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.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD040279-03
Application #
6638018
Study Section
Visual Sciences C Study Section (VISC)
Program Officer
Henken, Deborah B
Project Start
2001-04-01
Project End
2006-03-31
Budget Start
2003-04-01
Budget End
2004-03-31
Support Year
3
Fiscal Year
2003
Total Cost
$168,324
Indirect Cost
Name
University of California Los Angeles
Department
Biochemistry
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Hattori, Daisuke; Chen, Yi; Matthews, Benjamin J et al. (2009) Robust discrimination between self and non-self neurites requires thousands of Dscam1 isoforms. Nature 461:644-8