Overexpression of S-adenosylmethionine decarboxylase (SAMDC) in Xenopus embryos activates maternal program of apoptosis

In Xenopus, injection of S-adenosylmethionine decarboxylase (SAMDC) mRNA into fertilized eggs or2-cell stage embryos induces massive cell dissociation and embryo-lysis at the early gastrula stage due toactivation of the maternal program of apoptosis. We injected SAMDC mRNA into only one of the animalside blastomeres of embryos at different stages of cleavage, and examined the timing of the onset of theapoptotic reaction. In the injection at 4- and 8-cell stages, a considerable number of embryos developed intotadpoles and in the injection at 16- and 32-cell stages, all the embryos became tadpoles, although tadpolesobtained were sometimes abnormal. However, using GFP as a lineage tracer, we found that descendant cellsof the blastomere injected with SAMDC mRNA at 8- to 32-cell stages are confined within the blastocoel atthe early gastrula stage and undergo apoptotic cell death within the blastocoel, in spite of the continueddevelopment of the injected embryos. These results indicate that cells overexpressed with SAMDC undergoapoptotic cell death consistently at the early gastrula stage, irrespective of the timing of the mRNA injection.We assume that apoptosis is executed in Xenopus early gastrulae as a "fail-safe" mechanism to eliminatephysiologically-severely damaged cells to save the rest of the embryo.

作 者： MASATAKE KAI CHIKARA KAITO HIROSHI FUKAMACHI TAKAYASU HIGO EIJI TA-KAYAMA HIROSHI HARA YOSHIKAZU OHYA KAZUEI IGARASHI KOICHIRO SHIOKAWA   作者單位： MASATAKE KAI,HIROSHI FUKAMACHI,KOICHIRO SHIOKAWA(Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan)

CHIKARA KAITO(Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan;Laboratory of Developmental Biochemistry, Graduate School of Pharmaceutical Sciences, Un)

TAKAYASU HIGO(Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan;Department of Basic Medical Sciences, The Institute of Medical Science, University of To)

EIJI TA-KAYAMA(Department of Parasitology, National Defense Medical College, Namiki 3-2, Tokorozawa, Saitama, 359-8543, Japan)

HIROSHI HARA(Medicinal Research Laboratories, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-cho, Kita-ku, Saitama 331-9530, Japan)

YOSHIKAZU OHYA(Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan)

KAZUEI IGARASHI(Faculty of Pharmaceutical Sciences, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan) 

刊 名： 細(xì)胞研究(英文版)  ISTIC SCI 英文刊名： CELL RESEARCH  年，卷(期)： 2003 13(3)  分類號： Q2  關(guān)鍵詞： SAMDC overexpression   maternal apoptosis program   processing-defective SAMDC mutant   MBT   fail-safe mechanism