Oogenesis is profoundly disturbed in hts1/hts10089 mutants.
hts1/hts10089 mutant ovaries contain numerous aborted egg chambers that lack ring canals and a clearly differentiated oocyte and never enter vitellogenesis.
Young, 1-4 day old hts1/hts10089 mutant females expressing two copies of htsΔ100.αTub84B display a number of egg chambers that are able to complete oogenesis, with most of the resulting eggs (~60%) able to support embryogenesis to at least the larval stage. Ovaries from these females contain developing egg chambers of various stages, and also egg chambers that have arrested prior to vitellogenesis. All egg chambers in these flies contain ring canals, even those that have failed to mature. As these females get older, the aborted egg chambers accumulate in the ovaries, resulting in an overall failure of oogenesis.
hts1/hts10089 mutant females expressing two copies of htsΔ100.αTub84B only rarely (~5%) contain ectopic actin aggregates.
hts1 mutant germline stem cells display misoriented spindles but are well maintained two weeks after clone induction, indicating that the spindle misorientation is not enough to induce apoptosis in these clones.
hts1 mutant germaria have cysts with a maximum of four cystoblasts and lack any structure resembling the fusome.
Many egg chambers from hts1/Df(2R)BSC26 frequently lack a full complement of germ cells.
Gonial cells of hts1/Df(2R)BSC26 testes do not show fusome structures by immunostaining of Klp61F.
In contrast to wild type, many spermatocytes in hts1/Df(2R)BSC26 and hts1/hts10089 mutants contain too many or too few centrosomes.
In contrast to wild type, 6% of meiotic spermatocytes in hts1/hts10089 mutant testes, and 22% of meiotic spermatocytes in hts1/Df(2R)BSC26 mutant testes show spindle abnormalities, including monopolar and multipolar spindles.
The number of cyst divisions are reduced, resulting in egg chambers that contain fewer than 16 cells. Mitotic divisions involving four or more cells require a synchronizing mechanism, which is disrupted in hts1 mutants, leading to egg chambers with cyst cell numbers that are not multiples of 2n. There are no detectable fusome structures in the cysts of hts1 females. Repetitive photobleaching of individual cystocytes in hts1 mutants fails to deplete fluorescence in adjacent cystocytes within the same cyst, indicating that the cysts do not maintain an interconnected ER. This is consistent with previous electron microscopy studies, which show that the membrane component of the fusome is absent in hts1 mutants. Cytoplasmic connectivity is not affected by the hts1 mutation.
Mutant cysts in the female germarium lack a Balbiani body and mitochondrial clusters near presumptive ring canals. Mitochondrial clumps are present around presumptive centrosomes in stem cells.
Homozygous mutant germaria have no central microtubule clusters either in regions 1-2a or region 3, in contrast to control ovaries. Microtubules appear to run along the periphery of individual cyst cells in mutants. The microtubules are stable in the absence of a fusome. Mutant cysts typically appear linear and not rosette shaped. The microtubule network in M phase and early interphase appears normal in mutant ovaries.
hts1 testes lack fusome structures in cysts of mitotically proliferating germ cells near the apical tip of the testis.
Mutation eliminates spectrosomes and fusomes. Germline development prior to stem cell division is normal. Spindle orientation in stem cells is completely randomised: orientation can be perpendicular to or roughly parallel to the germinal axis. Some spindles can be found several micrometers away from the basal cells and cap cells, a situation never seen in wild-type stem cells. Lack of the fusome affects spindle orientation in dividing two-cell cysts, causes morphological defects in the spindles, reduces cystoblast divisions and affects the synchrony of cystocyte divisions within a cyst. The polarised microtubule network within germline cysts is eliminated and intracyst transport of specific RNAs is abolished.
Mutation abolishes the spectrosome in adult ovaries but does not affect the rate of germline stem cell division.
Fusome is lost, oocyte formation is blocked and differential transport is severely compromised.
Clones in the ovariole severely disrupt cyst formation. Ring canals are defective; fail to accumulate actin. In the germaria fusomes in germline cells are completely absent.
Complete loss of fusome in the adult ovary cells. bamΔ86; hts1 ovaries are phenotypically indistinguishable from bamΔ86 ovaries.
Fewer germ-line divisions and reduced transport of cytoplasm.
Fusomal material is absent or greatly reduced in germaria from mutant females. Ring canals still form.
Homozygous females make egg chambers with fewer nurse cells, defective ring canals and abnormal cystocyte membrane structures.
Homozygous females produce egg chambers with less than 15 nurse cells and these egg chambers usually degenerate before completing oogenesis. Most egg chambers lack an oocyte. Ring canals in cysts and egg chambers are reduced in number and have deformed outer rings. Phalloidin staining revealed that the abnormal ring canals were deficient in actin. Homozygotes show reduced viability.