|Feature type||allele||Associated gene||Dmel\cnn|
|Map ( GBrowse )|
What does this section display?
This section contains items that were added to this record for each release. It currently only tracks new links between this FlyBase report and other FlyBase data classes (e.g. genes, references, stocks) or controlled vocabulary terms (e.g. GO, anatomy terms).
What does this section not display?
This section does not currently display links that were removed or gene model changes.
Click the icon below to subscribe to this FlyBase record and receive updates automatically through your feed reader.
|All updates||Click here to see a list of all updates to this record from FB2010_08 and on.|
|Nature of the Allele|
|Mutations Mapped to the Genome|
|Associated Sequence Data|
|Nature of the lesion|
Nucleotide substitution: C316T. Amino acid replacement: Q106@. The predicted truncated protein produced lacks all three leucine zipper motifs.
Amino acid replacement: Q106@. Nucleotide substitution: CAG codon is replaced by a UAG codon. Contains an stop codon within the amino terminal of the coding region.
|Phenotype Manifest In|
centrosome & male germline stem cell
embryonic cortex & actin filament
male germline stem cell & centrosome
male germline stem cell & spindle
During the early larval stage, cnn[HK21] mutants show no defects in photoreceptor differentiation or pattern formation. However, from the mid-pupal (50%) developmental stage, the cnn[HK21] mutation causes acetylated microtubule bundle mispositioning and apical domain localisation defects.
Only 37% of testis somatic cyst stem cells show repositioning of the mitotic spindle during anaphase in cnn[mfs3]/cnn[HK21] males compared to 78% of cases in heterozygous controls.
Mutant embryos have a reduced number of pole cells compared to controls and the pole cells that do form often have greatly reduced germ plasm.
In mutant spermatids, the proximal centriole-like structure forms, though the gamma-tubulin collars of the centrioles are largely reduced and almost absent or show an abnormal localization.
cnn[HK21] mutants have an increased number of brain neuroblasts, and 12-13% of the metaphase neuroblasts show aberrant spindle orientation orthogonal to the apical/basal cortical polarity axis. This subset of neuroblasts showing aberrant spindle orientation always generate equal-sized siblings that both assume neuroblast identity. Single cnn[HK21] neuroblast clones often give rise to two or more neuroblast sibling cells, but never two basal ganglion mother cells.
Embryogenesis fails during the first few cleavage divisions in mutant animals, and most embryos examined show no signs of development.
cnn[HK21] embryos exhibit a 'linked spindles' phenotype, indicative of defective cleavage furrows.
Third-instar larval neuroblasts from cnn[HK21] mutants exhibit mitotic spindles with broad poles, lacking astral microtubules.
Anaphase onset is considerably delayed in cnn[HK21] mutants. cnn[HK21] mutants normally suffer little aneuploidy (~1%) and survive to adulthood.
In embryos laid by cnn[HK21] homozygous females, the centrioles are associated with appreciable amounts of PCM, but are often not properly centered within it. The centrioles appear to be constantly nucleating PCM but seem unable to maintain their connection to it. The centrioles often exhibit irregular, stochastic movements, leaving a trail of PCM behind them as they move away. As a result of this behavior, the centrioles in cnn[HK21] embryos often lose their attachment to the nuclear envelope in interphase and to the spindle poles in mitosis. The centrosomes in cnn[HK21] embryos organise astral microtubule arrays but seem unable to maintain their connection with them. when the embryos enter mitosis, many nuclei are not associated with centrioles, and anastral spindles assemble around the mitotic chromatin. Many nuclei, however, are close enough to a centriole for the astral microtubules to contribute to spindle assembly. However, these centrioles fail to maintain their position at the spindle pole and either wander around within the spindle or lose their connection to the spindle altogether. The dramatic mitotic defects in cnn[HK21] mutant embryos results from the failure of the centrioles to maintain a stable connection to the PCM and microtubules that they organise. In most cnn[HK21] neuroblasts, no prominent MTOC is detectable before nuclear envelope breakdown, and spindle assembly occurs largely by an acentrosomal pathway. Nonetheless, approximately 95 of cnn[HK21] neuroblasts ultimately divide asymmetrically, whereas approximately 4% divide symmetrically and 1% fail in cytokinesis. Although this failure rate is modest, it is still significantly higher than in wild-type.
