Cameron R A, Fraser S E, Britten R J, Davidson E H
Division of Biology, California Institute of Technology, Pasadena 91125.
Dev Biol. 1990 Jan;137(1):77-85. doi: 10.1016/0012-1606(90)90009-8.
A specific set of founder cells uniquely gives rise to the oral and aboral ectoderms in the regularly developing sea urchin Strongylocentrotus purpuratus. We showed earlier that the polar No and Na (animal oral and animal aboral) blastomeres are specified by third cleavage, while the respective oral and aboral lineage contributions of the left and right NL (animal lateral) blastomeres have not yet segregated from one another at third cleavage. Here we demonstrate by iontophoretic injection of lysyl rhodamine dextran lineage tracer that segregation of oral vs aboral cell fates in the lineages of the NL blastomeres has still not occurred by fourth cleavage, but at fifth cleavage there arise from the NL sublineages founder cells whose progeny contribute exclusively to the aboral ectoderm. The sister cells of these fifth cleavage blastomeres are founder cells that contribute exclusively to oral structures. The aboral ectoderm tracts to which NL derivatives give rise occupy lateral regions of the anterior aboral ectoderm, while the oral structures deriving from the NL blastomeres are the lateral sectors of the ciliated bands. The cells of the ciliated bands do not express aboral ectoderm markers and are considered to constitute the border of the oral region. With these new findings we complete our knowledge of the origins, identities, and fates of the 11 founder cells, the progeny of which exclusively give rise to the aboral ectoderm, and of the 5 founder cells, the progeny of which exclusively produce the oral ectoderm and its derivatives.
在正常发育的紫海胆中，一组特定的原始细胞独特地产生口侧和反口侧外胚层。我们之前表明，极No和Na（动物口侧和动物反口侧）卵裂球在第三次卵裂时被指定，而左右NL（动物侧）卵裂球各自对口侧和反口侧谱系的贡献在第三次卵裂时尚未彼此分离。在这里，我们通过离子电渗法注射赖氨罗丹明葡聚糖谱系示踪剂证明，NL卵裂球谱系中口侧与反口侧细胞命运的分离在第四次卵裂时仍未发生，但在第五次卵裂时，NL亚谱系产生了原始细胞，其后代专门贡献给反口侧外胚层。这些第五次卵裂卵裂球的姐妹细胞是专门贡献给口侧结构的原始细胞。NL衍生物产生的反口侧外胚层束占据前反口侧外胚层的外侧区域，而源自NL卵裂球的口侧结构是纤毛带的外侧部分。纤毛带的细胞不表达反口侧外胚层标记物，被认为构成口侧区域的边界。有了这些新发现，我们完善了对11个原始细胞的起源、身份和命运的认识，其后代专门产生反口侧外胚层，以及对5个原始细胞的认识，其后代专门产生口侧外胚层及其衍生物。
