Figure 2. Sister hemilineage distinctions.

(A–R) Hemilineage morphology is revealed by pseudo-coloring N^on/A neurons green and N^off/B neurons magenta based on the Notch state (judged from notch RNAi phenotypes). For the seven Vnd lineages composed of dual hemilineages (A–G), representative single-cell clones of A or B neurons were assembled to create synthetic NB clones with sister hemilineages in distinct colors. For the 11 unpaired Vnd hemlineages (H–R), the full pattern was shown by merging the first larval-born neuron with its accompanying NB clone and then pseudo-coloring the merged clone according to A/B fate. (S–X’’) Full-size NB clones (orange) overlaid with both A (green) and B (magenta) hemilineage masks (S–X) or either B (S’–X’) or A (S’’–X’’) hemilineage mask, to examine the hemilineage-structure correspondence in dual-hemilineage NB clones (except SMPp&v1 with widely separate A/B cell body clusters). Composite confocal images viewed from various angles (x, y, and z coordinates indicated above) demonstrate distinct hemilineage-specific neurite fascicles (indicated with green/magenta arrows), extending out of fully or partially separate A and B cell body clusters, in six of the seven Vnd lineages (S–W’’). Only the LALv1 lineage has a mixed cell body region that extends a single neurite bundle projecting posteriorly before dividing into multiple fascicles (X–X’’).

Figure 2—figure supplement 1. Notch-dependent sister hemilineage projections in seven Vnd lineages.

(A) Schematic illustration showing how a conditional GAL4 driver can be irreversibly activated in random type I NBs (through a cascade of pattered recombinase activities) at the timing of interest (controlled by heat shock). The reconstituted ubiquitous GAL4 driver can then activate notch RNAi in addition to the reporter continuously in a lineage-restricted manner. (B–H) Representation of distinct sister hemilineages (N^on: green, N^off: red) reconstituted through merging the identified neuron types of distinct Notch states separately in the standard fly brain template (grey). The Notch states were determined based on phenotypes shown in [B’] to [H’]. (B’–H’) Representative notch-RNAi NB clones (green) in nc82-counterstained adult fly brains (blue). Note persistence of only a half pattern (corresponding to the red N^off hemilineage shown in [B] to [H]) in the labeled notch-RNAi NB clones. Multiple notch-RNAi NB clones could coexist; and some bilaterally symmetrical neurons with midline crossing existed as background clones in almost all samples.