The pattern of glomerular map formation defines responsiveness to aversive odorants in mice

In many species, the detection and recognition of odors is critical to regulate behaviors that are essential for survival, such as foraging for food and avoidance of predators. The formation of complex stereotypic connections between olfactory sensory neurons (OSNs) and second-order neurons in the olfactory bulb (OB) is believed to be important for accurate odorant information processing. In mice, ablation of OSNs that innervate the dorsal region of the OB leads to a loss of avoidance behavior in response to aversive and predator odorants (Kobayakawa et al., 2007). It remains to be determined whether the accurate formation of a glomerular map in this region of the OB is required for these innate responses. Here, we have generated mice that lack expression of the axon guidance receptor Robo-2 in OSNs and found that ablation of Robo-2 expression leads to mistargeting of subsets of OSN axons within the dorsal region of the OB. Furthermore, these mice show decreased avoidance behavior toward the predator odorant trimethyl-thiazoline. Our results indicate that the pattern of glomerular innervation in the OB is critical for innate behavioral responses in mice.