CaveMum · The role of embryonic metabolism under maternal control in phenotypic evolution of blind cavefish

Animal development is initially directed by maternal products deposited in the egg, entirely controlling early embryogenesis, including key patterning events, before the maternal-to-zygotic transition (MZT) and zygotic genome activation. Despite differences in maternal programmes between species, the role of maternal factors in morphological evolution remains largely unexplored.This project aims to address this question using Astyanax mexicanus – a fish species with sighted river-dwelling (SF) and blind cave-adapted (CF) morphs that have rapidly and extensively diverged in morphology, physiology and behaviour. CF and SF egg transcriptomes display strong maternal signatures linked to differences in gastrulation and cavefish sensory phenotypes. The host laboratory discovered that divergence between maternal programmes primarily involves genes with metabolism-related functions. Thus, variation in embryonic metabolism and processes it influences may constitute an important mechanism of developmental evolution. To address this hypothesis, I propose to first characterise the aspects of metabolism under divergent maternal control to identify candidate genes for functional analysis. Second, I will employ transcriptome editing and chemical treatments to examine the function of the candidate genes in cavefish embryogenesis, and the phenotypic outcomes will be characterised to link metabolic and phenotypic variation. Finally, I will test the hypothesis that morph-specific aspects of embryonic metabolism may influence the timing, dynamics and extent of the essential transcriptome reprogramming event during embryo development – MZT. Altogether, this innovative, timely and highly integrative study will shed new light on the functional importance and mechanisms of maternal control and embryonic metabolism in the phenotypic evolution of cavefish and, more broadly, vertebrates.