Hypergravity Specifically Affects Anterior Head Formation in Early Xenopus Embryos

Xenopus embryos raised under conditions of hypergravity develop various abnormalities, including head defects such as microcephaly and cyclopis. However, it is unknown which region of the head is most sensitive to hypergravity, and whether regions behind the midbrain are affected by hypergravity. In this study, we investigated the effects of hypergravity on Xag , Xotx2 , En2 , Krox20 , and HoxB9 expression by whole-mount in situ hybridization. Double staining with Xag and Xotx2 revealed that Xotx2 expression was dramatically suppressed in embryos exposed to 5 G ; Xag expression was also affected, but to a lesser extent. Furthermore, En2 expression was also affected by hypergravity. A detailed examination by double staining with Xotx2 and En2 showed that although Xotx2 expression was strongly suppressed in embryos exposed to 5 G , the region expressing En2 was only slightly smaller. Lastly, Krox20 or HoxB9 expression was unaffected by hypergravity. These results suggest that formation of the anterior head region, including the eyes, forebrain, and midbrain, in Xenopus embryos is sensitive to hypergravity, while the posterior regions (i.e., behind the hindbrain) are unaffected by hypergravity. doi:

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