Involvement of a Basic Helix-Loop-Helix Gene BHLHE40 in Specification of Chicken Retinal Pigment Epithelium

Toshiki Kinuhata, Keita Sato, Tetsuya Bando, Taro Mito, Satoru Miyaishi, Tsutomu Nohno, Hideyo Ohuchi

Research output: Contribution to journalArticlepeer-review

Abstract

The first event of differentiation and morphogenesis in the optic vesicle (OV) is specification of the neural retina (NR) and retinal pigment epithelium (RPE), separating the inner and outer layers of the optic cup, respectively. Here, we focus on a basic helix-loop-helix gene, BHLHE40, which has been shown to be expressed by the developing RPE in mice and zebrafish. Firstly, we examined the expression pattern of BHLHE40 in the developing chicken eye primordia by in situ hybridization. Secondly, BHLHE40 overexpression was performed with in ovo electroporation and its effects on optic cup morphology and expression of NR and RPE marker genes were examined. Thirdly, we examined the expression pattern of BHLHE40 in LHX1-overexpressed optic cup. BHLHE40 expression emerged in a subset of cells of the OV at Hamburger and Hamilton stage 14 and became confined to the outer layer of the OV and the ciliary marginal zone of the retina by stage 17. BHLHE40 overexpression in the prospective NR resulted in ectopic induction of OTX2 and repression of VSX2. Conversely, BHLHE40 was repressed in the second NR after LHX1 overexpression. These results suggest that emergence of BHLHE40 expression in the OV is involved in initial RPE specification and that BHLHE40 plays a role in separation of the early OV domains by maintaining OTX2 expression and antagonizing an NR developmental program.

Original languageEnglish
Article number45
JournalJournal of Developmental Biology
Volume10
Issue number4
DOIs
Publication statusPublished - Dec 2022

Keywords

  • basic helix-loop-helix e40
  • BHLHE40
  • chicken
  • LHX1
  • LIM homeobox 1
  • neural retina
  • optic vesicle
  • retinal pigment epithelium
  • RPE

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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