Figure 1

Birth, clustering and differentiation of larval central brain dopaminergic neurons. (A) Third instar larval stage (L3) brain showing bilaterally symmetrical groups of TH-positive DA neurons clustered according to the position of the cell bodies within the cortex (the number of neurons per cluster is given in parentheses) and the neurite projection patterns. Scale bar: 50 μm. (B-G') Neurite projection patterns. Wild-type cell clones were induced in progenitor cells during early embryogenesis (3 to 7 h after egg laying (AEL)) and analyzed during L3. The clones were labeled with membrane tethered green and red flourescent proteins (both in grey) using the Twin-spot MARCM technique together with the TH-gal4 driver. When possible, neurite projection patterns of the entire cell cluster are shown (B,E,F); otherwise, just one DA neuron as a representative for the cell cluster is produced (C,D). (G,G') The neurite projection pattern (red arrowheads) of DL2b DA neurons (yellow arrows) is shown in two consecutive confocal optical sections. (H) Early L1 brain (24 to 28 h AEL) showing clusters of TH-positive cells (the number of DA neurons per cluster is given in parentheses) Scale bar: 10 μm. (I) Most larval DA neurons in the central brain are born during early neurogenesis between 3 to 13 h AEL. Wild-type cell clones, labeled with the MARCM technique in combination with the TH-gal4 driver, were induced in progenitor cells at different times during development as indicated and analyzed in L3 brains. Images, except for (G,G'), represent Z projections of individual confocal optical sections. AEL, after egg laying; DA, dopaminergic; DL, dorso lateral; DM, dorso medial; L, instar larval stage; MARCM, mosaic analysis with a repressible cell marker; ML, midline; TH, tyrosine hydroxylase.