The Homeobox Gene Gsx2 Regulates the Self-Renewal and Differentiation of Neural Stem Cells and the Cell Fate of Postnatal Progenitors

The Genetic screened homeobox 2 (Gsx2) transcription factor is required for the development of olfactory bulb (OB) and striatal neurons, and for the regional specification of the embryonic telencephalon. Although Gsx2 is expressed abundantly by progenitor cells in the ventral telencephalon, its precise function in the generation of neurons from neural stem cells (NSCs) is not clear. Similarly, the role of Gsx2 in regulating the self-renewal and multipotentiality of NSCs has been little explored. Using retroviral vectors to express Gsx2, we have studied the effect of Gsx2 on the growth of NSCs isolated from the OB and ganglionic eminences (GE), as well as its influence on the proliferation and cell fate of progenitors in the postnatal mouse OB. Expression of Gsx2 reduces proliferation and the self-renewal capacity of NSCs, without significantly affecting cell death. Furthermore, Gsx2 overexpression decreases the differentiation of NSCs into neurons and glia, and it maintains the cells that do not differentiate as cycling progenitors. These effects were stronger in GESCs than in OBSCs, indicating that the actions of Gsx2 are cell-dependent. In vivo, Gsx2 produces a decrease in the number of Pax6+ cells and doublecortin+ neuroblasts, and an increase in Olig2+ cells. In summary, our findings show that Gsx2 inhibits the ability of NSCs to proliferate and self-renew, as well as the capacity of NSC-derived progenitors to differentiate, suggesting that this transcription factor regulates the quiescent and undifferentiated state of NSCs and progenitors. Furthermore, our data indicate that Gsx2 negatively regulates neurogenesis from postnatal progenitor cells.

遗传筛选同源盒2（Genetic screened homeobox 2，Gsx2）转录因子对于嗅球（olfactory bulb，OB）与纹状体神经元的发育，以及胚胎端脑的区域特化具有不可或缺的作用。尽管Gsx2在腹侧端脑的祖细胞中高表达，但其在神经干细胞（neural stem cells，NSCs）向神经元分化过程中的具体功能仍未阐明。同样，Gsx2在调控NSCs自我更新与多能性方面的作用也鲜有探索。
本研究通过逆转录病毒载体表达Gsx2，探究了其对分离自嗅球与神经节隆起（ganglionic eminences，GE）的NSCs生长的影响，以及对出生后小鼠嗅球内祖细胞增殖与细胞命运的调控作用。实验结果显示，Gsx2的表达可降低NSCs的增殖能力与自我更新潜能，且不会显著影响细胞死亡。进一步研究发现，Gsx2过表达会抑制NSCs向神经元与胶质细胞的分化，并维持未分化细胞处于增殖祖细胞状态。相较于嗅球来源干细胞（olfactory bulb-derived stem cells，OBSCs），上述效应在神经节隆起来源干细胞（ganglionic eminences-derived stem cells，GESCs）中更为显著，表明Gsx2的调控作用具有细胞依赖性。
在体内实验中，Gsx2可减少Pax6阳性细胞与双皮质素阳性成神经细胞的数量，并增加Olig2阳性细胞的占比。综上，本研究结果表明，Gsx2可抑制NSCs的增殖与自我更新能力，同时削弱NSCs来源祖细胞的分化潜能，提示该转录因子可调控NSCs与祖细胞的静息未分化状态。此外，本研究数据证实Gsx2对出生后祖细胞的神经发生过程具有负调控作用。