| Non-Scientific Abstract Large-scale screening of the genomes of model organisms
enables us to identify novel genes without requiring prior knowledge of their functions or interactions.We are
interested in finding genes involved in retinal axon guidance in the fruit fly, Drosophila
melanogaster. The screen described in this paper uses an existing molecular system,Gal4, to force
high-level expression of candidate genes in Drosophila photoreceptor neurons. The larvae resulting from
this genetic manipulation are screened for axon patterning irregularities in the optic lobe. Genes
demonstrating axon guidance defects are then subjected to further analysis. Because many guidance mechanisms
are conserved at a molecular level, identification and characterization of these genes is likely to prove
useful in understanding how similar systems function in higher vertebrates.
Abstract
Traditional genetic screens employ methods such as chemical mutagenesis, radiation and transposon
mutagenesis in order to create random mutations. These tend to reduce or eliminate gene function.However,
genes important for axon guidance can also disrupt axon targeting when expressed at ectopic locations or at
high levels. Thus, a promising approach for identifying axon guidance regulators is to screen for genes that
disrupt axon targeting when over- or misexpressed. The precise regularity of the Drosophila visual
system provides an ideal context in which to screen for axon guidance phenotypes. In this screen,we use the
UAS Gal4 system to drive high level, photoreceptor neuron-specific expression in a collection of fly lines
containing transposable elements with multiple Gal4 binding sites inserted throughout the genome. The existing
collection of inserts has been mapped onto the Drosophila genome, making this a viable and efficient
strategy. Approximately 1900 lines were screened; 21 insertions were identified in 13 different genes that led
to axon guidance defects when driven in the eye. |
