Summary: New findings challenge our understanding of fruit fly social behaviors. While traditionally thought to rely primarily on chemical receptors for social interactions, the fruit fly’s visual system plays a pivotal role too.
By manipulating the visual feedback neurons in male fruit flies, researchers discovered that their social inhibitions were altered, leading males to court other males. This novel insight can potentially enlighten our comprehension of social behaviors in humans, including those with bipolar disorder and autism.
Fruit flies were believed to rely mainly on chemical signals for social interaction; new research suggests their visual system is also integral.
Altering the GABARAP/GABAA receptor signaling in visual feedback neurons in male fruit flies affected their social behaviors.
Similar genes found in the human brain control the fruit fly’s visual neurons, providing insights into human social behaviors and certain psychiatric conditions.
Source: Cornell University
Male fruit flies don’t usually like each other. Socially, they reject their fellow males and zero in on the females they discern via chemical receptors – or so scientists thought.
New research from Cornell University biologists suggests the fruit fly’s visual system, not just chemical receptors, are deeply involved with their social behaviors. The work sheds light on the possible origin of differences in human social behaviors, such as those seen in people with bipolar disorder and autism.
The paper, “Visual Feedback Neurons Fine-tune Drosophila Male Courtship via GABA-mediated Inhibition,” published in Current Biology on Sept. 5.
Many species of animals use vision to regulate their social behaviors, but the underlying mechanisms are largely unknown. In fruit flies, vision is thought to be used explicitly for motion detection and following, not to regulate social behaviors – but the researchers found that may not be the case.
“In our study, we found that hyperactivating the visual system overran the inhibition generated by chemical signals emitted by the male fly to say to the other male, ‘Okay, you know, I’m another male, don’t mess with me,’” said senior author Nilay Yapici, assistant professor of neurobiology and behavior.
“Surprisingly, increasing the visual gain in the brain somehow overrides the chemosensory inhibition, attracting male flies to other males.”
The researchers found that altering the GABARAP/GABAA receptor signaling in visual feedback neurons in the male brain affected the flies’ social inhibitions. When GABARAP is knocked down in the visual system, the males unexpectedly exhibit increased courtship toward other males.
The researchers have found that genes similar to those in the human brain control the fruit fly’s visual neurons. Decreasing GABA signaling in the human brain has been associated with social withdrawal characteristics in conditions such as autism and schizophrenia.
“Our results offer a promising avenue for investigating how these proteins regulate social behaviors in the mammalian brain and their potential contribution to human psychiatric conditions,” said lead author Yuta Mabuchi, Ph.D. ’23.
About this social and visual neuroscience research news
Visual feedback neurons fine-tune Drosophila male courtship via GABA-mediated inhibition
GABARAP is required in lamina tangential neurons to suppress male-male courtship
Dro-GABARAP function in Lat neurons can be rescued by its human ortholog
Hyperactivating Lat or LC10a neurons induces male-male courtship
Lat neurons fine-tune male tracking during courtship via the LC10a-Fru-P1 circuit
Many species of animals use vision to regulate their social behaviors. However, the molecular and circuit mechanisms underlying visually guided social interactions remain largely unknown.
Here, we show that the Drosophila ortholog of the human GABAA-receptor-associated protein (GABARAP) is required in a class of visual feedback neurons, lamina tangential (Lat) cells, to fine-tune male courtship. GABARAP is a ubiquitin-like protein that maintains cell-surface levels of GABAA receptors.
We demonstrate that knocking down GABARAP or GABAAreceptors in Lat neurons or hyperactivating them induces male courtship toward other males.
Inhibiting Lat neurons, on the other hand, delays copulation by impairing the ability of males to follow females. Remarkably, the fly GABARAP protein and its human ortholog share a strong sequence identity, and the fly GABARAP function in Lat neurons can be rescued by its human ortholog.
Using in vivo two-photon imaging and optogenetics, we reveal that Lat neurons are functionally connected to neural circuits that mediate visually guided courtship pursuits in males.
Our work identifies a novel physiological function for GABARAP in regulating visually guided courtship pursuits in Drosophila males. Reduced GABAA signaling has been linked to social deficits observed in the autism spectrum and bipolar disorders.
The functional similarity between the human and the fly GABARAP raises the possibility of a conserved role for this gene in regulating social behaviors across insects and mammals.