| Co-Investigator(Kenkyū-buntansha) |
MATSUMOTO Mitsuharu Kagoshima University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (30157383)
AOKI Takayoshi Kagoshima University, Faculty of Agriculture, Professor, 農学部, 教授 (70034460)
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| Research Abstract |
Ovalbumin, which is the major albumen protein having carbohydrate and phosphate residues, belongs to the serine protease inhibitor superfamily. However, ovalbumin is not inhibitory against proteases, and, therefore, its function remains uncertain except for a possible contribution as a nutrient source. We reported previously that ovalbumin molecules were transported from albumen to the embryo via egg yolk, amniotic fluid, serum etc, without degradation, and distributed in various organs including the central nervous system, while these molecules undergo changes in secondary conformation and attain a heat-stable state (this state of molecules will be called 'HS-ovalbumin'). Here we showed that HS-ovalbumin is distinguishable from the known heat-stable molecular form named S-ovalbumin by a presently prepared monoclonal antibody and that HS-ovalbumin arises from its native form (N-ovalbumin) in developing eggs. We also established in vitro culture conditions, under which embryos isolated from eggs at and after stage 4 of embryogenesis could be successfully cultured for at least 24 h. When the remnant fractions of endogenous ovalbumin was neutralized by using a polyclonal antibody, the isolated embryos could not grow normally, being particularly irregular in the brain tissue, which hardly undergo the neural tube closure occurring in normal embryos at stage 9. The embryos were rescued from the aberration by adding an excess amount of ovalbumin to the medium at an early period of culture. HS-ovalbumin showed a higher rescue rate than the N-and S-counterparts. Our findings demonstrated that ovalbumin is indispensable to, and probably plays a crucial role in, the embryonic organogenesis.
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