Figure 9. Embryonic progeny of NB2-3 are developmentally arrested during larval life, but differentiate during metamorphosis to be leg motor neurons.
(A, E) R77B09AD-R28H10DBD (A) and VT006878 (E) expression in T2 hemisegments from a late stage larva shown. EDU (red) labels all of the postembryonic neurons but not NB2-3 progeny (outlined with dashed lines); hence outlined cells are born embryonically. (B) None of these embryonic-born cells marked by R77B09AD-R28H10DBD express vGLUT (indicator of mature motor neurons) with the exception of a motor neuron in the T1 segment (arrow). VT006878 marked neurons do not express vGLUT either (not shown). (D) R77B09 (red) and VT006878-LexA (green) mark ventral and dorsal embryonic progeny of NB2-3, respectively. Transverse view shown on the right; dorsal up. (C, E) T2 lineage clones, which are generated via R77B09AD-R28H10DBD(C) and VT006878 (E) are induced in an early embryo and visualized in the late-stage larva. Like in the embryo (see Figure 5), axons of NB2-3 embryonic progeny split into two bundles after exiting the CNS. One of these bundles extends toward the leg disc (arrowheads). (E) VT006878 expression in T2-T3 segments in the larval CNS. (H-L) Immortalization of VT006878 expression visualizes these neurons in the pupal (H) and adult nerve cord (I) and innervation pattern of their axons in the adult leg (J-L). (J) VT006878 marked neurons innervate muscles in the coxa, trochanter, and femur parts of the leg but not the tibia. High magnification views from coxa (K) and trochanter (L).