NUCLEAR DYNAMICS IN RETINAL DEVELOPMENT AND HOMEOSTASIS

描述（由申请人提供）：神经元祖细胞和有丝分裂后神经元内的核运动是中枢神经系统发育的基本方面。因此，这些核运动的失败与严重的神经发育缺陷有关，如皮质层压异常、视神经发育不全和萎缩、视网膜发育不良、黄斑发育不全和小眼症。我们对这些核运动的生理相关性的理解有限，部分原因是目前缺乏适当的动物模型来干扰核分裂。我们最近验证了一种新的转基因策略，可以在体内干扰特定细胞和/或组织内的核运动。这种策略是基于“核骨架与细胞骨架的连接物”（LINC复合物）的诱导破坏，这是一种跨越核膜的大分子组装，为分子马达和细胞骨架网络提供锚点。使用这种转基因策略，我们将研究LINC复合物在相互动力学核迁移中的作用，包括视网膜祖细胞核与细胞周期相一致的振荡。由于核易位是皮层有丝分裂后神经元迁移的严格要求，我们将研究LINC复合体的破坏是否会影响新生视网膜神经元向其最终层状位置的迁移。在成人视网膜中，由于视网膜形成过程中诱导的核运动改变所导致的表型后果将被充分研究，这一组结果可能为先天性视网膜疾病提供新的模型。我们最近观察到，锥体核的定位在LINC复合体破坏时严重改变，这种表型与衰老的人类视网膜中锥体核的进行性错误定位惊人地相似。在这里，将在我们的小鼠模型中仔细分析锥体核错位的形态学和生理学后果。成人视网膜视锥核错位表型是由于视网膜发育过程中视锥前体核无法向顶端迁移所致。由于b型层蛋白直接与LINC复合物的核质界面相互作用，因此它们在锥体核定位中的作用将被研究。LINC复合物的细胞质界面由Nesprins代表，Nesprins是一组由四个不同基因编码的结构相关蛋白，其转录调控导致多种同种异构体的合成。目前，在中枢神经系统中表达的Nesprin异构体的身份仍然未知，这一知识缺口阻碍了对LINC复合物与分子马达相互作用的分子性质的研究。在这里，我们将鉴定在视网膜神经元及其祖细胞中表达的Nesprin亚型。由于nesprinin基因突变与越来越多的神经系统疾病有遗传联系，我们的研究结果可能进一步强调中枢神经系统特异性的Nesprins亚型，其突变是人类神经系统疾病的基础。

DESCRIPTION (provided by applicant): Nuclear movements within neuronal progenitors and post-mitotic neurons underlie fundamental aspects of CNS development. Accordingly, failure of these nuclear movements are associated to severe neurodevelopmental defects such as abnormal cortical lamination, optic nerve hypoplasia and atrophy, retinal dysplasia, macular hypoplasia and microphthalmia. Our limited understanding of the physiological relevance of these nuclear movements stems, in part, from the current lack of appropriate animal models to interfere with nucleokinesis. We recently validated a novel transgenic strategy that interferes with nuclear movements within specific cells and/or tissues in vivo. This strategy is based on the inducible disruption of "Linkers of the Nucleoskeleton to the Cytoskeleton" (LINC complexes), a family of macromolecular assemblies that span the nuclear envelope and provide anchor points for molecular motors and cytoskeletal networks to the nucleus. Using this transgenic strategy, we will examine the role of LINC complexes in interkinetic nuclear migration that consists of oscillations of retinal progenitor nuclei in phase with the cell cycle. Because nuclear translocation is strictly required for the migration of cortical post-mitotic neurons, we will examine whether LINC complex disruption affects the migration of newborn retinal neurons towards their final laminar position. The phenotypical consequences resulting from induced alterations of nuclear movements during retinogenesis will be fully examined in adult retinas, a set of results that may provide new models of congenital retinal disorders. We recently observed that cone nuclei positioning are severely altered upon LINC complex disruption, a phenotype that is strikingly similar to the progressive mispositioning of cone nuclei within the aging human retina. Here, the morphological and physiological consequences of cone nuclei mispositioning will be carefully analyzed in our mouse model. Cone nuclei mispositioning phenotype in adult retina originates from the inability of cone precursor nuclei to migrate apically during postnatal retinal development. Because B-type lamins directly interact with nucleoplasmic interfaces of LINC complexes, their involvement in cone nuclei positioning will be examined. Cytoplasmic interfaces of LINC complex are represented by Nesprins, a group of structurally- related proteins encoded by four distinct genes whose transcriptional regulation leads to the synthesis of multiple isoforms. Currently, the identity of Nesprin isoform(s) expressed in the CNS remains unknown, a knowledge gap that prevents the examination of the molecular nature of LINC complex interactions with molecular motors. Here, we will identify Nesprin isoforms expressed in retinal neurons and their progenitors. Because mutations of Nesprin genes are genetically linked to an increasing number of neurological disorders, our results may further emphasize CNS-specific isoforms of Nesprins whose mutations underlie human neurological disorders.