Epigenetic and physiological alterations in zebrafish subjected to hypergravity

Abstract

Gravity is one of the most constant environmental factors across Earths evolution and all organisms are adapted to it. Consequently, spatial exploration has captured the interest in studying the biological changes that physiological alterations are caused by gravity. In the last two decades, epigenetics has explained how the environmental cues are able to altered gene functions in the organisms. Although many studies addressed gravity, the underlying biological and molecular mechanisms that are occurred in altered gravity for those epigenetics-related mechanisms, are mostly inexistent. The present study addressed the effects of hypergravity on development, behavior, gene expression, and most importantly, on the epigenetic changes in a world-wide animal model, the zebrafish (Danio rerio). To perform hypergravity experiments, a custom-centrifuge simulating the large diameter centrifuge (100 rpm [~] 3 g) were designed and zebrafish embryos were exposed during 5 days post fertilization (dpf). Results showed a significant decrease of survival at 2 dpf but not significance in the hatching rate. Physiological and morphological alterations including fish position, movement frequency and swimming behavior showed significant changes due to hypergravity. Epigenetic studies showed a significant hypermethylation of the genome of the zebrafish larvae subjected to 5 days of hypergravity. A downregulation of the gene expression of three epigenetic-related genes (dnmt1, dnmt3, and tet1), although not significant, were further observed. Taken altogether, gravity alterations affected biological responses including epigenetics in fish, providing a valuable roadmap of the putative hazards of living beyond Earth.