@article {796, title = {Endodomain diversity in the Drosophila Dscam and its roles in neuronal morphogenesis.}, journal = {The Journal of Neuroscience: The Official Journal of the Society for Neuroscience}, volume = {29}, year = {2009}, month = {2009 Feb 11}, pages = {1904-14}, abstract = {

Drosophila Down syndrome cell adhesion molecule (Dscam) can be variably spliced to encode 152,064 distinct single-pass transmembrane proteins. In addition to 19,008 possible ectodomains and two alternative transmembrane segments, it may carry endodomains containing or lacking exons 19 and 23. Here, we determine the role of Dscam endodomain diversity in neural development. Dscam with full-length endodomain is largely restricted to embryogenesis. In contrast, most Dscams lack exons 19 and 23 at postembryonic stages. As implicated from the expression patterns, removal of Dscam exon 19-containing variants disrupts wiring of embryonic neurons while silencing of Dscam transcripts lacking exon 19 or exon 23 effectively blocks postembryonic neuronal morphogenesis. Furthermore, compared with exon 19-containing Dscam, transgenic Dscam without exon 19 is more efficiently targeted to neurites and more potently suppresses axon bifurcation in Dscam mutant neurons. In sum, Dscam with or without exon 19 in its endodomain is used to govern different stage-specific neuronal morphogenetic processes, possibly due to differences in protein targeting.

}, keywords = {Amino Acid Motifs, Amino Acid Sequence, Animals, Cell Adhesion Molecules, Drosophila, Drosophila Proteins, Gene Targeting, Genetically Modified, Molecular Sequence Data, Morphogenesis, Neurogenesis, Neurons, Protein Structure, Tertiary}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.5743-08.2009}, author = {Yu, Hung-Hsiang and Yang, Jacob S and Wang, Jian and Huang, Yaling and Lee, Tzumin} } @article {790, title = {Transmembrane/juxtamembrane domain-dependent Dscam distribution and function during mushroom body neuronal morphogenesis.}, journal = {Neuron}, volume = {43}, year = {2004}, month = {2004 Sep 2}, pages = {663-72}, abstract = {

Besides 19,008 possible ectodomains, Drosophila Dscam contains two alternative transmembrane/juxtamembrane segments, respectively, derived from exon 17.1 and exon 17.2. We wondered whether specific Dscam isoforms mediate formation and segregation of axonal branches in the Drosophila mushroom bodies (MBs). Removal of various subsets of the 12 exon 4s does not affect MB neuronal morphogenesis, while expression of a Dscam transgene only partially rescues Dscam mutant phenotypes. Interestingly, differential rescuing effects are observed between two Dscam transgenes that each possesses one of the two possible exon 17s. Axon bifurcation/segregation abnormalities are better rescued by the exon 17.2-containing transgene, but coexpression of both transgenes is required for rescuing mutant viability. Meanwhile, exon 17.1 targets ectopically expressed Dscam-GFP to dendrites while Dscam[exon 17.2]-GFP is enriched in axons; only Dscam[exon 17.2] affects MB axons. These results suggest that exon 17.1 is minimally involved in axonal morphogenesis and that morphogenesis of MB axons probably involves multiple distinct exon 17.2-containing Dscam isoforms.

}, keywords = {Alternative Splicing, Animals, Brain, Cell Adhesion Molecules, Cell Differentiation, Cell Membrane, Dendrites, Developmental, Drosophila melanogaster, Drosophila Proteins, Embryo, Exons, Gene Expression Regulation, Genetically Modified, Growth Cones, Larva, Morphogenesis, Mushroom Bodies, Mutation, Neurons, Nonmammalian, Protein Isoforms, Protein Structure, Proteins, Tertiary, Transgenes}, issn = {0896-6273}, doi = {10.1016/j.neuron.2004.06.033}, author = {Wang, Jian and Ma, Xiaojun and Yang, Jacob S and Zheng, Xiaoyan and Zugates, Christopher T and Lee, Ching-Hsien J and Lee, Tzumin} } @article {788, title = {TGF-beta signaling activates steroid hormone receptor expression during neuronal remodeling in the Drosophila brain.}, journal = {Cell}, volume = {112}, year = {2003}, month = {2003 Feb 7}, pages = {303-15}, abstract = {

Metamorphosis of the Drosophila brain involves pruning of many larval-specific dendrites and axons followed by outgrowth of adult-specific processes. From a genetic mosaic screen, we recovered two independent mutations that block neuronal remodeling in the mushroom bodies (MBs). These phenotypically indistinguishable mutations affect Baboon function, a Drosophila TGF-beta/activin type I receptor, and dSmad2, its downstream transcriptional effector. We also show that Punt and Wit, two type II receptors, act redundantly in this process. In addition, knocking out dActivin around the mid-third instar stage interferes with remodeling. Binding of the insect steroid hormone ecdysone to distinct ecdysone receptor isoforms induces different metamorphic responses in various larval tissues. Interestingly, expression of the ecdysone receptor B1 isoform (EcR-B1) is reduced in activin pathway mutants, and restoring EcR-B1 expression significantly rescues remodeling defects. We conclude that the Drosophila Activin signaling pathway mediates neuronal remodeling in part by regulating EcR-B1 expression.

}, keywords = {Activin Receptors, Animals, Brain, Cell Differentiation, Cell Surface, DNA-Binding Proteins, Drosophila, Drosophila Proteins, Female, Genes, Larva, Lethal, Male, Missense, Mushroom Bodies, Mutation, Neural Pathways, Neuronal Plasticity, Neurons, Protein Isoforms, Proteins, Receptors, Signal Transduction, Smad2 Protein, Steroid, Trans-Activators, Transforming Growth Factor beta, Type I, Type II}, issn = {0092-8674}, author = {Zheng, Xiaoyan and Wang, Jian and Haerry, Theodor E and Wu, Ann Y-H and Martin, Josephine and O{\textquoteright}Connor, Michael B and Lee, Ching-Hsien J and Lee, Tzumin} } @article {787, title = {Drosophila Dscam is required for divergent segregation of sister branches and suppresses ectopic bifurcation of axons.}, journal = {Neuron}, volume = {33}, year = {2002}, month = {2002 Feb 14}, pages = {559-71}, abstract = {

Axon bifurcation results in the formation of sister branches, and divergent segregation of the sister branches is essential for efficient innervation of multiple targets. From a genetic mosaic screen, we find that a lethal mutation in the Drosophila Down syndrome cell adhesion molecule (Dscam) specifically perturbs segregation of axonal branches in the mushroom bodies. Single axon analysis further reveals that Dscam mutant axons generate additional branches, which randomly segregate among the available targets. Moreover, when only one target remains, branching is suppressed in wild-type axons while Dscam mutant axons still form multiple branches at the original bifurcation point. Taken together, we conclude that Dscam controls axon branching and guidance such that a neuron can innervate multiple targets with minimal branching.

}, keywords = {Animals, Cell Adhesion Molecules, Cell Communication, Cell Differentiation, Central Nervous System, Choristoma, Clone Cells, Developmental, Drosophila melanogaster, Drosophila Proteins, Embryonic Induction, Female, Ganglia, Gene Expression Regulation, Genes, Growth Cones, Invertebrate, Male, Mutation, Phenotype, Proteins, Reporter}, issn = {0896-6273}, author = {Wang, Jian and Zugates, Christopher T and Liang, Inray H and Lee, Ching-Hsien J and Lee, Tzumin} }