For homozygous mutant male germline stem cells where one of the two centrosomes is positioned next to the hub, it is essentially random whether the mother or daughter centrosome stays next to the hub (in contrast to wild type where the daughter centrosome migrates away from the hub).
In mutant males, mitotic spindles are not oriented towards the hub in about 30% of dividing germline stem cells (GSCs) examined (in contrast to wild-type males where the mitotic spindles of the GSCs are always oriented perpendicular to the hub-GSC interface). In an additional 10-20% of mutant GSCs, the spindles are properly oriented, but the proximal spindle pole is no longer closely associated with the cell cortex at the hub-GSC interface and the entire spindle is displaced away from the hub. The frequency of spindle orientation defects is highest in metaphase. Interphase centrosome positioning is partially randomised in the mutant GSCs; in more than 35% of mutant GSCs with duplicated centrosomes, neither centrosome is positioned next to the hub (in wild-type male GSCs with duplicated centrosomes, one centrosome remains adjacent to the hub). Dividing GSCs with misoriented or detached spindles, which lose attachment to the hub are seen. Hub size is not significantly different in mutant males compared to wild type. The number of germ cells associated with the hub is increased 20-30% in homozygous males, from an average of 8.94 GSCs per hub in wild type to 11.89 GSCs per hub in homozygotes. In mutant testes with many stem cells, GSCs appear crowded around the hub and often seem attached to the hub by only a small region of cell cortex. The number of germ cells associated with the hub is increased 20-30% in homozygous males, from an average of 8.94 GSCs per hub in wild type to 10.69 GSCs per hub in cnnHK21/cnnmfs3 males. In some cases in cnnHK21/cnnmfs3 testes, a GSC divides and the two daughter cells remain in contact with the hub (this is not observed in the wild type).
Adult lies have black dots on their wings. Mitotic figures from mutant larval brains have no (cnn staining) centrosomes at the spindle poles. Mutant spindles appear meiotic in character, with the smaller forth chromosomes migrating to the spindle poles precociously. Despite the absence of mitotic centrosome centrioles with normal morphology can be found. The spindle microtubules appear to assemble outward from the chromosomes. Astral microtubules are absent at prophase. cnnHK21 neuroblasts are found to be oriented improperly approximately 22% of the time.
Homozygous females produce embryos that arrest prior to cellularisation. Embryos derived from cnnHK21/Df(2R)cnn females have severe defects in nuclear division and distribution. The embryos never achieve cellularisation.
cnnHK21 embryos show a lack of spindle pole localisation of centrosome associated antigens Cp190 and γTub23C in a variable manner, suggesting that the Microtubule Organising Centres are at least structurally and functionally impaired, or possibly missing altogether. Embryos from cnnE2/cnnHK21 mothers exhibit an abnormal and disorganised spatial arrangement of nuclei during syncitial divisions, becoming increasingly severe during later divisions. This leads to a cessation of development before formation of a cellular blastoderm. In contrast to wild-type, embryos from cnnHK21 mothers show an unstructured cortical microfilament organisation during syncitial development. Syncitial embryos from cnnE2/cnnHK21 mothers, show abnormally shaped mitotic spindles that are characteristically squat with ill-defined poles. During interphase and prophase, a variable number (as opposed to strictly two in wild type) of spread out and less discrete astral microtubule-like structures are seen, despite having no γTub23C localising nucleating core.
