Connectivity and Development of the Drosophila Larval Visual System

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

The visual system of the fruitfly Drosophila has proven to be an excellent model to identify conserved genes that control how the visual system of an animal is formed. Much has been discovered about the photoreceptors and the structure of the Drosophila eye. In contrast, the central (brain) neurons that process visual information have received less attention. This grant will allow the Hartenstein lab to investigate the structure and development of the simple central visual neuropile (the circuit, made by axons, dendrites and synapses) of the Drosophila larval brain. Experiments in aim #1 (anatomical circuitry) will address the pattern of neuronal connections in the visual neuropile and map the neurons that send axons from the brain to the ventral nerve cord. Aim 2 (function) addresses how larval behavior is influenced by light stimuli. A functional assay (head turning away from a local light source) will be used to analyze quantitatively the effect of directed light on movement. Aim 3 (development) is based on previous findings indicating that many elements of the central visual system are derived from the same embryonic field that also gives rise to the eye. This eye field expresses a network of early eye genes (called eyeless, eyes absent, sine oculis, and dachshund) whose function is well established for the eye. Dr Hartenstein and his colleagues will investigate the expression and function of the early eye genes in the developing central visual system. Aim 4 (gene discovery) will use a novel "gene trap" method to screen for genes that are expressed only in the visual neuropile. The neurons expressing these genes will be characterized. A long-term goal of the research is the characterization of genes that are preferentially expressed in the visual neuropile. Broader Impact: Genetic screens and phenotypic analyses in Drosophila have revealed many aspects of developmental neurobiology. The findings resulting from this research are likely to provide insight into a highly conserved gene network, the early eye genes, that plays multiple roles in vertebrate development. At the same time, this research program serves as a vehicle for undergraduate teaching. The PI is responsible for a large undergraduate class, Developmental Biology, taken yearly by 150-200 UCLA undergraduates. Many undergraduates (between 6 and 10 per year) rotate through the lab and conduct short (1-3 quarters) research projects. These students are teamed up with postdocs or graduate students and gain practical research experience. The preliminary work leading to several of the proposed aims was conducted together with undergraduate students. Among the undergraduates is a sizeable number of minority students. UCLA has a special program (CARE) that awards short term fellowships for minority students to conduct research. The PI's lab currently hosts one CARE student, Luis Garcia, who visualized the photoreceptor terminals in the larval optic neuropile (aim #1).