Michelle N. Arbeitman - US grants

In Drosophila melanogaster the fruitless (fru) gene is at the top of a branch of the sex determination hierarchy that functions in a small part of the central nervous system (CNS) to control all aspects of male courtship behavior. Fru, like other genes in the sex determination hierarchy, is sex-specifically regulated at the level of differential RNA splicing. The goal of the proposed research is to understand how male-specific FRU, which is a transcription factor, creates the potential for male-courtship behavior. The specific aim of the proposed research is the identification and characterization of male-specific FRU target genes from two developmental stages when male-specific FRU is expressed. The proposed research will proceed as follows. PolyA mRNA from heads of males, females and fru mutant males will be isolated and used as a template to make fluorescently labeled probes. A Drosophila EST cDNA microarray will be probed with two-color fluorescently labeled probes to identify genes that are more highly expressed in male brains as compared to female brains, and that required male-specific FRU for this higher expression. Alternative sources of probes are also presented in case a sufficient number of target genes are not identified. Potential male-specific FRU target genes will be analyzed to determine if they are genetically downstream of fru and to determine their genetic function in creating the potential for male courtship behavior.

DESCRIPTION (provided by applicant): Complex behaviors require that an animal can sense the external environment, integrate information and respond with the appropriate motor output. Therefore, understanding how complex behaviors are specified requires an integrated understanding of the development of the neural circuits that underlie these behaviors, as well as how physiological changes direct the adult behavioral output. Drosophila melanogaster has been a premiere model system for the study of the genetic basis of neural development and more recently for the genetic basis of complex behavior. Sophisticated molecular-genetic tools, coupled with cell imaging approaches are available for the study of Drosophila behavior and neural development. Furthermore, there is knowledge of the genetic determinants of some complex behaviors, including those that specify the neural substrates necessary for reproductive behaviors. Drosophila male courtship behaviors are genetically specified behaviors that are downstream of the sex determination hierarchy, a pre-mRNA splicing cascade that culminates in the production of sex-specific transcription factors encoded by fruitless and doublesex. Molecular-genetic studies have shown that fruitless is both necessary and sufficient for nearly all aspects of male courtship behaviors. The neurons in which the male-specific products of fruitless are expressed have been identified and shown to underlie the capacity for male courtship behaviors. This confluence of knowledge of male-specific transcription factors that specify behaviors, the identification of the neural circuit important for the behavior and the sophisticated molecular-genetic tools available for Drosophila genomic and cell imaging studies provides an unprecedented opportunity to gain insight into complex behaviors. The aims of this grant proposal are to study how sexual dimorphism in the nervous system is specified during development and how experience-dependent changes are encoded into the nervous system at adult stages. These studies will provide a foundation for understanding the genetic basis of behaviors in other animals, including humans.

[unreadable] DESCRIPTION (provided by applicant): A fundamental problem in neurobiology is understanding how the potential for complex behaviors are established. Drosophila melanogaster is an excellent model system to explore this question, given that a robust behavior, mating behavior, is genetically programmed. Drosophila male courtship consists of a series of steps directed towards a female. Females that have not been mated are receptive to male courtship behaviors, whereas those that have been recently mated will reject these advances. There is molecular-genetic evidence demonstrating that the doublesex (dsx) transcription factor plays a role in establishing courtship and mating behaviors in both males and females. However, in both males and females the specific function of dsx in the CNS has not been ascertained. This gap in our knowledge is limiting our ability to fully understand reproductive behaviors at a molecular-genetic level. The long-term goal of the research in my lab is understanding the genetic specification of sex-specific behaviors, using Drosophila as a model system. This will provide a foundation for understanding the specification of complex behaviors in other organisms, including humans, for which we have very limited understanding. The overall objective of the research proposed here is to determine if dsx plays an essential role in the CNS for mating behaviors. Our specific hypothesis is that dsx is required in the CNS in subsets of cells to specify some aspects of male courtship behavior, and to specify all or nearly all aspects of female mating behaviors. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Receptor Extracellular Domain Proteins have important functions in the nervous system, including mediating cell adhesion, cell signaling, neurite outgrowth and neuronal arborization patterns. Many human diseases are caused by defects in neuronal patterning that arise during development and/or physiological defects in extracellular receptor functions. The research in this proposal will make use of recently developed collection of plasmids that allow one to rapidly produce and systematically interrogate extracellular receptor domain interactions in a spatiotemporal manner, in an intact developing nervous system. Our previous genomic studies have identified receptor extracellular domain proteins as mediating differences in nervous system development that underlie the potential for complex behaviors. We will examine the role of these proteins in establishing sex-specific differences in nervous system functions that underlie reproductive behaviors.

Project Summary/Abstract A major goal of neuroscience research is to understand the molecular-genetic specification of behaviors and how the environment influences these mechanisms. Lack of knowledge of these molecular-genetic mechanisms is a major barrier to progress, as this limits knowledge about the interplay between nuclear, synaptic and physiological neuronal functions that direct behaviors and plasticity. Understanding the molecular- genetic mechanisms that drive complex behaviors in model systems is an important step. We propose a collaborative and unique approach to address our lack of understanding of complex behaviors. This study will be one of the first to examine on a genome-wide scale several molecular phenotypes that drive complex behaviors. We propose to use state-of-the-art tools, which are newly developed by our laboratory, to examine at a cell-specific level several molecular phenotypes. We will examine chromatin, transcription factor binding, gene expression and alternative pre-mRNA splicing in neural circuits that are well defined and known to underlie behavior. This innovative approach will allow us to identify the molecular process that are required to drive the potential and maintenance of this behavior, by examining these phenotypes during development and adult stages. In addition, we examine how the environment can modify behavior by examining the molecular and neural circuit basis of long-term memory formation. The project will be the first to elucidate and integrate, in a cell-specific manner, several molecular phenotypes that direct complex behavior, including how sex- differences in the molecular environment influence behavior. We will statistically integrate knowledge of all of these phenotypes to gain insights into the complex interplay between environment, molecular, neural circuit and behavioral phenotypes.