Regulation of Neurotransmission and Behavior

描述(由申请人提供)： 化学突触的神经递质分泌的发展、维持和控制是神经系统正常运作所必需的神经通讯的基础。由于发育过程中发现的遗传或表观遗传异常，突触传递和连接的缺陷可能会导致大脑功能受损。特别是，经典神经递质和神经肽的调节胞吐作用是神经元之间有效交流所必需的突触前输入的关键因素。本实验室研究的总体目标是更好地了解控制神经胞吐的分子、细胞和发育机制。我们的假设是，负责膜运输和囊泡融合进行神经传递的分子机制的组成的发育调节，有助于发展神经元在最初接触和形成突触期间的沟通方式，并最终塑造成熟神经系统的突触生理学。为了解决这一假设，我们将重点放在SNAP-25蛋白上，它是SNARE复合体的关键元件，介导膜融合以释放递质。我们认为，从结构性表达的同源物SNAP-23到SNAP-25亚型的调控表达，在介导生长轴突到能够引起神经递质释放和突触活性的功能性突触的囊泡融合中起着关键作用。我们的研究利用了之前通过这笔资金在小鼠身上开发的Snap25基因突变，以及将在当前时期产生的条件突变。在具体目标1中，实验旨在利用Snap25缺失突变体检测培养细胞和胎儿大脑发育中自发神经递质释放的作用。在特定的目标2中，我们将使用延长SNAP-25a亚型过度表达的突变来检验SNAP-25亚型中的转换是否是出生后发育过程中突触传递成熟所必需的。最后，在特定的目标3中，我们将通过研究Cre重组酶的诱导表达控制的一个条件性Snap25基因突变的突触功能，将我们的分析扩展到出生后发生的突触发生和突触成熟的后期步骤，以及在长期的神经退化过程中。如果成功，这些研究将揭示SNAP-25及其异构体在发育过程中的作用，以及正常大脑功能所需的突触可塑性，以及突触前神经传递机制的异常如何参与神经精神疾病。

DESCRIPTION (provided by applicant): The development, maintenance and control of neurotransmitter secretion at chemical synapses underlie the neuronal communication necessary for the proper function of the nervous system. Deficits in synaptic transmission and connectivity, resulting from genetic or epigenetic abnormalities revealed during development, are likely to contribute to impaired brain function. In particular, regulated exocytosis of classical neurotransmitters and neuropeptides is a key factor that underlies the necessary presynaptic input for effective communication between neurons. The overall goal of the research of our laboratory is to gain a better understanding of the molecular, cellular and developmental mechanisms which control neuroexocytosis. Our hypothesis is that the developmental regulation of the composition of the molecular machinery responsible for membrane trafficking and vesicular fusion for neurotransmission is instrumental in developing how neurons communicate during the initial contact and formation of synapses, and ultimately in sculpting the synaptic physiology of the mature nervous system. To address this hypothesis, we have focused on the protein SNAP-25, a key element of the SNARE complex mediating membrane fusion for transmitter release. We propose that the transition from a constitutively expressed homologue, SNAP-23, to the regulated expression of SNAP-25 isoforms plays a key role in mediating vesicle fusion for growing axons to functional synapses capable of evoked neurotransmitter release and synaptic activity. Our investigations make use of Snap25 gene mutants in the mouse developed through previous funding of this grant and a conditional mutation to be generated during the present period. In Specific Aim 1, experiments are designed to examine the role of spontaneous neurotransmitter release in cultured cells and fetal brain development using Snap25 null mutants. In Specific Aim 2, we will examine whether the switch in SNAP-25 isoforms is required for maturation of synaptic transmission during postnatal development using a mutation that prolongs overexpression of the SNAP-25a isoform. Finally in Specific Aim 3, we will extend our analysis to study later steps of synaptogenesis and synaptic maturation that occur after birth, and in the long-term neurodegenerative processes, by investigating synaptic functions of a conditional Snap25 gene mutation controlled by inducible expression of Cre recombinase. If successful, these investigations will shed light on the roles of SNAP-25 and its isoforms during development and for synaptic plasticity required for normal brain function, and how abnormalities in presynaptic mechanisms of neurotransmission are involved in neuropsychiatric disease.