NYC Gazette

Researchers from New York University and the University of Florida have discovered that a protein named Orco, essential for olfactory cell function, is also critical for the survival of these cells in ants. Their study, published in Science Advances, reveals that mutating the orco gene in Harpegnathos saltator jumping ants significantly reduces the number of olfactory neurons, indicating that Orco is vital for the development and longevity of these cells.

"Understanding how the nervous system develops is among the most pressing challenges in modern neuroscience," said Bogdan Sieriebriennikov, a postdoctoral fellow at NYU’s Department of Biology and the study’s first author.

Ants possess approximately 400 smell receptors due to their reliance on pheromone communication. "Ants, like humans, are highly social and display cooperative social behavior, and thus provide an ideal system to study sensory-mediated social behavior," explained Hua Yan, assistant professor of biology at the University of Florida and the study’s senior author. Expanded odorant receptor genes enable ants to communicate within large societies.

NYU researchers previously used CRISPR technology to create genetically engineered ants by editing the orco gene. These mutant ants exhibited altered smell organs and had difficulty interacting. "We found that the antennae—which are the ‘nose’ of the ant—had very few cells. They were almost empty, suggesting that the cells that sense smell were absent from the mutant ants," said Yan.

In their new study, researchers employed single-nucleus gene expression profiling and fluorescence microscopy to analyze olfactory cell development. They found that mutant insects lacking Orco lose most of their olfactory neurons before reaching adulthood. "The cells appear to be made normally... Once the developing cells turn on the odorant receptors, very soon they start dying in massive amounts," noted Sieriebriennikov.

This neuronal death may result from stress caused by newly made receptors clogging organelles due to their inability to form a complex with Orco. This process has not been observed in solitary insects and may provide evidence of neural development evolution adapting to expanded odorant receptor genes.

Interestingly, some odorant receptors survived without Orco. Cells with these receptors also expressed other types of receptors necessary for neuronal development. "Some neurons must periodically ‘fire’ to develop properly... Without Orco, smell cells did not ‘fire’ and complete their development, leading to their death," added Sieriebriennikov.

The researchers also discovered some odorant receptors present in non-smell cells such as mechanosensory neurons and glia. This might be due to imperfect gene regulation or possibly indicate a new function for these receptors in non-smell cells.

"Our findings enhance our understanding of social insects’ sensory systems, including olfactory neural development that establishes a framework for social communication," said Yan.

Other authors include Olena Kolumba, Jakub Mlejnek, and Shadi Jafari. The research was supported by grants from the National Institutes of Health (R01-DC020203, T32-DC015994), National Science Foundation Industry-University Cooperative Research Center for Arthropod Management Technologies (#IIP1821914), and Human Frontier Science Program (LT000010/2020-L).