Perturbation of oocyte meiotic division by hypergravity in Caenorhabditis elegans

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We identified the aspect(s) of growth and development in the life cycle that are affected by hypergravity using an experimental model animal Caenorhabditis elegans. More than 100 G hypergravity decreased the hatching (survival) rate of eggs laid by adult hermaphrodites but had little effect on the brood size. Polar bodies were not excluded in the dead eggs that had been laid under hypergravity. In addition, hypergravity caused abnormal distribution of PAR2 protein that regulates polarization of the anterior-posterior axis. However, when the meiotic divisions following fertilization were allowed to take place at 1 G, after which the gravity was raised to 200 G, the resulting embryos developed normally and grew to adulthood. When adult hermaphrodites cultured at 100 G were transferred to 1 G, the fertilized eggs after the shift developed normally and their hatching rate recovered completely. In addition, at 100 G, the oocytes matured normally, as they showed activation of a MAP kinase MPK1. These results suggest that hypergravity affects a reproductive process, namely, oocyte meiotic division for exclusion of polar bodies and the anterior-posterior polarization, that require meiotic-specific cytoskeletal systems shortly after fertilization, in the C. elegans life cycle.