Weigmann K, Lehner C F
Friedrich-Miescher-Laboratorium, Max-Planck-Gesellschaft, Tübingen, FRG.
Development. 1995 Nov;121(11):3713-21. doi: 10.1242/dev.121.11.3713.
The correct specification of defined neurons in the Drosophila central nervous system is dependent on even-skipped. During CNS development, even-skipped expression starts in the ganglion mother cell resulting from the first asymmetric division of neuroblast NB 1-1. This first division of NB 1-1 (and of the other early neuroblasts as well) is temporally controlled by the transcriptional regulation of string expression, which we have manipulated experimentally, even-skipped expression still occurs if the first neuroblast division is delayed, but not if the division is prohibited. Moreover, even-skipped expression is also dependent on progression through S phase which follows immediately after the first division. However, cytokinesis during the first NB division is not required for even-skipped expression as revealed by observations in pebble mutant embryos. Our results demonstrate therefore that even-skipped expression is coupled to cell cycle progression, presumably in order to prevent a premature activation of expression by a positive regulator which is produced already in the neuroblast during G2 and segregated asymmetrically into the ganglion mother cell during mitosis.
果蝇中枢神经系统中特定神经元的正确特化依赖于偶数跳动基因（even-skipped）。在中枢神经系统发育过程中，偶数跳动基因的表达始于神经母细胞NB 1-1第一次不对称分裂产生的神经节母细胞。NB 1-1的这第一次分裂（以及其他早期神经母细胞的分裂）在时间上受String基因表达的转录调控，我们通过实验对其进行了操控。如果第一个神经母细胞分裂延迟，偶数跳动基因仍会表达，但如果分裂被阻止则不会表达。此外，偶数跳动基因的表达还依赖于紧随第一次分裂后的S期进程。然而，正如在卵石（pebble）突变胚胎中的观察结果所示，第一次NB分裂期间的胞质分裂对于偶数跳动基因的表达并非必需。因此，我们的结果表明，偶数跳动基因的表达与细胞周期进程相关联，推测这是为了防止一种在G2期于神经母细胞中已经产生并在有丝分裂期间不对称分离到神经节母细胞中的正向调节因子过早激活基因表达。
