Lineage-specific segregation of maternal mRNA

用辣根过氧化物酶（HRP）和亲脂性示踪剂Dil细胞内显微注射的方法，研究了寡毛纲环节动物Tubifex胚胎D细胞系第二（2d）和第四（4d）微节的细胞谱系。2d产生四对双侧端细胞（N、O、P和Q），4d产生一对双侧M端细胞。由端细胞N-Q分化而来的胚带构成表皮细胞、腹神经索、外周神经元和背、腹刚毛囊。来自M端细胞的胚带几乎参与了所有的中胚层组织，即，环形和纵向肌肉，肾管，原始生殖细胞和体腔壁，包括血管;位于每个节段神经节中心的一些细胞也来自这些胚胎区域。碱性磷酸酶活性在第7、8节中胚层细胞中特异表达。结合Dillabeling的细胞消融实验表明，节段性的身份是在m-blast细胞诞生时确定的。这些结果证实了Penners（1924）的一些推论，但也揭示了几个需要纠正的重要问题。为了检查2d和4d是否遗传特定的母体信息，在完整的胚胎和2d和4d已经被消融的胚胎之间进行减法实验。到目前为止，还没有发现任何重要的分子。

The cell lineages of the second (2d) and fourth (4d) micromeres of the D-cell line of the oligochaete annelid Tubifex embryo were examined by means of intracellular microinjection of horseradish peroxidase (HRP) and a lipophilic tracer Dil. 2d produces four bilateral pairs of teloblasts (N,O,P and Q) , and 4d gives rise to a bilateral pair of M-teloblasts. The germ bands derived form teloblasts N-Q contribute to epidermal cells, ventral nerve cord, peripheral neurons and dorsal and ventral setal sacs. The germ bands derived from M-teloblasts contribute to nearly all of mesodernal tissues, viz., circular and longitudinal muscles, nephridia, primordial germ cells and coelomic walls including blood vessels ; a few cells located at the center of each segmental ganglion are also derived from these embryonic regions. Alkaline phosphatase activity was specifically expressed in mesodermal cells at the 7th and 8th segments. Cell ablation experiments in combination with Dillabeling suggested that segmental identity is determined at the birth of m-blast cells. These results confirm some of Penners' (1924) inference, but have uncovered several important points that should be corrected. To examine whether 2d and 4d inherit specific maternal messages, subtraction experiments were performed between intact embryos and those from which 2d and 4d had been ablated. To date, any significant molecules have not been found.