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FB2026_01
,
released March 12, 2026
Frameshift mutation, resulting in a truncated protein of 234 amino acids.
Homozygous, lkb1315/Df(3R)urd and lkb1315/lkb17 larvae show identical mitotic defects in the brain. The mutant spindles show an overall microtubule density that is substantially lower than wild type. In approximately 80% of mutant spindles, asters are absent or severely reduced (this is a higher frequency than the 49% of control brains that have absent or severely reduced asters). Most mutant prometaphase and metaphase figures show low densities of both kinetochore and interpolar microtubules. Ana-telophases have central spindles that are thinner than those in controls. Mutant brains show an increase in the relative frequency of metaphase figures with respect to wild type. The mutant brains contain approximately 20% polyploid cells. The frequency of symmetric telophases is higher in the mutant brains than in wild-type controls.
lkb1315/Df(3R)urd larval brain neuroblasts show small asters in both metaphase and ana-telophase figures.
The average length of neuroblast spindles is shorter in lkb1315/Df(3R)urd larval brains compared to wild type. The average length of ganglion mother cell spindles in lkb1315/Df(3R)urd larval brains is similar to that of wild type.
lkb1315/Df(3R)urd larval brain neuroblasts divide more symmetrically than wild-type neuroblasts.
Only 34% of lkb1315/Df(3R)urd larval brain neuroblasts have centrosomes of different sizes at their poles (compared to 88% of wild-type neuroblasts).
The microtubule density of mitotic spindles in lkb1315 asl2 double mutant larval brains is similar to that seen in lkb1315 single mutants.
The spindles of both neuroblasts and ganglion mother cells are much more defective in lkb1315 rapsP62 double mutant brains compared to those of either single mutant. In addition to cells with severely defective spindles, approximately 50% of mitotic figures have barely recognisable spindles. In double mutant metaphases, the microtubule density is extremely low, the spindle poles have a characteristic pointed appearance and the asters are completely absent. Double mutant ana-telophases are also completely devoid of asters and have few and sparse central spindle microtubules, which are never pinched in the middle. The double mutant neuroblast spindles are smaller than in wild type. 90% of the large metaphase figures (likely to be neuroblasts) have equally sized centrosomes in the double mutants.