Handed asymmetry, handedness reversal and mechanisms of cell fate determination in nematode embryos.
Handed asymmetry, handedness reversal and mechanisms of cell fate determination in nematode embryos.
复制标题
线虫胚胎中手性不对称、手性逆转和细胞命运决定机制。
DOI：
10.1002/9780470514160.ch9
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Kershaw,D
中科院分区：
文献类型：
--
作者：
Wood,WB;Kershaw,D
秀丽线虫（decaenorhabditis eleganes）的胚胎表现出左右不对称和不变的手性。胚胎细胞谱系是不对称的：虽然动物通常是两侧对称的，只有少数左右不对称，但它的许多对侧类似细胞通过胚胎两侧的不同谱系产生。幼虫和成虫也表现出左右不对称，惯用手性通常是不变的。在暴露于诱变剂甲磺酸乙酯的成虫后代中，以及在早期卵裂中用几丁质酶破坏蛋壳的胚胎发育的动物中，具有相反手性的动物的频率增加。胚胎手性的逆转是在6细胞阶段通过显微操作直接完成的，结果是镜像，但其他正常发育成健康、可育的动物，所有通常的左右不对称都被逆转了。这表明：(1)6细胞胚胎中细胞位置的手性决定了整个发育过程中的手性；(2)在这一阶段，右侧的一对前卵裂球与左侧的一对相等；(3)动物两侧直系同源细胞命运的广泛差异必须由细胞相互作用决定，其中大多数可能发生在胚胎发生的早期，并且似乎在广泛分化的线虫物种中已经保守。
Embryos of the nematodeCaenorhabditis elegansexhibit left‐right asymmetry with an invariant handedness. The embryonic cell lineage is asymmetrical: although the animal is generally bilaterally symmetrical with only a few left‐right asymmetries, many of its contralaterally analogous cells arise via different lineages on the two sides of the embryo. Larvae and adults also exhibit left‐right asymmetries with a handedness that is normally invariant. The frequency of animals with opposite handedness was increased among the progeny of adults exposed to the mutagen ethyl methanesulphonate and among animals that developed from embryos treated in early cleavage with chitinase to destroy the egg shell. Reversal of embryonic handedness was accomplished directly by micromanipulation at the 6‐cell stage, resulting in mirror‐image but otherwise normal development into healthy, fertile animals with all the usual left‐right asymmetries reversed. This demonstrates that (1) the handedness of cell positions in the 6‐cell embryo dictates handedness throughout development; (2) at this stage the pair of anterior blastomeres on the right is equivalent to the pair on the left; and (3) the extensive differences in fates of lineally homologous cells on the two sides of the animal must be dictated by cellular interactions, most of which are likely to occur early in embryogenesis and appear to have been conserved in widely diverged nematode species.