Differential gene expression in tthat occurs during the conversion from symmetrically ddividing neuroepithelial stem cells into asymmetricallly dividing neural progenitos

果蝇幼虫视叶外增殖中心(OPC)的神经上皮构成视神经元的原基。神经前体在分化成神经母细胞(NBS)之前甚至有时甚至在分化成神经母细胞(NBS)之后经历巨大的扩张，最终产生视神经元。然而，还没有一项研究对这种扩张是如何发生的提供详细的解释。在这里，我们展示了位于OPC核心神经上皮区边缘的神经上皮细胞(NE)在G1期单独转化为NBS。随着细胞周期从G1期进入S期，这一转变就完成了。在这个G1期，曾经是NE的细胞开始致力于分化，改变其细胞时相控制，并通过重组连接它与其他NE细胞的贴壁连接将其形态从柱状改变为液滴状，最终成为NB并开始不对称分裂。

The neuroepithelium of the outer proliferating center (OPC) of the Drosophila larval optic lobe comprises the primordia for optic neurons. The neural precursors undergo enormous expansion probably before and sometimes even after differentiating into neuroblasts (NBs), which ultimately produce optic neurons. However, no study has yet provided a detailed explanation of how this expansion occurs. Here we show that neuroepithelial cells (NEs) at the margin of the core neuroepithelial region of the OPC convert individually into NBs during G1 phase. As the cell cycle progresses from G1 to the S phase, the transition is completed. During this G1 period, a cell that used to be an NE becomes committed to differentiate, alters its cell phase control, and changes its morphology from a columnar to a drop-like shape by reorganizing the adherens junctions that had linked it to other NE cells, to finally become an NB and commence asymmetric division.