Barbara Taylor

Associate Professor

B.A., U Colorado 1974; Ph.D., U California, San Diego 1988

E-Mail: taylorb@science.oregonstate.edu, Phone: 541-737-5344, FAX: 541-737-0501, Address: Department of Zoology, Oregon State University, Corvallis, Oregon 97331-2914.

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 pursuing two complementary strategies to exploit sexual differentiation in the fruitfly, Drosophila melanogaster. Individual neurons can be inspected for variations in their properties or gene expression in known mutants that alter sexual development or behavior. Alternatively, neurons in males and females can be surveyed, initially without bias toward a particular behavior, by a variety of neuroanatomical and molecular techniques.

In Drosophila, sexual identity is transduced 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 CNS sexual differentiation pointed to the existence of at least two output pathways: one through doublesex and another through a distinct, new branch from the sex-determining cascade. On the basis of molecular and genetic evidence, a strong candidate for this new branch is the fruitless gene. 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.

These studies have yet to definitively link gene activity with identified neurons and neurons with particular behavioral circuits. To accomplish this goal, we are using cDNAs and antibodies to categorize neurons by their relevant genetic pathways. Further, functional mapping of particular behaviors to individual neurons or sets of neurons will be conducted through the use of genetically engineered "suicide" lines where distinct subsets of fruitless or doublesex neurons will be ablated to test the functioning of behavioral circuits missing certain components. From these experiments, the relationship between fruitless and doublesex gene activity in sex-specific neurons and behaviors will be determined. There is no assurance that the doublesex and fruitless pathways regulate all sexual differentiation in the CNS. These genes were discovered by disrupting easily visible sex-specific structures and courtship behaviors. We are examining mutations that affect subsets of reproductive behaviors, such as egg-laying by females, to identify additional genes that are necessary for the development of sex-specific neurons and muscles.

The second focus of my lab is to extend the identification of sex-specific neurons found in adult flies by neuroanatomical labeling techniques which impose no functional requirements for their discovery. Initially, we have concentrated on a survey of abdominal motorneurons due to the presence of a number of sexually dimorphic target tissues, such as genital muscles and gonads. Once new sex-specific neurons are known, then the regulatory hierarchies that control them can be determined.

By this two-pronged approach, the genetic activity of individual sex-determining genes will be related to the development and functioning of specific neurons in known behavioral circuits.

See also, further description of my work and a more extended list of references in: Molecular and Cell Biology Program