Conference Paper
Impact of maternal factors during evolution of gastrulation and forebrain morphogenesis in Astyanax mexicanus
Leclercq, J., Torres-Paz, J. and Rétaux, S.
Record Number:
4286
Year:
2019
Journal:
AIM 2019
Pages:
38
Abstract:
The central nervous system of vertebrates (including the retina part of the eyes) is determined
and patterned early during development when the neural plate is induced. This event occurs at
the end of gastrulation, by signals coming from underlying midline signaling centers: the
prechordal plate anteriorly and the notochord posteriorly. Both prechordal plate and notochordal
cells derive from the primary dorsal organizer (the Shield in teleost fishes) that is set by
asymmetric localization of maternal factors in the egg. We thus examined the possibility that
maternal determinants might be involved in the morphological evolution of the cavefish forebrain,
including its defective eye. We found significant variations, between surface fish and cavefish
embryos, during the formation of the shield and during the process of gastrulation, which might
have a major impact in later forebrain morphogenesis in cavefish. In particular, the expression of
the Wnt pathway inhibitor Dkk1b was significantly different in the Shield and prechordal plate
between the two eco-morphotypes. We then generated reciprocal F1 hybrids by crossing a male
from one morph with a female from the other morph, to uncover potential maternal effects in gene
regulation during gastrulation. Strikingly, the expression of organizer genes in F1 hybrids was
systematically the same as in the mother morphotype. These results highlight that maternal effect
genes are involved in the evolution of gastrulation between surface and cavefishes. Two
candidate genes, Vsx1 and Oep, whose mRNA levels were found significantly reduced in cavefish
fertilized eggs in RT-qPCR experiments (0.40 and 0.57 fold vs surface fish, respectively), were
tested in rescue experiments. However, injection of Vsx1 or Oep mRNA in one cell stage cavefish
embryos did not affect the Dkk1b expression pattern. Transcriptomic analysis is ongoing to
identify a larger set of maternal genes at work in this process.
Times Cited:
1
Conference Name:
Astyanax Interrnational Meeting
Relevent Species: