Laboratory for Cell Asymmetry, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.
Dev Biol. 2010 Nov 1;347(1):9-23. doi: 10.1016/j.ydbio.2010.06.029. Epub 2010 Jul 1.
Asymmetric cell division generates two daughter cells of differential gene expression and/or cell shape. Drosophila neuroblasts undergo typical asymmetric divisions with regard to both features; this is achieved by asymmetric segregation of cell fate determinants (such as Prospero) and also by asymmetric spindle formation. The loss of genes involved in these individual asymmetric processes has revealed the roles of each asymmetric feature in neurogenesis, yet little is known about the fate of the neuroblast progeny when asymmetric processes are blocked and the cells divide symmetrically. We genetically created such neuroblasts, and found that in embryos, they were initially mitotic and then gradually differentiated into neurons, frequently forming a clone of cells homogeneous in temporal identity. By contrast, larval neuroblasts with the same genotype continued to proliferate without differentiation. Our results indicate that asymmetric divisions govern lineage length and progeny fate, consequently generating neural diversity, while the progeny fate of symmetrically dividing neuroblasts depends on developmental stages, presumably reflecting differential activities of Prospero in the nucleus.
不对称细胞分裂会产生两个具有不同基因表达和/或细胞形态的子细胞。果蝇神经母细胞在这两个方面都经历典型的不对称分裂；这是通过细胞命运决定因素（如 Prospero）的不对称分配以及不对称纺锤体的形成来实现的。参与这些单个不对称过程的基因的缺失揭示了每个不对称特征在神经发生中的作用，但当不对称过程被阻断并且细胞对称分裂时，神经母细胞后代的命运知之甚少。我们通过遗传方法创造了这样的神经母细胞，并发现它们在胚胎中最初是有丝分裂的，然后逐渐分化为神经元，经常形成具有相同时间特征的细胞克隆。相比之下，具有相同基因型的幼虫神经母细胞继续增殖而不分化。我们的结果表明，不对称分裂控制着谱系长度和后代命运，从而产生神经多样性，而对称分裂的神经母细胞的后代命运取决于发育阶段，这可能反映了 Prospero 在核内的不同活性。
