Figure 5. Identification of new olfactory sensory neuron (OSN) classes.
(A) Co-labeling experiments with Ir41a-Gal4 show that both Ir25a-T2A-QF2 and Ir8a-T2A-QF2 label the VC5 glomerulus (orange), and also a previously unidentified antennal lobe (AL) region (outline). (B) The new innervation pattern corresponds to the ‘horn’ (white outline) of the VM6 glomerulus labeled by Rh50+ neurons (orange). One portion of VM6 is strongly Ir8a+ (VM6l), while two other portions show little to no Ir8a expression (VM6m and VM6v, blue outlines). (C) Rh50-Gal4>GFP labels neurons in the sacculus (sac) and antennal coeloconic ac1 sensilla. (D) In the sacculus, all Rh50+ neurons appear to be Ir25a+ (top), and a subset are Ir8a+ (bottom, arrowheads). (E) Top: Rh50+ neurons in the sacculus do not overlap with Ir64a+ neurons. Bottom: there are two distinct populations of Ir8a+ neurons in the sacculus – those that are Ir64a+ and those that are Ir64a- (arrows). The latter likely correspond to Rh50+ neurons. (F) EM reconstructions of VM6 OSNs in a full brain volume (Dorkenwald et al., 2020) reveal three distinct subpopulations. (G) Model of OSN innervation of the VM6 region. VM6 can be subdivided into three OSN populations based on anatomical location in the periphery and chemoreceptor expression: VM6v (blue) OSNs originate in ac1, strongly (s) express Rh50 and Ir25a, and weakly (w) or infrequently express Ir8a; VM6m (orange) neurons originate in the sacculus and have a similar chemoreceptor expression profile to VM6v; VM6l (green) OSNs originate in the sacculus but strongly express Ir8a in addition to Rh50 and Ir25a. Compass: D = dorsal, L = lateral. Scale bars: 20 µm in (A–C) and (F), 10 µm in (D, E). N = 9–11 for (C–E). See also Figure 5—figure supplement 1 and Tables 3 and 4.
Figure 5—figure supplement 1. The new glomerular region labeled by the Ir8a knock-in does not correspond to previously identified posterior glomeruli.
