A small number of cholinergic neurons mediate hyperaggression in female Drosophila

Abstract

In the Drosophila model of aggression, males and females fight in same-sex pairings, but a wide disparity exists in the levels of aggression displayed by the 2 sexes. A screen of Drosophila Flylight Gal4 lines by driving expression of the gene coding for the temperature sensitive dTRPA1 channel, yielded a single line (GMR26E01-Gal4) displaying greatly enhanced aggression when thermoactivated. Targeted neurons were widely distributed throughout male and female nervous systems, but the enhanced aggression was seen only in females. No effects were seen on female mating behavior, general arousal, or male aggression. We quantified the enhancement by measuring fight patterns characteristic of female and male aggression and confirmed that the effect was female-specific. To reduce the numbers of neurons involved, we used an intersectional approach with our library of enhancer trap flp-recombinase lines. Several crosses reduced the populations of labeled neurons, but only 1 cross yielded a large reduction while maintaining the phenotype. Of particular interest was a small group (2 to 4 pairs) of neurons in the approximate position of the pC1 cluster important in governing male and female social behavior. Female brains have approximately 20 doublesex (dsx)-expressing neurons within pC1 clusters. Using dsxFLP instead of 357FLP for the intersectional studies, we found that the same 2 to 4 pairs of neurons likely were identified with both. These neurons were cholinergic and showed no immunostaining for other transmitter compounds. Blocking the activation of these neurons blocked the enhancement of aggression.

Cell types and neuronal circuitry underlying female aggression in Drosophila

“…No expression was observed in males in the majority of the lines used ( Figure 4 The cells labeled in males in two of the lines were not morphologically similar to pC1d or pC1e and these lines were not used for behavioral analysis in males. RNAseq analysis of pC1d and pC1e neurons confirmed that the cells expressed dsx and a gene associated with use of acetylcholine (ChAT) ( Figure 1-figure supplement 5), as previously described (Palavicino-Maggio et al, 2019;Rezával et al, 2016;Rideout et al, 2010;Zhou et al, 2014). Our data suggest that these cells might also express fru (Figure 1-figure supplement 5).…”

“…Optogenetic activation dramatically increased aggression in lines labelling aIPg neurons, while inactivation diminished these actions. Analysis using EM-level connectomics revealed strong connectivity between these aIPg neurons and two members of the pC1 cluster, a group of related cell types previously linked to social behaviors (Hoopfer et al, 2015;Palavicino-Maggio et al, 2019;Wang et al, 2020;Zhou et al, 2014). In particular, pC1d is the top pre-synaptic input to aIPg neurons, devoting ~13% of its output synapses to them.…”

The Neural Basis for a Persistent Internal State inDrosophilaFemales

“…Thermogenetic activation of pC1 neurons in females drives chasing (Rezával et al, 2016;Wu et al, 2019), a male-specific behavior, and also aggressive behaviors toward females (Palavicino-Maggio et al, 2019). Taken together these data suggest that female pC1 neurons can drive multiple distinct behaviors, similar to male P1 neurons, but whether female pC1 neurons can drive persistent changes in behavior and persistent neural activity, has not yet been investigated.…”

“…In sum, we found that for minutes following pC1-Int activation, females produced a variety of behaviors directed at the male. Some of these appear aggressive, such as shoving and headbutting (Nilsen et al, 2004;Palavicino-Maggio et al, 2019), while others resemble male courtship behaviors, such as chasing and unilateral wing extension. These behaviors typically peaked in the d3 condition, where they remained high 30 minutes after male introduction.…”

“…2F). Activation of a subset of pC1 neurons is also known to drive aggressive behaviors towards females during stimulation (Palavicino-Maggio et al, 2019), but whether the quality of aggression generated towards males versus females (and any persistence) is similar remains to be determined. As one of our manually scored behaviors, 'female approaching' (Fig.…”