Investigating the molecular mechanisms of early neuronal morphogenesis

总结 细胞形态是多细胞生物体中体细胞最显著的特征之一， 与细胞功能密切相关。神经元和其他极化细胞如何形成它们的形态， 虽然我们对此知之甚少，但培养中分离细胞的自发形态发生表明， 用于形态学的指令通常被固有地编码。我们之前发现了一种序列特异性RNA 结合蛋白，蓬乱，作为一个因素，这是必不可少的建立早期神经元形态 以及作为能够赋予非神经元来源的细胞类似形状的蛋白质。蓬头 识别主要在编码区mRNA内的独特结合基序， 抑制。目前还不清楚Unkempt是如何调节翻译的，以及翻译或其他功能是否 蓬头垢面的形态是其诱导细胞极化的关键。在这里，我们寻求解决这个问题， 破译蓬乱驱动的细胞形状重塑的机制基础。我们的初步研究 这表明在Unkempt蛋白质相互作用网络中， 低复杂性结构域（LCD）和CCR 4-NOT复合物是诱导细胞凋亡所必需的。 形态发生我们提出了三个具体的目标来研究CCR 4的分子和细胞作用， 不复杂，作为一个关键效应的蓬乱控制的细胞形态发生。首先，我们将调查 Unkempt-CCR 4-NOT相互作用的性质及其对目标消息命运的影响， 特别是它们poly（A）尾长度、稳定性和翻译。第二，我们将审问招募 以及CCR 4-NOT在Unkempt诱导的细胞形态发生中的作用。第三，我们将确定 Unkempt的翻译后修饰对它与CCR 4-NOT复合物和RNA的相互作用，以及 作为其对局部蛋白质翻译的控制。这项研究将揭示早期的分子基础， 神经元形态发生，并有助于我们对控制细胞的线索的一般理解， 形态学在发育和疾病中的作用。

SUMMARY Cellular morphology is one of the most distinctive features of somatic cells in multicellular organisms and is intimately linked with cellular function. How neurons and other polarized cells commit to their morphologies is poorly understood, but spontaneous morphogenesis of dissociated cells in culture suggest that the basic instructions for morphology are often intrinsically encoded. We previously identified a sequence-specific RNA- binding protein, Unkempt, as a factor that is essential for the establishment of the early neuronal morphology and as a protein that is capable of endowing a similar shape to cells of nonneuronal origin. Unkempt recognizes a unique binding motif predominantly within coding regions mRNAs the translation of which it suppresses. It is unclear how Unkempt regulates translation, and whether translation or another functional modality of Unkempt is critical to its induction of cell polarization. Here, we seek to solve this problem by deciphering the mechanistic basis of Unkempt-driven remodeling of cellular shape. Our preliminary studies indicate that in the broad protein-protein interaction network of Unkempt, the interaction between Unkempt’s low-complexity domain (LCD) and the CCR4-NOT complex is exquisitely required for the induction of cell morphogenesis. We propose three specific aims to investigate the molecular and cellular roles of the CCR4- NOT complex as a critical effector of Unkempt-controlled cell morphogenesis. First, we will investigate the nature of Unkempt – CCR4-NOT interactions and their impact on the fate of the targeted messages, focusing in particular on their poly(A) tail length, stability, and translation. Second, we will interrogate the recruitment and function of CCR4-NOT in Unkempt-induced cell morphogenesis. Third, we will determine the effect of post-translational modifications of Unkempt on its interactions with the CCR4-NOT complex and RNA, as well as its control of local protein translation. This study will shed light on the molecular underpinnings of the early neuronal morphogenesis and contribute to our general understanding of the cues that control cellular morphology in development and disease.