Homozygous larval brain neuroblasts show a high degree of aneuploidy.
Embryos derived from heterozygous females show abnormalities in approximately 20% of mitotic spindles during syncytial divisions. The majority of the defects occur in cycles 1-9. The most frequent defects are anastral (4.89%) and monopolar spindles (6.77%).
Embryos derived from Klp61F07012/+ females carrying Klp61F3YF.Ubi-p63E.T:Hsap\MYC show a higher incidence of spindles with multiple microtubule organising centers during cycles 1-9 than seen in control embryos. The mutant embryos also show "promiscuous microtubules", including microtubule spurs and microtubules interacting between neighbouring spindles, during cycles 11-13. These promiscuous microtubules are seen in metaphase (at a similar level as occurs in embryos derived from Klp61F07012/+ females with no transgene) and also in anaphase (at a significantly increased level than occurs in embryos derived from Klp61F07012/+ females with no transgene).
Klp61F07012 homozygotes and Klp61F07012/Klp61F06836 trans-heterozygotes display larval lethality.
Klp61FUbi-p63E.T:Avic\GFP rescues the lethality of homozygous Klp61F07012 and trans-heterozygous Klp61F07012/Klp61F06836 mutants. The rescued flies are fertile and can be propagated as stable transgenic lines. The rescued embryos display a decrease in the rate of prometaphase-to-metaphase spindle elongation compared with wild type embryos, which leads to a small decrease in subsequent spindle length.
15% of Klp61F07012 mutant spindles are biastral in larval stage brains. The nuclear lamina in monopolar Klp61F07012 cells in larval stage brains show involutions that extend towards centrally located centrosomes. This suggests that the nuclear lamina is directly or indirectly attached to centrosomal material and/or centrosomal asters. Acentrosomal meiotic spermatocytes of Klp61F07012 homozygotes, Klp61F07012/Klp61F06345 transheterozygotes, and Klp61F07012/Df(3L)bab-PG exhibit microtubules, but do not show microtubule asters or detectable spindle structures. Spermatocytes containing centrosomes display a range of spindle defects, classic monopolar spindles are found in less than 10% of spindle structures in Klp61F07012 mutants, substantially lower than the 50-75% frequency found in somatic cells of Klp61F07012 mutants. Most meiotic spindles had characteristics of both monopolar and monastral bipolar spindles, showing microtubules splayed into broad spindle poles that lack detectable γ-tubulin or showing splintered spindle poles with foci of γ-tubulin at the ends of microtubule bundles. Despite the abnormal organisation of microtubules, spermatocytes in telophase show a cytokinetic furrow that divides the spermatocyte unequally, with one daughter receiving most or all of the bivalents and centrosomes. Telophase is also abnormal in that bivalents typically remain paired. Fusiform structures, indicative of a bipolar spindle in wild-type spermatocytes are not detected in Klp61F07012 and Klp61F07012/Klp61Furc-1 transheterozygote spermatocytes. In Klp61F07012 mutant spermatocytes the nuclear lamina shows deep involutions that are occupied by closely apposed centrosomes. The nuclear lamina appears to collapse around bivalents in spermatocytes and form micronuclei, irrespective of the presence or absence of centrosomes. Klp61F07012 meiotic spermatocytes show immunostaining of aggregates that are typically associated with chromatin within micronuclei.
The fusome in Klp61F06345 testes appears to be fragmented.
The brains of homozygous larvae have a reduced frequency of anaphase figures, and an increased frequency of polyploid figures and overcondensed chromosomes compared to wild-type. The brains and imaginal discs are small compared to wild-type in approximately 50% of the larvae. Nearly all homozygous spermatocytes are equal in size and contain equivalent amounts of chromatin. The spermatocytes contain a variable number of centriole pairs, the most common being 0 (35% of spermatocytes), 2 (25% of spermatocytes) and 4 (24% of spermatocytes) centriole pairs, and 10% of spermatocytes contain an odd number of centriole pairs.
Homozygotes and hemizygotes die as late third instar larvae or early pupae. Neuroblasts isolated from third instar homozygous larvae show an increased mitotic index and complete lack of anaphase figures, indicating metaphase arrest. Chromosomes are hypercondensed compared to wild-type, monopolar spindles are seen and highly polyploid cells are common.