両生類の生活環に対する重力影響:初期発生、形態形成や変態の形態学的および分子生物学的解析

This study attempts to investigate abnormal Programmed Cell Death (PCD) and abnormal gene expression induced under high gravity conditions. Uncleaved Xenopus laevis eggs at 10 and 20 min after insemination, and embryos at 2 cell stage were raised at 2 G and 5 G. Controls were raised in normal gravity. PCD for body surface and inner structures of hatched tadpoles was scored using the TUNEL staining method, and gene expression was analyzed by whole-mount in situ hybridization when eggs and embryos reached tail-bud embryos. The results showed that: (1) High gravity retarded the development of eggs and embryos and induced microcephaly and microphthalmia. (2) The number of dying cells in the skin of tadpoles developed from treated eggs and cell 2 stage embryos was greater at 2 G, but less at 5 G, compared to controls. The number of PCD in head epidermis of tadpoles developed from treated eggs and embryos was higher at 2 G than in controls, but the same as controls at 5 G. Brain PCD was found to be the same at 2 G, but higher at 5 G than for controls. (3) High gravity strongly suppressed the expression of the two genes, XAG1 (regulating cement gland formation) and Xotx2 (involved in forebrain and eye development). These findings suggest that high gravity induces abnormal PCD and suppresses gene functions essential for head and brain development, leading to retardation and various morphological abnormalities.
資料番号: AA0048095063