Key protein essential for smell and survival identified

Summary: The Orco protein is crucial for the survival of olfactory neurons in ants. Mutation of the orco gene in Harpegnathos saltator ants significantly reduced their number of olfactory neurons, thereby altering their social interactions.

This study highlights the importance of Orco in neuronal development and social communication in ants. Understanding these mechanisms can provide insights into sensory-mediated social behavior in animals and humans.

Highlights:

• The Orco protein is vital for the development and survival of olfactory neurons in ants.
• Mutant ants lacking Orco experienced significant neuronal death and impaired social interactions.
• The study offers new insights into how sensory systems and social behaviors are linked in animals.

Source: NYU

Although smell plays a considerable role in human social interactions (e.g., signaling fear or generating proximity), for ants it is vitally important.

Researchers at New York University and the University of Florida have discovered that a key protein called Orco, essential for olfactory cell function, is also essential for ant cell survival.

Their study showed that the mutation of orco gene in Harpegnathos Saltator jumping ants significantly reduced the number of olfactory neurons, suggesting that Orco is necessary for the development and life of these cells.

The results, published in Scientists progressoffer insight into the cellular and molecular basis of how animals socialize.

“Understanding how the nervous system develops is among the most pressing challenges in modern neuroscience,” said Bogdan Sieriebriennikov, a postdoctoral researcher in NYU's Department of Biology and first author of the study.

Detect smell and mutant ants

Ants have evolved around 400 olfactory receptors – a number more similar to humans than most other insects – through their use of pheromone communication.

“Ants, like humans, are highly social and display cooperative social behavior, and thus are an ideal system for studying sensory-mediated social behavior,” explained Hua Yan, assistant professor of biology at the University of Florida and lead author of the study.

“Extended odorant receptor genes allow ants to “talk” to each other in a large society of hundreds, thousands, or even up to a million individuals. »

Even for humans, who rely on other senses to communicate, smell is essential.

“Loss of function of odor receptor neurons leads to deficits in olfactory detection and is often associated with social isolation, neurological disorders such as schizophrenia, and social disorders such as autism,” Yan added.

To better understand how ants' sense of smell influences their social interactions, NYU researchers previously created the first genetically engineered ants using CRISPR to modify the ants' sense of smell. orco embarrassed. These “mutant” ants, lacking the Orco protein, underwent modifications to their olfactory organs and had difficulty interacting.

“We discovered that the antennae, which make up the ant’s “nose,” had very few cells. They were almost empty, suggesting that cells that detect smell were absent in the mutant ants,” Yan said.

Neuron survival depends on Orco

In their new study in Scientists progress, researchers used gene expression profiling of a single ant antenna nucleus and fluorescence microscopy to analyze olfactory cell development. It appeared that mutant insects lacking Orco lose most of their olfactory neurons before adulthood.

“The cells appear to be made normally and they start to develop: they grow, change shape and activate certain genes that they will need later, such as odor receptors,” Sieriebriennikov noted.

“Once developing cells activate odorant receptors, they very quickly begin to die in massive amounts.”

This neuronal death can be due to stress. Because the mutant ants' odor receptors cannot form a complex with Orco to travel to the cell membrane, the newly created receptors clog the organelles, leading to stress and death.

Such neuronal death may also show patterns particular to social insects. “So far, these unique processes have not been found in solitary insects and could provide important evidence for the evolution of neuronal development to accommodate the expansion of odorant receptor genes,” said Kayli Sieber, a doctoral student at the University of Florida and co-investigator. -first author of the study.

Interestingly, some odor receptors survived even without Orco. The cells in which they were present also expressed other types of receptors, suggesting that the activity they facilitate is essential for neuronal development.

“Some neurons must periodically “fire” in order to develop properly. Without Orco, the olfactory cells did not “fire” and complete their development, leading to their death,” Sieriebriennikov said.

Researchers also found that some odor receptors are present in non-odor cells, such as mechanosensory neurons that detect movement and glial cells, which surround neurons and help them function.

This may be due to imperfect gene regulation, which causes odorant receptors to be accidentally activated by neighboring genomic regions that normally regulate other genes in other cells. Alternatively, the receptors may have a new function in these cells, such as the odorant receptors found in glia of C. elegans worms or human sperm.

“Turning on odorant receptor genes in cells that don't detect odors could be completely useless for the organism – but then again, evolution tends to use such errors to give existing genes a new function, so can -maybe there is an exciting new role of odorant receptors in non-odorant cells that we will discover in the future,” Sieriebriennikov noted.

“Our results improve our understanding of the sensory systems of social insects, including olfactory neural development that establishes a framework for social communication,” Yan said.

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

About this research news in neuroscience and genetics

Author: Rachel Harrison
Source: NYU
Contact: Rachel Harrison – NYU
Picture: Image is credited to Neuroscience News

Original research: Free access.
“Orco-dependent survival of odorant receptor neurons in ants” by Bogdan Sieriebriennikov et al. Scientists progress

Abstract

Orco-dependent survival of odor receptor neurons in ants

Olfaction is essential to the complex social behavior of insects. To discriminate complex social signals, ants have evolved an increased number of odor receptor (Or) genes.

Mutations in the obligate odorant co-receptor gene orco cause the loss of approximately 80% of the glomeruli of the antennal lobe in the jumping ant Harpegnathos Saltator. However, the cellular mechanism remains unclear.

Here, we demonstrate massive apoptosis of odorant receptor neurons (ORNs) at mid to late stages of pupal development, likely due to ER stress in the absence of Orco.

Further analysis of the global and mononuclear transcriptome shows that although most orco-expressing ORNs die orco mutants, a small proportion of them survive: they express ionotropic receptor (IR) genes that form IR complexes.

Furthermore, we found that some Or genes are expressed in mechanosensory neurons and non-neuronal cells, likely due to regulatory leakage from nearby non-neuronal cells.Or Genoa.

Our results provide a comprehensive overview of ORN development and Or expression in H. saltator.