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Tiling of the Drosophila epidermis by multidendritic sensory neurons

Wesley B. Grueber, Lily Y. Jan and Yuh Nung Jan*

Howard Hughes Medical Institute, Departments of Physiology and Biochemistry, 533 Parnassus Avenue, Room U226, Box 0725, University of California, San Francisco, San Francisco, CA 94143-0725, USA



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  		Fig. 1. Identification of peripheral dendritic arborization (da) neurons using the MARCM system. (A) A diagram of the Drosophila abdominal peripheral nervous system modified from Brewster and Bodmer, and Merritt and Whitington (Brewster and Bodmer, 1995Go; Merritt and Whitington, 1995Go). da neurons, red diamonds; external sensory neurons, yellow circles; other multidendritic neurons, green triangles; chordotonal organs, blue rectangles. The lateral oenocytes are shown as gray ovals. We have designated names for the dorsal cluster neurons on the basis of their typical ventral to dorsal cell body position. (B) Gal4 109(2)80-driven mCD8::GFP in third instar md neurons, oenocytes and chordotonal organs. An arrow indicates the position of the neuron labeled in C. (C; top) Components of the MARCM system used to characterize the normal morphologies of da neurons. (Bottom) A mitotic clone of ddaD. (Its location within a typical hemisegment is indicated by a white arrow in B.) (D) Computer tracings of the branching patterns of the four classes of neurons. Representative main branches and side branches from single neurons in each class are shown. These branches are not oriented according to larval axes. Dorsal is up and anterior to the left in panels A-C. Scale bars, 100 µm (B); 50 µm (D).

 


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  		Fig. 2. Identities and dendritic morphologies of class I neurons. (A) Locations and territories of class I neurons in a schematized hemisegment of the abdominal PNS. Four cells were used to construct maps of each neuron in this and subsequent figures. Included in this class are ddaD (B; n=8), ddaE (C; n=10) and vpda (D; n=12). (B-D) Dendritic morphologies of ddaD (B), ddaE (C) and vpda (D). The name of the neuron in each confocal image is shaded the same color as its corresponding cell body and dendritic branch terminals in the PNS schematic (A). Axons are indicated by small arrowheads. Epidermal cells labeled by activity of the ELAV-Gal4 construct are indicated by a large arrowhead. Dorsal is up and anterior is to the left. Scale bars, 50 µm.

 


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  		Fig. 3. Identities and dendritic morphologies of class II neurons. (A) Locations and dendritic territories of class II neurons in a schematized hemisegment of the abdominal PNS. Included in this class are ddaB (B; n=11), ldaA (C; n=16), vdaA (D; n=6) and vdaC (E; n=8). (B-E) Morphologies of individual class II neurons. The name of the neuron in each confocal image is shaded the same color as its corresponding cell body and dendritic branch terminals in the PNS schematic (A). Axons are indicated by small arrowheads. A labeled epidermal cell in E is indicated by a large arrowhead. Dorsal is up and anterior is to the left. Scale bars, 50 µm.

 


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  		Fig. 4. Identities and dendritic morphologies of class III neurons. (A) Locations and dendritic territories of class III neurons in a schematized hemisegment of the abdominal PNS. Included in this class are ddaF (B; n=24), ddaA (C; n=13), ldaB (D; n=23), v’pda (E; n=22) and vdaD (F; n=12). (B-F) Morphologies of individual class III neurons. Axons are indicated by small arrowheads. The name of the neuron in each confocal image is shaded the same color as its corresponding cell body and dendritic branch terminals in the PNS schematic (A). The white arrow in B indicates the position of the segment border. To the left of this arrow, dendrites mix with a ddaE clone in the next anterior segment. An arrow in E indicates the position of the v’pda cell body between a labeled es neuron (above) and an epidermal cell (below). (G) Double labeling with mAB 22C10 to label axons and dendrites and anti-mCD8 to label a class III clone. Note the extensive spiked protrusions extending from primary trunks that are labeled by 22C10 (which labels a microtubule-binding protein) (Hummel et al., 2000Go). Dorsal is up and anterior is to the left. Scale bars, 50 µm.

 


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  		Fig. 5. Identities and dendritic morphologies of class IV neurons. (A) Locations and dendritic territories of class IV neurons in a schematized hemisegment of the abdominal PNS. Included in this class are ddaC (B; n=63), v’ada (C; n=46) and vdaB (D; n=29). Overlap of terminals in the map represents cell-to-cell variation in field size rather than a violation of tiling (see Results). (B-D) Morphologies of individual class IV neurons. Axons are marked by small arrowheads. The name of the neuron in each confocal image is shaded the same color as its corresponding cell body and dendritic branch terminals in the PNS schematic (A). The arbor of each cell covers an entire region of the body wall from the anterior to posterior segment boundaries (arrows in B and D). Dorsal is up and anterior is to the left. Scale bars, 50 µm.