Eggs derived from homozygous females initiate development and cytoplasmic clearing occurs in a narrow zone around the egg periphery (in wild-type embryos this process is coupled to the arrival of the nuclei at the periphery). The eggs do not seem to develop beyond this stage; pole cells are not formed and cellularisation does not occur. However, about two hours after cytoplasmic clearing, the egg periphery starts to show local contractions, in what might be an attempt at gastrulation. These contractions eventually lead to eggs which typically have one or two condensed yolk balls surrounded by more transparent cytoplasm.
maternal-effect lethal Homozygous females lay eggs in which a narrow halo of clear cytoplasm appears around the time when nuclei would be expected to migrate to the egg periphery, but no cellularization takes place. female-sterile
cnn[+]/cnnHK21 is an enhancer of partially lethal - majority die | maternal effect phenotype of Df(2L)Fs(2)Ket-RX32/Cenf04787
|Phenotype Manifest In|
A cnn[HK21] heterozygous background dominantly enhances the rough eye phenotype found upon expression of baz[Scer\UAS.cKa] by Scer\GAL4[GMR.PF].
Presence of a single copy of cnn[HK21] enhances the rate of embryo hatch failure from Cen[f04787]/Df(2L)Fs(2)Ket-RX32 mothers.
mad2[G6595] cnn[HK21] double mutants exhibit a shortened prometaphase with an increase in aneuploidy compared to both single mutants and are larval lethal. BubR1[A1204K.PR] cnn[HK21] double mutants exhibit low aneuploid rates as in the single mutants and survive to adulthood. Double mutants of BubR1[KEN.T:Disc\RFP-mRFP] and cnn[HK21] are pupal lethal with aneuploidy averaging 15%.
cnn[HK21];msd1[ex51] double mutants are homozygous lethal, dying at an early pupal stage. cnn[HK21];msd1[ex51] mutants show "metaphase-like" cells with weak, unorganized microtubule arrays; very few robust spindles are observed. An increased mitotic index is observed in these double mutants, greater than the increase seen in either cnn[HK21] or msd1[ex51] single mutants, and a dramatic increase in metaphase-to-anaphase ratio. Microtubule nucleation around chromatin in cnn[HK21];msd1[ex51] mutants is still observed, similar to that seen during prometaphase in cnn[HK21] mutants, suggesting that nucleation of microtubules from around mitotic chromatin is insufficient for viability.
mad2[G6595] cnn[HK21] double mutants exhibit a severely delayed sindle assembly pathway, resulting in a higher mitotic index and a broad peak anaphase onset time of 8-16 minutes. Larval brains of mad2[G6595] cnn[HK21] double mutants have a very high incidence of polyploidy and mad2[G6595] cnn[HK21] individuals die as early pupae.
|Complementation & Rescue Data|
|Fails to complement|
|Not rescued by|
Expression of cnn[PA.Scer\UAS.P\T.T:Avic\GFP] under the control of Scer\GAL4[nos.UTR.T:Hsim\VP16] does not rescue the cnn[HK21] mutant phenotype; none of the eggs produced by cnn[HK21] females expressing cnn[PA.Scer\UAS.P\T.T:Avic\GFP] under the control of Scer\GAL4[nos.UTR.T:Hsim\VP16] hatch.
|Stocks ( 2 )|
|Notes on Origin|
|External Crossreferences & Linkouts|
|Synonyms & Secondary IDs ( 9 )|
(Christensen and Cook, 2007.3.22, Christensen and Cook, 2007.3.22, Christensen and Cook, 2007.5.8, Yamashita et al., 2007, Yamashita et al., 2007, Lee et al., 2006, Slack et al., 2007, Blachon et al., 2009, Cabernard and Doe, 2009, Lucas and Raff, 2007, Rahmani et al., 2009, Cheng et al., 2011, Lerit and Gavis, 2011)
|Secondary FlyBase IDs|
|References ( 27 )|
|Generate a list of|
|List References by type|
|Recent research papers ( 3 )|