PDK1 Regulates Transition Period of Apical Progenitors to Basal Progenitors by Controlling Asymmetric Cell Division.

The six-layered neocortex consists of diverse neuron subtypes. Deeper-layer neurons originate from apical progenitors (APs), while upper-layer neurons are mainly produced by basal progenitors (BPs), which are derivatives of APs. As development proceeds, an AP generates two daughter cells that comprise an AP and a deeper-layer neuron or a BP. How the transition of APs to BPs is spatiotemporally regulated is a fundamental question. Here, we report that conditional deletion of phoshpoinositide-dependent protein kinase 1 (PDK1) in mouse developing cortex achieved by crossing Emx1Cre line with Pdk1fl/fl leads to a delayed transition of APs to BPs and subsequently causes an increased output of deeper-layer neurons. We demonstrate that PDK1 is involved in the modulation of the complex and further regulates the asymmetric cell division (ACD). We also find Hes1, a downstream effecter of Notch signal pathway is obviously upregulated. Knockdown of Hes1 or treatment with Notch signal inhibitor DAPT recovers the ACD defect in the Pdk1 cKO. Thus, we have identified a novel function of PDK1 in controlling the transition of APs to BPs.

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