Pictures of WL3 stage WT and expanded DAL lineages with pros knock‐down at different temperatures (single optical sections; lineages outlined with dotted lines) and schematic of expanded ones with same coding as in (B).
Quantification of Dpn+ and Dpn− cells in DAL lineages in the conditions depicted in (A); histograms represent the mean (n = 4–12 CNSs; details in source data) and error bars SEM.
Pictures of WL3 stage WT versus expanded DAL lineages with pros knock‐down to levels compatible with the production of numerous supernumerary neurons (single optical sections; lineages outlined with dotted lines in split magenta and blue channels).
Pictures of adult WT and prosRNAi‐expressing DALam lineages in animals reared at 29°C (maximum intensity projections).
In adult DAL lineages (outlined with dashed lines), like in control, prosRNAi
LH knock‐down never leads to EdU‐ or Dpn‐positive cells; in contrast, with prosRNAi
KK knock‐down a few EdU+ cells can be observed (boxed area shown at higher magnification in inset) as well as numerous Dpn+ cells, some of which aberrantly retain the early temporal marker Chinmo (maximum intensity projections).
Quantification of Dpn+ cells in WT and expanded DAL lineages at various timepoints after WPP stage; histograms represent the mean (n = 6–34 CNSs; details in source data) and error bars SEM.
Schematic representation of expression of key transcription factors (color‐coded) in type I neural lineages (NSCs, GMCs, and neurons). Top row: Following asymmetric localization during NSC metaphase, Pros (blue) is segregated exclusively into the GMC daughter, in which Pros translocates into the nucleus promoting a differentiative division to generate two neurons; at pupal stages, preceding NSC terminal division, Pros translocates into the NSC nucleus, which leads to differentiation of the NSC itself and thus absence of NSCs in the adult central brain. Middle row: In conditions of pros attenuation (by GAL4‐dependent RNAi, which can be exacerbated by increasing the temperature from 18 to 29°C; by overexpression of Dcr‐2; and/or filtering en‐GAL4 through the strong act5C promoter with the FLP‐out method that also results in permanent cell labeling), GMCs can revert back to NSCs (purple square arrow) and the frequency with which this occurs is inversely proportional to Pros levels (black and gray triangles); accompanying GMC reversal is the production of supernumerary NSCs and supernumerary neurons (magenta and blue shapes, respectively) up to the point when absence of Pros is incompatible with neuronal differentiation, at least in some lineages (blue shape tapering off in parallel with Pros levels approximating zero). Bottom row: Illustration of how Pros levels can direct cellular decisions in type I lineages, from WT with a single NSC, to formation of non‐tumorigenic supernumerary cells, to tumor formation.
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