Unraveling the cell diversity in the accessory olfactory bulb (AOB) combining single cell transcriptomic analysis and electrophysiological approaches.

• Applicant: Andres Alberto Hernandez-Clavijo, Ph.D.
• Subject Area: Experimental and Theoretical Network Neuroscience
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552800903

Chemosensation, the organism's ability to detect chemical molecules in its environment, plays a crucial role in regulating behavior and physiology. In mammals, two primary chemosensory systems are distinguished: the main olfactory system, responsible for detecting general odorants, and the accessory olfactory system (AOS), which primarily senses pheromones governing direct behavioral responses. While the main system is well characterized, our understanding of the AOS and its structural and functional organization remains fragmentary. The AOS comprises three principal structures: i) the vomeronasal organ, ii) the accessory olfactory bulb (AOB), and iii) the amygdala/hypothalamus. Conceptually, these structures form a relatively straightforward detector-processor-effector system. However, despite its pivotal role in social and sexual signaling, the structural and functional organization of the AOB remains elusive. Notably, the relatively simple AOS organization presents a unique opportunity to investigate subcortical processing of external information that controls fundamental stereotyped behaviors. This proposal outlines an integrated, multifaceted approach to unravel the cellular composition of the mouse AOB. The methodological strategy combines single nuclei sequencing (snRNAseq), bioinformatic expression profiling, cell distribution mapping, electrophysiological characterization, and high-resolution 3D-reconstruction of AOB cells. Pilot studies demonstrate the feasibility of the proposed approach. To generate a comprehensive single-cell transcriptomic dataset for the mouse AOB, I propose a dissection procedure that allows qualitative and quantitative evaluation of AOB extraction. Subsequently, snRNAseq will extract the transcriptomic profiles, facilitating identification of AOB cell populations and specific marker genes through bioinformatic analysis. Cellular distribution in the AOB will be assessed via in situ hybridization and immunohistochemical analysis. Whole-cell patch-clamp recordings will elucidate the electrophysiological profile of individual AOB neurons, complementing transcriptomic classification. Post-hoc staining methods will enable morphological 3D-reconstruction of recorded cells. The combination of such diverse approaches will create a robust classification and characterization of mouse AOB cell diversity. Given the influence of pheromones on sex-specific behaviors, male- and female-specific AOB samples will be compared. Together, this multifaceted approach represents a critical first step in elucidating mouse AOB cell diversity and lays the groundwork for future research investigating pheromone signal processing and behavior regulation in mice.

• DFG Programme: Research Grants