genome editing to model NCRNA in mice. Deletion of the murine SE reduces Atoh7 messenger RNA (mRNA) fivefold but does not recapitulate optic nerve loss; however, SEdel/knockout (KO) trans heterozygotes have thin optic nerves. By analyzing Atoh7 mRNA and protein levels, RGC development and survival, and chromatin landscape effects, we show that the SE ensures robust Atoh7 transcriptional output. Combining SE deletion and KO and wild-type alleles in a genotypic series, we determined the amount of Atoh7 needed to produce a normal complement of adult RGCs, and the secondary consequences of graded reductions in Atoh7 dosage. Together, these data reveal the workings of an evolutionary fail-safe, a duplicate enhancer mechanism that is hardwired in the machinery of vertebrate retinal ganglion cell genesis.