Loulier Karine, Lathia Justin D, Marthiens Veronique, Relucio Jenne, Mughal Mohamed R, Tang Sung-Chun, Coksaygan Turhan, Hall Peter E, Chigurupati Srinivasulu, Patton Bruce, Colognato Holly, Rao Mahendra S, Mattson Mark P, Haydar Tarik F, Ffrench-Constant Charles
Center for Neuroscience, Children's National Medical Center, Washington, D.C., United States of America.
PLoS Biol. 2009 Aug;7(8):e1000176. doi: 10.1371/journal.pbio.1000176. Epub 2009 Aug 18.
During embryogenesis, the neural stem cells (NSC) of the developing cerebral cortex are located in the ventricular zone (VZ) lining the cerebral ventricles. They exhibit apical and basal processes that contact the ventricular surface and the pial basement membrane, respectively. This unique architecture is important for VZ physical integrity and fate determination of NSC daughter cells. In addition, the shorter apical process is critical for interkinetic nuclear migration (INM), which enables VZ cell mitoses at the ventricular surface. Despite their importance, the mechanisms required for NSC adhesion to the ventricle are poorly understood. We have shown previously that one class of candidate adhesion molecules, laminins, are present in the ventricular region and that their integrin receptors are expressed by NSC. However, prior studies only demonstrate a role for their interaction in the attachment of the basal process to the overlying pial basement membrane. Here we use antibody-blocking and genetic experiments to reveal an additional and novel requirement for laminin/integrin interactions in apical process adhesion and NSC regulation. Transient abrogation of integrin binding and signalling using blocking antibodies to specifically target the ventricular region in utero results in abnormal INM and alterations in the orientation of NSC divisions. We found that these defects were also observed in laminin alpha2 deficient mice. More detailed analyses using a multidisciplinary approach to analyse stem cell behaviour by expression of fluorescent transgenes and multiphoton time-lapse imaging revealed that the transient embryonic disruption of laminin/integrin signalling at the VZ surface resulted in apical process detachment from the ventricular surface, dystrophic radial glia fibers, and substantial layering defects in the postnatal neocortex. Collectively, these data reveal novel roles for the laminin/integrin interaction in anchoring embryonic NSCs to the ventricular surface and maintaining the physical integrity of the neocortical niche, with even transient perturbations resulting in long-lasting cortical defects.
在胚胎发育过程中，发育中的大脑皮质的神经干细胞（NSC）位于脑室衬里的脑室区（VZ）。它们分别表现出与脑室表面和软脑膜基底膜接触的顶端和基底突起。这种独特的结构对于VZ的物理完整性和NSC子细胞的命运决定很重要。此外，较短的顶端突起对于核内有丝分裂迁移（INM）至关重要，它使VZ细胞在脑室表面进行有丝分裂。尽管它们很重要，但NSC与脑室黏附所需的机制仍知之甚少。我们之前已经表明，一类候选黏附分子层粘连蛋白存在于脑室区域，并且它们的整合素受体由NSC表达。然而，先前的研究仅证明了它们的相互作用在基底突起与上方软脑膜基底膜附着中的作用。在这里，我们使用抗体阻断和基因实验来揭示层粘连蛋白/整合素相互作用在顶端突起黏附和NSC调节中的额外新需求。使用阻断抗体在子宫内特异性靶向脑室区域短暂消除整合素结合和信号传导会导致异常的INM和NSC分裂方向的改变。我们发现这些缺陷在层粘连蛋白α2缺陷小鼠中也有观察到。使用多学科方法通过荧光转基因表达和多光子延时成像来分析干细胞行为的更详细分析表明，VZ表面层粘连蛋白/整合素信号的短暂胚胎破坏导致顶端突起从脑室表面脱离、营养不良的放射状胶质纤维以及出生后新皮质中的大量分层缺陷。总的来说，这些数据揭示了层粘连蛋白/整合素相互作用在将胚胎NSC锚定到脑室表面并维持新皮质生态位的物理完整性方面的新作用，即使是短暂的扰动也会导致持久的皮质缺陷。
