Environmental and genetic modifiers of squint penetrance during zebrafish embryogenesis

Vincent Fleury, le 09-01-2007 à 15:13 : Je suis désolé de devoir insister : ouvrez vos yeux, ça n’a AUCUN sens d’invoquer la fonction d’un organe, si l’ensemble des modifications possibles d’un animal ne sont pas quelconques. L’influence de l’environnement sur le développement de UN animal est égal à ZERO, et l’influence sur les mutations est égale à ZERO. ZERO fois ZERO= ZERO.

Je trouve que ce sont les dires de VF qui ont de moins en moins de sens et que c’est leur influence qui devrait tendre vers zéro.

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Environmental and genetic modifiers of squint penetrance during zebrafish embryogenesis

Wuhong Pei, P. Huw Williams, Matthew D. Clark, Derek L. Stemple, , and Benjamin Feldman

Developmental Biology Volume 308, Issue 2, 15 August 2007, Pages 368-378

The Nodal-related subgroup of the TGFβ superfamily of secreted cytokines regulates the specification of the mesodermal and endodermal germ layers during gastrulation. Two Nodal-related proteins – Squint (Sqt) and Cyclops (Cyc) – are expressed during germ-layer specification in zebrafish. Genetic sqt mutant phenotypes have defined a variable requirement for zygotic Sqt, but not for maternal Sqt, in midline mesendoderm development. However a comparison of phenotypes arising from oocytes or zygotes injected with Sqt antisense morpholinos has suggested a novel requirement for maternal Sqt in dorsal specification. In this study we examined maternal–zygotic mutants for each of two sqt alleles and we also compared phenotypes of closely related zygotic and maternal–zygotic sqt mutants. Each of these approaches indicated there is no general requirement for maternal Sqt. To better understand the dispensability of maternal and zygotic Sqt, we sought out developmental contexts that more rigorously demand intact Sqt signalling. We found that sqt penetrance is influenced by genetic modifiers, by environmental temperature, by levels of residual Activin-like activity and by Heat-Shock Protein 90 (HSP90) activity. Therefore, Sqt may confer an evolutionary advantage by protecting early-stage embryos against detrimental interacting alleles and environmental challenges.

Keywords: TGFβ signaling; Gastrulation; Embryogenesis; Zebrafish