Transneuronal Dpr12/DIP-δ facilitate compartmentalized dopaminergic innervation of Drosophila mushroom body axons (2021)
Figure 1

Figure 1. Dpr12 is required for full extension of γ-KCs.

(A) Schematic representation of neuron remodeling of γ-KCs and its regulation by the nuclear receptors EcR and UNF. p: axon peduncle; m/v: medial and vertical lobes.

(B) Dynamic expression of Dprs and DIPs during γ-KCs development. Left: Heatmap depicting the relative expression patterns of Dprs and DIPs in γ-KCs during development. Middle: Magenta intensity depicts the peak expression of each gene during development relative to other Dprs and DIPs. Right: Expression change of Dprs and DIPs while knocking down the UNF transcription factor compared to WT γ-KCs. Dprs highlighted in bold were tested in the RNAi mini-screen (Figure EV1).

(C-N) Confocal z-projections of the indicated genotypes and age, labeled with membrane bound GFP (mCD8-GFP; CD8) driven by the γ-specific Gal4 driver GMR71G10-Gal4 (γ-Gal4). While γ-axons of control flies project through the entire lobe (C is the RNAi control; n=12/12, E; is the tsCRISPR control; n=14/14), knockdown of dpr12 by RNAi (D; n=12/12) or knockout by tsCRISPR (F; n=14/14) resulted in short axons. At L3, γ-axons in dpr12∆50-81 homozygotus mutant animals (K; n=20/20) resemble WT γ-axons (G; n=20/20). At 48hr APF, γ-axons normally re-extend to form the adult lobe (H; n=12/12). dpr12∆50-81 γ-axons (L; n=14/14) fail to extend to the end of the lobe. This defect persists to adult (I; n=11/11 vs. M; n=18/18). Expressing a UAS-Dpr12 transgene within γ-KCs in dpr12∆50-81 homozygote mutant animals rescued the axon regrowth defect (N; n=23/24, J; n=14/14).

The adult γ-lobe and α/β lobes are outlined in (C, D) in yellow and orange, respectively, for clarity. Asterisks demarcate the distal part of the lobe. Green and white indicate mCD8-GFP. Magenta represents FasII staining. Scale bar is 20 µm.

(O) Quantification of the regrowth defects in I, M and N. The z-projections were blindly classified into four classes of regrowth defect severity, see Figure EV1D for examples. Significance was calculated by Kruskal-Wallis test followed by a Mann-Whitney post-hoc test; ***p<0.001.

(P) Models based on hemibrain EM-traces (Scheffer et al., 2020) of adult γ-KCs (representative neurons shown in green), in relation to either selected PAM-DANs (left; red and orange) or MBONs (right; cyan and blue) targeting the γ4 and γ5 zones. Note that the cell body of the γ4-MBON is located in the contralateral hemisphere. The MB neuropil is shown in grey. See methods for additional details.

(Q) Schematic representation of the adult MB. The bundled γ-KCs form the γ-lobe (an example of a single γ-KC is depicted in green). The γ1-γ5 zones are defined by stereotyped and tiled innervations of the γ-lobe by dopaminergic neurons (DANs; examples of DANs targeting the γ4 and γ5 zones are depicted in red and orange, respectively) and MB output neurons (MBONs; an example of the γ4>γ1γ2 MBON innervation is shown in cyan to match the schematics in Figure 7E-F; note that its cell body and innervations are located in contralateral hemispheres). Black dashed line represents the midline. Magenta represents typical FasII staining (which stains the α/β lobes and the γ-lobe but not the α'/β' lobes).