Analysis of Head-Defects Caused by Hypergravity in Early Xenopus Embryos

Abstract

Xenopus embryos raised under hypergravity conditions develop a variety of abnormalities. Among them, head defects such as microcephaly and cyclopia are the most common phenotypes. Higher hypergravity (i.e., 5G) has been shown to cause more head defects in embryos than a lower one (i.e., 2G). However, the degree of head defects in embryos has not been studied quantitatively. In this study, we applied the Dorsoanterior Index (DAI) to quantitatively evaluate the degree of head defects caused by hypergravity. Moreover, we investigated the molecular mechanisms of head defects. Because Wnt signaling plays a crucial role in dorsal specification of embryos required for proper head formation, we examined the activity of endogenous Wnt signaling by monitoring direct Wnt target gene expression and found that the expression of these genes was reduced in hypergravity-treated embryos. This suggests that inhibition of Wnt signaling may be one of the mechanisms of hypergravity-derived head defects in early Xenopus embryos.