GSK3 Temporally Regulates Neurogenin 2 Proneural Activity in the Neocortex
GSK3 Temporally Regulates Neurogenin 2 Proneural Activity in the Neocortex
复制标题
DOI：
10.1523/jneurosci.1309-12.2012
复制
发表时间：
2012-06-06
影响因子：
5.3
通讯作者：
Schuurmans, Carol
中科院分区：
文献类型：
--
作者：
Li, Saiqun;Mattar, Pierre;Schuurmans, Carol
新皮质由六个神经元层组成，这些神经元层按定义的时间顺序生成。虽然已知外在和内在线索可以调节新皮质神经元的顺序产生，但人们对这些因素如何相互作用和以协调的方式发挥作用却知之甚少。原神经基因 Neurog2 在整个皮质发生过程中在祖细胞中表达，但仅需要指定早期出生的深层神经元身份。在这里，我们研究了小鼠新皮质发育过程中一般神经元分化和特别是 Neurog2 功能如何受到时间控制。我们发现 Neurog2 前神经活性在皮质生成晚期下降，这与其被 GSK3 激酶磷酸化相关。因此，受经典 Wnt 信号传导负调控的 GSK3 活性随着发育时间的推移而增加，而 Wnt 信号传导相应减少。当异位激活时，GSK3 抑制培养细胞中 Neurog2 介导的转录和体内 Neurog2 原神经活性。相反，GSK3 活性的降低促进后期皮质祖细胞的早熟分化，而不影响层状命运规范。从机制上讲，我们发现 GSK3 通过影响二聚化伴侣的选择、促进与 E47 (Tcfe2a) 的异二聚体相互作用来抑制 Neurog2 活性，而不是在 GSK3 活性水平较低时形成 Neurog2-Neurog2 同二聚体。在功能水平上，与 Neurog2-Neurog2 同二聚体相比，Neurog2-E47 异二聚体反式激活神经元分化基因的能力在体外和体内均较低。因此，我们得出结论，GSK3 对 Neurog2-E47 异二聚化的时间调节是协调小鼠新皮质神经发生的时间和节奏的神经元分化“时钟”的核心组成部分。
The neocortex is comprised of six neuronal layers that are generated in a defined temporal sequence. While extrinsic and intrinsic cues are known to regulate the sequential production of neocortical neurons, how these factors interact and function in a coordinated manner is poorly understood. The proneural gene Neurog2 is expressed in progenitors throughout corticogenesis, but is only required to specify early-born, deep-layer neuronal identities. Here, we examined how neuronal differentiation in general and Neurog2 function in particular are temporally controlled during murine neocortical development. We found that Neurog2 proneural activity declines in late corticogenesis, correlating with its phosphorylation by GSK3 kinase. Accordingly, GSK3 activity, which is negatively regulated by canonical Wnt signaling, increases over developmental time, while Wnt signaling correspondingly decreases. When ectopically activated, GSK3 inhibits Neurog2-mediated transcription in cultured cells and Neurog2 proneural activities in vivo. Conversely, a reduction in GSK3 activity promotes the precocious differentiation of later stage cortical progenitors without influencing laminar fate specification. Mechanistically, we show that GSK3 suppresses Neurog2 activity by influencing its choice of dimerization partner, promoting heterodimeric interactions with E47 (Tcfe2a), as opposed to Neurog2-Neurog2 homodimer formation, which occurs when GSK3 activity levels are low. At the functional level, Neurog2-E47 heterodimers have a reduced ability to transactivate neuronal differentiation genes compared with Neurog2-Neurog2 homodimers, both in vitro and in vivo. We thus conclude that the temporal regulation of Neurog2-E47 heterodimerization by GSK3 is a central component of the neuronal differentiation "clock" that coordinates the timing and tempo of neocortical neurogenesis in mouse.