Elevated expression of human bHLH factor ATOH7 accelerates cell cycle progression of progenitors and enhances production of avian retinal ganglion cells

Xiang-Mei Zhang,Ronald Tang,Takao Hashimoto,Xian-Jie Yang

doi:10.1038/s41598-018-25188-z

Xiang-Mei Zhang, Ronald Tang + Show 2 more

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https://doi.org/10.1038/s41598-018-25188-z

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Abstract

The production of vertebrate retinal projection neurons, retinal ganglion cells (RGCs), is regulated by cell-intrinsic determinants and cell-to-cell signaling events. The basic-helix-loop-helix (bHLH) protein Atoh7 is a key neurogenic transcription factor required for RGC development. Here, we investigate whether manipulating human ATOH7 expression among uncommitted progenitors can promote RGC fate specification and thus be used as a strategy to enhance RGC genesis. Using the chicken retina as a model, we show that cell autonomous expression of ATOH7 is sufficient to induce precocious RGC formation and expansion of the neurogenic territory. ATOH7 overexpression among neurogenic progenitors significantly enhances RGC production at the expense of reducing the progenitor pool. Furthermore, forced expression of ATOH7 leads to a minor increase of cone photoreceptors. We provide evidence that elevating ATOH7 levels accelerates cell cycle progression from S to M phase and promotes cell cycle exit. We also show that ATOH7-induced ectopic RGCs often exhibit aberrant axonal projection patterns and are correlated with increased cell death during the period of retinotectal connections. These results demonstrate the high potency of human ATOH7 in promoting early retinogenesis and specifying the RGC differentiation program, thus providing insight for manipulating RGC production from stem cell-derived retinal organoids.

Highlights

Development of the vertebrate retina follows an evolutionarily conserved chronological order with retinal ganglion cells (RGCs) among the earliest born postmitotic neurons[1,2]
At the onset of the chicken retinogenesis at Hamburger and Hamilton (HH) stage 1545, the central retina showed the initial emergence of a few Atoh7expressing progenitors
Our results show that ectopic expression of human ATOH7 leads to precocious neurogenesis and expansion of the neurogenic territory to the peripheral retina

Summary

Introduction

Development of the vertebrate retina follows an evolutionarily conserved chronological order with retinal ganglion cells (RGCs) among the earliest born postmitotic neurons[1,2]. It has been shown that mouse Atoh[7] expressed from the bHLH factor Neurod[1] gene locus can cause switches from amacrine and photoreceptor identities to RGC characteristics[42], supporting that Atoh[7] can promote and initiate RGC differentiation program in postmitotic neurons. To enhance our current understanding of neurogenic mechanisms, especially the role of human ATOH7 in development and pathogenesis, we have used the developing chicken retina as an in vivo model system, which permits easy access during the early stages of retinogenesis, to evaluate whether human ATOH7 can impact the behavior and cell fate decisions of uncommitted retinal progenitors. We provide evidence that elevating ATOH7 expression accelerates cell cycle progression and promotes cell cycle exit, leading to enhanced RGC production These findings support a role of ATOH7 in RGC fate determination and suggest a useful strategy to manipulate RGC production in human pluripotent stem cell-derived retinal organoids

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