Dong R, Jacobs J R
Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada.
Dev Biol. 1997 Oct 15;190(2):165-77. doi: 10.1006/dbio.1997.8688.
Drosophila embryos deficient for programmed cell death produce 9 midline glia (MG) in addition to the wild-type complement of 3.2 MG/segment. More than 3 of the supernumerary MG derive from the MGP (MG posterior) lineage and the remainder from the MGA/MGM (MG anterior and middle) lineage. There is one unidentified additional neuron in the mesectoderm of embryos deficient for apoptosis. The supernumerary MG are not diverted from other lineages nor do they arise from an altered pattern of mitosis. Instead, these MG appear to arise from a normally existing pool of 12 precursor cells, larger than anticipated by earlier studies. During normal development, MG survival is dependent upon signaling to the Drosophila EGF receptor. The persistence of supernumerary MG in embryos deficient for apoptosis does not alter the spatial pattern of Drosophila EGF receptor signaling. The number and position of MG which express genes dependent upon EGF receptor function, such as pointed or argos, are indistinguishable from wild type. Genes of the spitz group are required for Drosophila EGF receptor function. Surviving MG in spitz group/H99 double mutants continue to express genes characteristic of the MG, but the cells fail to differentiate into ensheathing glia and are displaced from the nerve cord.
缺乏程序性细胞死亡的果蝇胚胎除了每个体节有野生型的3.2个中线胶质细胞（MG）外，还产生9个中线胶质细胞。多余的中线胶质细胞中超过3个来源于MGP（MG后部）谱系，其余的来源于MGA/MGM（MG前部和中部）谱系。在缺乏凋亡的胚胎中胚层中有一个身份不明的额外神经元。多余的中线胶质细胞并非从其他谱系转移而来，也不是由有丝分裂模式改变产生的。相反，这些中线胶质细胞似乎来源于一个正常存在的12个前体细胞库，比早期研究所预期的要大。在正常发育过程中，中线胶质细胞的存活依赖于向果蝇表皮生长因子受体的信号传导。在缺乏凋亡的胚胎中多余中线胶质细胞的持续存在不会改变果蝇表皮生长因子受体信号传导的空间模式。表达依赖于表皮生长因子受体功能的基因（如pointed或argos）的中线胶质细胞的数量和位置与野生型没有区别。spitz组基因是果蝇表皮生长因子受体功能所必需的。在spitz组/H99双突变体中存活的中线胶质细胞继续表达中线胶质细胞特有的基因，但这些细胞无法分化为包被胶质细胞，并从神经索中移位。
