Spatial organization and detection of social odors in mouse primary olfactory system.

The detection of olfactory cues is essential to signal food, predators, and social encounters. To determine how the sensory detection of physiologically relevant odors is systematically mapped into the mouse primary olfactory system, we used multiplexed error-robust fluorescent in situ hybridization (MERFISH) to construct a molecular atlas of olfactory receptor (OR) expression in the main olfactory epithelium (MOE) and olfactory bulb (OB). We comprehensively quantified the expression of the mouse OR repertoire and uncovered stereotypical gradients of sensory neuron distribution in the MOE along two axes, central-to-peripheral and apical-to-basal. Projections of sensory neurons mirror these two MOE gradients along the dorsal-ventral and anterior-posterior axes of the OB, respectively. Integration with sequencing data revealed candidate signaling molecules underlying this spatial organization. Co-imaging OR and activity marker expression identified distinct spatial domains of sensory responses in the MOE and OB, providing a topographical basis for olfactory responses to ethologically relevant odors.