Fig. 1. Mutations in the dlkb1 gene disrupt spindle organization of both NBs and GMCs. (A) Map of the Drosophila lkb1 (dlkb1) gene and its genomic region. P[dlkb1⁺] designates the genomic fragment that rescues both the lethality and the cytological defects associated with the dlkb1 mutation. Black boxes correspond to protein-coding exons, and the arrows indicate the direction of transcription. The positions of the stop codons causing the dlkb1³¹⁵ and dlkb1⁷ mutations are indicated by vertical lines. (B) Mitotic spindle morphology of NBs and GMCs from wild-type (wt) and dlkb1 brains. Cells were stained for tubulin (Tub, green) and DNA (blue). (C) Spindle morphology of wild-type (wt), dlkb1, asl,and asl dlkb1 metaphases stained for tubulin (green), DNA (blue) and Centrosomin (red). Note that the spindle density in asl dlkb1 double mutants is substantially lower than in asl single mutants. Scale bar (all panels): 5 µm.