Subterranean Fishes of the World

5636

2022

AIM 2022

40

Now published in Development

The vertebrate retinas originate from a specific anlage in the anterior neural plate called the eyefield. Its identity is conferred by a set of “eye transcription factors”, whose combinatorial expression has been overlooked. Here, we use the dimorphic teleost Astyanax mexicanus, which develops proper eyes in the wild type and smaller colobomatous eyes in the blind cavefish embryos, to unravel the molecular anatomy of the eyefield and its variations within a species. Using a series of markers (Rx3, Pax6a, CxCr4b, Zic1, Lhx2, Emx3, Nkx2.1a), we draw a comparative 3D expression map at the end of gastrulation/onset of neurulation, which highlights hyper-regionalization of the eyefield into sub-territories of distinct sizes, shapes, cell identities and combinatorial gene expression levels along the three body axes. All these features show significant variations in the cavefish natural mutant. We also discover sub-domains within the prospective telencephalon and characterize cell identities at the frontiers of the eyefield. We propose putative fates for some of the characterized eyefield subdivisions, and suggest the existence of a trade-off between some subdivisions in the two Astyanax morphs at microevolutionary scale.

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