Can studies of behaviors such as aggression, sleep patterns, responses to light or gravity in the common fruit fly, Drosophila melanogaster, lead us to learning about neuronal networks in the human brain, and ultimately help us decode the mysteries of human behavior? These questions regarding behavioral phenotypes are currently being investigated at The Neurosciences Institute.

Studies at the Institute have shown that behavior is sensitive to subtle changes in the gene networks. Investigators have devised experiments to observe and document changes in the gene networks in mutant Drosophila that respond differently to light (phototaxis) and gravity (geotaxis), or have higher or lower metabolism and locomotor activity. Gene networks have also been analyzed to identify genes that affect the sleep/wake cycle, mating speed, courtship song, circadian rhythms, aggression, and temperature induced-paralysis.

Gene Networks – Implication for Evolutionary Biology
Current molecular models in genetics assume that elements of a gene network are specific in their interaction and that their relationships are stable. Scientists at the Institute have analyzed the interactions among a set of 16 mutations of Syntaxin-1 (Syx-1A) gene, which affects synaptic transmission between neurons and is involved in loss of coordination. The results of this research indicate that functional relationships between the 16 genes vary, which suggests a need for redefining the assumption of stability for interactions within gene networks.

This research allows probing into the concepts of degeneracy and robustness in gene networks, concepts of great concern to evolutionary biologists or paleontologists as well as scientists from many other disciplines. Degeneracy and robustness together refer to the fact that the physical appearance of organisms (phenotype) can remain the same despite the loss of, or mutation of genetic information (genotype). Research on the Syx-1A has great significance for showing the relationship between mutations and phenotype; this work may potentially lead us to understand what aspects of degeneracy are important.

To Rove or to Sit - That is the Question!
The fruit fly variants Rover and Sitter, have different metabolisms which lead them to use different scavenging or foraging strategies. Rover traverses large areas during feeding, while Sitter covers a small area. The two forms are naturally occurring fly mutations, providing the opportunity to study the molecular basis for behavioral polymorphism. Research at the Institute has revealed that interaction between gene and metabolic networks influence expression of mRNA and metabolite molecules between the two forms. It is found that Sitters are in a state of mitochondrial dysfunction. Low mitochondrial activity is known to cause weakness and fatigue, and has been linked to aging as well as age related diseases such as Parkinson’s disease and diabetes. The main difference between the Rover and Sitter forms is caused by only 12% difference in expression level of an enzyme (cGMP-dependent protein kinase) that is formed by the foraging gene.

Aggression - Fruit Flies in the Boxing Ring
In order to study aggressive behavior in Drosophila, the Institute scientists carefully observed fruit flies fight over territory and battle one another in confrontations, not unlike boxing matches that captivate audiences and increase ratings of cable television stations. After 21 generations of selection for aggressive behavior, the gene expression in Drosophila mutations demonstrated increased aggression. These differences in some cases reflected higher expression level of the genes known to be involved in recognizing odors. Read our latest press release.

Geotaxis – Effects of Gravity on Behavior
It is known that some fruit flies respond to gravity by choosing to fly into either high or low level tubes when given choices in glass mazes. The flies are respectively described as having negative (high) or positive (low) geotaxis. By selecting ‘high’ and ‘low’ forms over many generations and studying the gene networks of these two groups, it has been determined that expressions of a wide variety of genes influence geotaxis. Among others, these include members of gene networks involved in neuronal cell fate determination, neuronal signaling, circadian rhythms, and basic biological mechanisms. The complexity of geotaxis confirms the need for analysis beyond single-gene mutations.

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