Lineage-specific segregation of maternal mRNA

用辣根过氧化物酶(HRP)和亲脂性示踪剂Dil细胞内微量注射的方法，观察了寡毛类环节动物Tubifex胚胎D细胞系第二(2d)和第四(4d)微粒的细胞系。2D产生四对双侧成端细胞(N、O、P和Q)，4d产生一对双侧M-成端细胞。由N-Q细胞分化而来的生殖带主要分布于表皮细胞、腹侧神经索、外周神经元以及背侧和腹侧的绒毛囊。几乎所有的中胚层组织，即环行肌、纵行肌、肾、原始生殖细胞和包括血管在内的体腔壁，都有来自M-端成体细胞的生殖带；位于每个节段神经节中心的少数细胞也来自这些胚区。碱性磷酸酶活性在第7和第8节的中胚层细胞中特异表达。结合狄拉贝林的细胞消融实验表明，节段性同一性是在m-BLAST细胞诞生时决定的。这些结果证实了Penners(1924)的一些推论，但也揭示了几个应该纠正的重要观点。为了检验2d和4d是否遗传了特定的母体信息，对完整的胚胎和2d和4d被切除的胚胎进行了减法实验。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.