Identification and Characterization of Sex-Specific Transcripts in the Blood-Brain Barrier of Drosophila melanogaster

In Drosophila, a male displays a series of complex stereotypic acts in courting a female. This behavior is mainly controlled by male specific transcription factors that define male neuronal circuits inside the brain. In our lab, we have shown that male factors which are secreted outside of the CNS are also required for normal mating behavior. How these endocrine factors interact with the CNS is unknown. We have evidence that the Blood-Brain Barrier (bbb) plays an important role in this communication. Specific feminization of the bbb in otherwise normal males severely reduces their courtship. This suggests that male specific factors in the bbb play an important role in mating behavior. To identify these factors, I have used several genomic screens on dissected brains and isolated bbb cells. Studies that include mRNA sequencing and microarray hybridizations have identified several male-specific candidate genes with possible novel roles in courtship. I examined and found an adult role for one of the male preferentially expressed bbb-specific candidate genes, Hr46 in the regulation of male courtship behavior in the bbb. In addition, I have identified bbb-expressed microRNAs and their possible targets. I explored a role for miR-184, the most abundant miRNA in the bbb of Drosophila in male courtship. Alterations of the miR-184 levels in the adult bbb resulted in significant reduction in courtship suggesting its importance for normal male courtship in the bbb. Conditional RNAi knockdown of sinu, a miR-184 target in the adult bbb showed significant reduction in courtship indicating a physiological requirement in the bbb. Dye injection analysis shows that the the bbb permeability of miR-184 and sinu mutants is intact. quiver, another putative miR-184 target and a gene down-regulated in the mRNA sequencing experiment, was also found to affect male courtship behavior. Taken together, these data are the first to identify sex-specific transcripts in the bbb and bbb-specific miRNAs; and to reveal a novel role for miR-184 in the bbb for male courtship behavior of Drosophila melanogaster.