In the fly Drosophila melanogaster, new genetic, physiological, molecular and behavioral techniques for the functional analysis of the brain are rapidly accumulating. These diverse investigations on the function of the insect brain use gene expression patterns that can be visualized and provide the means for manipulating groups of neurons as a common ground. To take advantage of these patterns one needs to know their typical anatomy.

Current models describe male-specific fruitless (fruM) as a genetic ’switch’ regulating sexual behavior in Drosophila melanogaster, and they postulate that female (F) and male (M) doublesex (dsx) products control body sexual morphology. In contradiction to this simple model, we show that dsx, as well as fruM and non-sex-specific retained (retn), affect both male and female sexual behaviors. In females, both retn and dsxF contribute to female receptivity, and both genes act to repress male-like courtship activity in the presence or absence of fruM. In males, consistent with the opposing functions of dsxM and dsxF, dsxM acts as a positive factor for male courtship. retn also acts counter to fruM in the development of the male-specific muscle of Lawrence. Molecularly, retn seems to regulate sexual behavior via a previously described complex that represses zerknullt. Thus, we show that fru and dsx together act as a ’switch’ system regulating behavior in the context of other developmental genes, such as retn.

MicroRNAs (miRNAs) are small noncoding RNAs that regulate the expression of target transcript mRNAs. Many miRNAs have been defined, however their roles and the processes influenced by miRNA pathways are still being elucidated. A role for miRNAs in development and cancer has been described. We recently isolated the miRNA bantam (ban) in a genetic screen for modulators of pathogenicity of a human neurodegenerative disease model in Drosophila. These studies showed that upregulation of ban mitigates degeneration induced by the pathogenic polyglutamine (polyQ) protein Ataxin-3, which is mutated in the human polyglutamine disease spinocerebellar ataxia type 3 (SCA3). To address the broader role for miRNAs in neuroprotection, we also showed that loss of all miRNAs, by dicer mutation, dramatically enhances pathogenic polyQ protein toxicity in flies and in human HeLa cells. These studies suggest that miRNAs may be important for neuronal survival in the context of human neurodegenerative disease. These studies provide the foundation to define the miRNAs involved in neurodegenerative disease, and the biological pathways affected.

The Lombard effect-an increase in vocalization amplitude in response to an increase in background noise-is observed in a wide variety of animals. We investigated this basic form of vocal control in the cotton-top tamarin (Saguinus oedipus) by measuring the amplitude of a contact call, the combination long call (CLC), while simultaneously varying the background noise level. All subjects showed a significant increase in call amplitude and syllable duration in response to an increase in background noise amplitude. Together with prior results, this study shows that tamarins have greater vocal control in the context of auditory feedback perturbation than previously suspected.