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Barbara Taylor
Director, Molecular and Cellular Biology Graduate Program
Director, Genetics Program
Professor, Zoology
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RESEARCH:
There is a growing realization that single genes have a significant influence in causing neurological disease and in affecting the performance of complex behaviors, such as human sexual preference. Interposed between the activity of single genes and behavior, in both vertebrates and invertebrates, are distinct groups of neurons that receive, integrate, and transmit information to effector organs. It is by examining the development of neurons and their incorporation into behaviorally-defined circuits that the link between genetic activity and behavioral outcome will be forged.
In vertebrates, the practical difficulties involved in dissecting the genetic basis of particular behaviors are formidable. However, small, fast-growing organisms like Drosophila with well-defined genetics serve as good models for understanding the relationship between genes and behaviors. My laboratory is using sexual differentiation in the fruitfly, Drosophila melanogaster to define the role that genes play in directing sexual behavior and brain development.
In Drosophila, sexual identity is directed in somatic cells through the activity of several genes, organized as a regulatory cascade. In most tissues, the genetic cascade has a single exit pathway through the gene, doublesex. Surprisingly, the story turned out to be different in the central nervous system (CNS). Analysis of sexual differences pointed to the existence of at least two output pathways: one pathway through the genedoublesex and the other pathway through the gene fruitless. Understanding the genetic regulation of sexual differentiation now requires clarifying the division of labor between the doublesex and proposed fruitless branches.
Two hypotheses outline the range of interactions between the two pathways: dual activity in sexually dimorphic neurons, which could be simultaneous or sequential, or exclusive activity in distinct subsets of neurons. From experiments in my lab, it is already clear that there will be neuronal representatives for each type of regulatory interaction proposed above. Behavioral analysis of doublesex or fruitless mutants have shown that male reproductive behaviors are the province of the fruitless gene. Through a variety of anatomical techniques, neurons have been discovered that are dependent on the doublesex pathway in both males and females whereas others appear to be regulated solely by the fruitless pathway. For a small subset of these identified neurons, the two functions appear to overlap.
By our analyses of molecular and cellular functions of the doublesex and fruitless genes in sex specific neurons, we will be able to link gene function to the generation of sexual behavior.