Figure 5.

Ab and let-7 are key factors required cell autonomously for MB neuron differentiation. (A, B) At the L3 larval stage induction of clones in MBs resulted in appearance of parental control and let-7 single/double GFP marked α′/β′ neurons in (Control, hsFlp UAS CD8GFP; tubGal80 FRT 40A/FRT 40A; tubGal4/+ and hsFlp UAS CD8GFP; tubGal80 FRT 40A/let-7 miR-125 FRT 40A; tubGal4/P{W8, let-7-C^Δlet-7}). (C) While control and let-7 neurons differentiate into α′/β′ neurons, which is in agreement with the time of clonal induction, a part of ab neurons project into α/β neurons which is distinguished here due to co-localization of GFP marked ab neurons with an α/β neuron marker Fas II. (D) The frequency of occurrences of different clonal MB neuronal subtypes induced at L3 (see also Supplementary Table 8). (E) Contrarily, ab loss of function, due to clonal induction at the pupal stage when α/β neurons are specified (12 h APF), is nonessential for differentiation of these neurons; all clonal neurons correctly send their axonal projections to form α/β lobes. (F) The frequency of the properly formed α/β neurons induced at pupal stage (see also Supplementary Table 8). (G-J) let-7 deficiency affects α/β neuron differentiation. While some let-7 neurons form correct axonal projections (G), most of them exhibit random walk and midline crossing (H), projection into α′/β′ lobe (I), and precocious termination (J). Blue outlines α/β lobes, yellow arrows point neuronal defects.