Fig. 4. brat mutant clones comprise an excessive number of neural progenitor cells. brat¹¹ MARCM clones positively labelled with CD8::GFP (white) and immunostained as indicated for each panel. The outline of GFP-labelled cellular masses of mutant clones are indicated with dots when GFP label is omitted for clarity. GFP-labelled mutant clones appear heterogeneous in size. (A,B) Most cells express cyclin E (A) and numerous cells are engaged in mitosis (B, magenta, E, yellow). (C-E) In contrast to heterozygous wild-type tissues that surround clones, the majority of brat mutant cells show expression of markers characteristic of neural progenitors: nuclear Grh (C,C'; blue) and cortical Mira (E, magenta). Only very few nuclei express Pros (C', arrowheads) and Elav (D, arrowheads). This apparent deficit in neural differentiation of brat mutant cells is also revealed by the absence of axonal processes. Scale bar, 50 µm; genotype as in Fig. 2.