Figure 4.

Sensory responses to sulfated steroids can be grouped into functional categories. (a) We identified 8 clusters of similar responsiveness to sulfated steroids at 10 μM identified in the VSN data set. We show normalized Δr_monotonic responses of the 75 steroid-responsive VSNs in their respective clusters. Asterisks indicate clusters we did not encounter in the AOB data set. Cluster 1 included several neurons that responded to 1:100 female mouse urine, and others that did not. As these may represent functionally separable populations, we separated them into urine-unresponsive (cluster 1a) and urine-responsive (cluster 1b) subgroups. (b) Molecular features that, for clusters 1, 3, 6, 8, and 10, distinguished active from inactive steroids. Common features are highlighted in red. The grayed groups in cluster 3 indicated that a distinguishing feature of steroids that activate neurons in this cluster is the lack of a hydroxyl group at carbon 13. (c) We identified clusters of responsiveness to sulfated steroids at 10 μM in the AOB neuron data set independently of the VSN cluster identities. We show Δr_norm responses of AOB neurons in their respective clusters. The “unclustered” region shows the neurons most associated with marginally-responsive neurons. Asterisks indicate clusters we did not encounter in the VSN data set. (d) Discriminability index (d′) comparing the steroid response patterns found in the VSN data set to the AOB data set along the first 3 linear discriminant eigenvectors. The dotted line indicates d′ = 3, corresponding to a high degree of separability. Asterisks indicate clusters not present in the AOB data set.