 


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  		Fig. 6. Dendrites in different classes overlap extensively. (A,A') A confocal image of v’ada (class IV; green in A') and ldaA (class II; red in A') which were dually labeled using the MARCM system. (B,B') Branches belonging to the dorsal cluster neurons ddaC (class IV; green in B') and ddaF (class III; red in B') typically extend along the same path. The main dendritic trunks of each neuron emerge at the bottom of the panel (the cell bodies are just out of view). The dendrites of ddaC terminate near the dorsal midline (arrow), but those of ddaF extend into the contralateral hemisegment. Dorsal is up and anterior is to the left. Scale bars, 50 µm.

 


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  		Fig. 7. Dendrites of adjacent class II (A), III (B,C) and IV (D,E) neurons do not overlap. (A,A') Dual labeling of the class II neurons vdaA and vdaC. White arrows indicate labeling of motoneurons, and a white arrowhead indicates the axons of vdaA and vdaC. (B,C) Lack of overlap between dendrites of class III neurons (n=6). Examples of dendritic exclusion between dorsal cluster neurons (ddaA and ddaF; B) and ventral neurons (v’pda and vdaD; C) are shown. The confocal images (B,C) are color coded (B',C') to identify the individual branches of each neuron. A white arrow in B' shows an example of avoidance between dendrites of the same neuron (isoneuronal avoidance). Black arrows in B' and C' show cases in which a dendrite from one cell terminates its growth before crossing the dendrite of an adjacent cell. A black arrowhead in B' shows a dendrite that turns away from the dendrites of an adjacent cell. (D,E) Class IV dendrites from adjacent neurons form non-overlapping boundaries (n=21). Examples of dendritic exclusion between v’ada and vdaB (D; dendrites are colored in D') and ddaC and v’ada segmental homologs (E; dendrites are colored in E’) are shown. A white arrow in D shows the axon of v’ada extending to the CNS. White arrowheads in D and E show points of apparent dendritic contact and/or crossing. In these cases, the cell of origin of each dendrite branch was difficult to determine unambiguously. A black arrow in E' shows the location of the segment border. Dorsal is up and anterior is to the left in all panels. Scale bars, 50 µm.

 


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  		Fig. 8. Quantification of dendritic crossing among different cell pairs within a randomly chosen 104 µm2 area where the territories of two adjacent cells meet. Overlap was not quantified for class I or II dendrites because we did not observe co-labelings of adjacent neurons (see Results). The means±s.d. are shown. The numbers above each bar indicate n values.

 


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  		Fig. 9. Tiling in stanE59 (fmiE59) and seq22 mutant neurons. (A) MARCM scheme for producing stanE59 (fmiE59) mutant clones. ‘UAS’ indicates a UAS-mCD8::GFP insertion. For producing seq clones FRT42D was used in place of FRTG13. (B,C) stanE59/stanE59 (fmiE59/fmiE59) segmental homologs. The dendrites of these ddaC neurons stop at the lateral margin (arrow in B) where they meet the dendrites of an adjacent class IV neuron. (C,C') A high-magnification view of the region surrounding the arrowhead in B, where dendrites show normal self-avoidance and are excluded from the territory of a segmental homolog. (D) Dendritic overextension phenotype seen in a stan (fmi) mutant ddaC neuron. A white arrowhead identifies the cell body. The white arrows identify a branch extending beyond the segment border along the dorsal midline. The dorsal and ventral boundaries of the cell are delineated by white lines. (E) Dendritic overextension in the ventral neuron, vdaB. A white arrowhead identifies the cell body. Arrows follow the dorsal and ventral extensions. The remaining branches innervate their normal territory in the ventral body wall. (F,F') Dendritic field formation by seq22/seq22 type IV neurons appears normal. As shown here, dendrites of v’ada segmental homologs (traced in red and green in F') avoid each other’s territories and form normal boundaries at the segment border (large star). In some areas near the segment border, the cell of origin of individual dendrites is difficult to determine (small star), although obvious dendrite crossing was not observed. Dorsal is up and anterior is to the left. Scale bar, 25 µm (C,C'); 50 µm (B,F,F'); 100 µm (D,E).

 

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