|Feature type||allele||Associated gene||Dmel\asl|
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|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
|Phenotype Manifest In|
anaphase & condensed nuclear chromosome
larval brain & ganglion mother cell
larval brain & ganglion mother cell & aster
larval brain & ganglion mother cell & centrosome
larval brain & neuroblast
mitosis & nuclear chromosome
neuroblast & nucleus
spermatocyte & aster
The anastral mitotic spindles have a microtubule density similar to that of wild type in asl2 larval brains. The spindles of mutant ganglion mother cells are morphologically indistinguishable from wild type. The average length of ganglion mother cell and neuroblast spindles in homozygous larval brains is similar to that of wild type.
Mutant neuroblasts show robust chromatin-mediated microtubule nucleation and spindle assembly producing fairly normal spindles during mitosis. Spindles poles emerge from a disorganised microtubule array near the chromosomes that focusses as the spindle lengthens. Spindles do not rotate during formation, always forming along the initial pole separation axis, but do rotate during metaphase. Consecutive divisions in the mutants usually produce adjacent or near-adjacent daughters, as in wild type. In a few cases, spindles form parallel to the ganglion mother cell cap, these neuroblasts divide symmetrically.
The mitotic index and frequencies of metaphase and anaphase figures in homozygous and asl2/asl3 larval brains is comparable to wild type. 4-5% of anaphases have lagging chromosomes. A small fraction of metaphases appear to be polyploid; 5-6% hyperploid and 2.6-2.8% tetraploid metaphases are seen. Homozygous and asl2/asl3 larval neuroblasts lack functional centrosomes and are completely devoid of astral microtubules. However, they form central spindles that are indistinguishable from wild type. The central spindle is tightly associated with the nascent ganglion mother cell nucleus, which is in turn closely apposed to the polar cortex, as occurs in wild-type cells. However, wild-type and mutant telophases differ in the positioning of the neuroblast (NB) nucleus; in wild-type, the NB nucleus lies very close to the central spindle but is separated from the polar cortex by a large astral array of microtubules, however the situation is reversed in mutant telophases; the NB nucleus is usually disconnected from the central spindle and located much closer to the polar cortex than in wild type.
Neuroblasts in mutant larval brains lack functional centrosomes and astral microtubules, but have well-focused spindle poles. In homozygous testes, telophases show a morphologically normal central spindle and cytokinesis occurs normally.
Lethality acts at the larval/pupal boundary. Prophase neuroblasts are completely devoid of centrosomes and asters, however a bipolar spindle does form and generates a normal central spindle in anaphase. Chromosome segregation and cytokinesis appear to be normal. Mitosis in GMCs reveals an absence of centrosomes and prophase asters.
|Phenotype Manifest In|
The microtubule density of mitotic spindles in lkb1315 asl2 double mutant larval brains is similar to that seen in lkb1315 single mutants.
|Complementation & Rescue Data|
|Fails to complement|
|Stocks ( 0 )|
|Notes on Origin|
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 1 )|
|Secondary FlyBase IDs|
|References ( 9 )|