| 1 | Overexpression of S-adenosylmethionine decarboxylase(SAMDC)in Xeno-pus embryos activates maternal program of apoptosis as a 'fail-safe'mechanism of early embryogenesis显示文摘In Xenopus, injection of S-adenosylmethionine decarboxylase (SAMDC) mRNA into fertilized eggs or 2-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 continued development of the injected embryos. These results indicate that cells overexpressed with SAMDC undergo apoptotic 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 'fall-safe' mechanism to eliminate physiologically-severely damaged cells to save the rest of the embryo. | MASATAKEKAI CHIKARAKAITO HIROSHIFUKAMACHI TAKAYASUHIGO EIJI TAKAYAMA HIROSHI HARA YOSHIKAZU OHYA KAZUEI IGARASHI KOICHIRO SHIOKAWA | 2003 | Cell Research2003，13，3： | 4 |
| 2 | A developmental biological study of aldolase gene expression in Xenopus laevis显示文摘We cloned cDNAs for Xenopus aldolases A, B and C. These three aldolase genes are localized on different chromosomes as a single copy gene. In the adult, the aldolase A gene is expressed extensively in muscle tissues, whereas the aldolase B gene is expressed strongly in kidney, liver, stomach and intestine, while the aldolase C gene is expressed in brain, heart and ovary. In oocytes aldolase A and C mRNAs, but not aldolase B mRNA, are extensively transcribed. Thus, aldolase A and C mRNAs, but not B mRNA, occur abundantly in eggs as maternal mRNAs, and strong expression of aldolase B mRNA is seen only after the late neurula stage. We conclude that aldolase A and C mRNAs are major aldolase mRNAs in early stages of Xenopus embryogenesis which proceeds utilizing yolk as the only energy source, aldolase B mRNA, on the other hand, is expressed only later in development in tissues which are required for dietary fructose metabolism.We also isolated the Xenopus aldolase C genomic gene (ca. 12 kb) and found that its promoter (ca. 2 kb)contains regions necessary for tissue-specific expression and also a GC rich region which is essential for basal transcriptional activity. | KOICHIRO SHIOKAWA, ERI KAJITA, HIROSHI HARA, HITOMI YATSUKI, KATSUJI HORI1 Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, TheUniversity of Tokyo, Hongo 7-3-1, Bunkyo ku, Tokyo 113-0033, Japan 2Medical Re | 2002 | Cell Research2002，12，2： | 0 |
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