AXON GIUDANCE AND TARGETING IN DROSOPHILA

描述（由申请人提供）：Dscam是一种轴突导向受体， 在果蝇的神经系统中， 系统Dscam功能丧失表型已详细描述， 一种叫做Bolwig神经的胚胎神经。Dscam的表型研究 突变体表明，Dscam蛋白是介导短距离 BN和中间靶之间的相互作用。Dscam还需要用于 发育中的胚胎中其他连接的特化。Dscam蛋白 含有10个IG重复序列，6个纤连蛋白III型重复序列，单个跨膜 片段和具有多个Dock衔接子结合位点的胞质尾区 蛋白质，一种连接Dscam和肌动蛋白细胞骨架的信号成分 监管部门Dscam的选择性剪接可能导致超过38，000种形式的 受体。这些受体具有相同的结构域结构，但在 4个不同结构域的氨基酸序列。其中三个IG结构域和一个 跨膜结构域是可变的。这种变化反映了使用 替代外显子。 在这份提案中，将确定以BN表示的Dscam的具体形式 采用RT-PCR技术。转基因拯救实验将用于验证这一点， 形式在BN中起作用。含有不同可变结构域的转基因将 通过在BN中靶向表达来测试功能。另外的实验 将针对确定Dscam的表达模式， 同种型在发育中的胚胎和发育中的眼睛的视盘使用 原位杂交和RT-PCR技术。这些研究将构成 确定不同Dscam亚型是否有助于 轴突导向和定位的分子密码果蝇Dscam 与唐氏综合症相关的人类基因结构相关， 这项资助中描述的可能会提供对大脑异常的见解， 唐氏综合症患者的发展。

DESCRIPTION (provided by applicant): Dscam is an axon guidance receptor that is required for the formation of neuronal connections in the Drosophila nervous system. Dscam loss-of-function phenotypes have been characterized in detail for an embryonic nerve called Bolwig's nerve (BN). Phenotypic studies of Dscam mutants suggest that Dscam protein is critical for mediating a short-range interaction between BN and an intermediate target. Dscam also is required for the specification of other connections in the developing embryo. Dscam protein contains 10 Ig repeats, 6 fibronectin type III repeats, a single transmembrane segment and a cytoplasmic tail with multiple binding sites for the Dock adapter protein, a signaling component connecting Dscam to actin cytoskeletal regulators. Alternative splicing of Dscam may lead to more than 38,000 forms of the receptor. These receptors share the same domain structure, but differ in amino acid sequence in 4 different domains. Three of the Ig domains and the transmembrane domain are variable. This variability reflects the use of alternative exons. In this proposal, the specific form of Dscam expressed in BN will be determined using RT-PCR. Transgene rescue experiments will be used to verify that this form is functional in BN. Transgenes containing different variable domains will be tested for function by targeted expression in BN. Additional experiments will be directed towards determining the pattern of expression of Dscam isoforms in the developing embryo and the developing eye imaginal disc using both in situ hybridization and RT-PCR techniques. These studies will form the foundation for determining whether different Dscam isoforms contribute to a molecular code for axon guidance and targeting. As Drosophila Dscam is structurally related to a human gene implicated in Down Syndrome, the studies described in this grant may provide insights into the abnormalities in brain development in Down Syndrome patients.