The reduced male fertility as well as morphological defects in the adult testes (including but not limited to hyperplastic cyst overgrowth) observed in adult males expressing CHES-1-likeScer\UAS.T:Ivir\HA1 under the control of either the Scer\GAL4nos.UTR.T:Hsim\VP16 or the Scer\GAL4bam.T:Hsim\VP16 driver are enhanced to a variable degree by combination with a single copy of bamΔ86.
Expression of dppJF01371 or ptcJF03223, but not ciGD1403, under the control of Scer\GAL4C587 in flies expressing bamhs.PO induced via heat shock in a bamΔ86/bamΔ86 background suppresses the recovery of spectrosome-containing cells at 48 h after heat shock seen in flies expressing bamhs.PO alone in a bamΔ86/bamΔ86 background.
ball2 bamΔ86 double mutant germline cells in the ovary do not form tumours. The double mutant cells are lost from the stem cell niche, with the rate of stem cell loss being similar to that seen in ball2 single mutants. Double mutant germline cells that have been displaced from the niche do not differentiate into germline cysts and they eventually degenerate.
One copy of CSN4N dramatically suppresses the increase in the number of undifferentiated cystoblasts seen in bamz3-2884/bamΔ86 mutants, dramatically increasing the number of differentiated cysts containing a branched fusome and the number of normal egg chambers per ovariole.
One copy of CSN4k08018 dramatically suppresses the increase in the number of undifferentiated cystoblasts seen in bamz3-2884/bamΔ86 mutants, dramatically increasing the number of differentiated cysts containing a branched fusome and the number of normal egg chambers per ovariole.
Expression of CSN4Scer\UAS.P\T.T:Ivir\HA1 under the control of Scer\GAL4nos.PU in a bamΔ86/+ mutant background results in an increase in cystoblast and two cell cyst number in the ovary compared to controls. Germline stem cell number is unaffected.
One copy of CSN5N drastically and significantly enhances the differentiation defect of the bamΔ86/+ mutants. The number of cystoblasts and two cell pairs is significantly increased compared to either heterozygote alone.
udd1 partially suppresses the differentiation defects seen in bamΔ86 mutant female germline cells. Many four- and eight-cell cysts with branched fusomes and ring canals are seen, but mature 16 cell cysts are not observed.
The germarium phenotype of bamΔ86 Df(3R)Exel6198/twin41 bamΔ86 double mutant females is a mixture of a bam mutant phenotype (accumulation of germline stem cell (GSC)-like cells containing a spectrosome) and a twin mutant phenotype (lack of GSCs or lack of germ cells). The phenotype changes over time, with the percentage of bam mutant phenotype decreasing and the percentage of twin mutant phenotype increasing as the flies age. The double mutant GSCs are able to differentiate.
Removal of one copy of bam, through a bamΔ86/+ strongly suppresses the aurB1689 phenotype (from 17% to 4% of eight cell cysts), indicating that the phenotype is caused by the reduction of aurB activity in the cyst and not in the germline stem cell.
3 day old females expressing nosALL.T:Hsap\MYC in a bamΔ86/+ background show a modest but consistent increase in the average number of spectrosome-containing cells per germarium which is accompanied by a statistically significant loss of differentiated cysts. This effect is more pronounced in 20 day old females.
Expression of howL.Scer\UAS under the control of the weak driver Scer\GAL4nos.PG enhances the bamΔ86/+ phenotype, as shown by the fact that 65% of cysts containing 32 spermatocytes, compared to 27% in bamΔ86/+ single mutants.
The delayed differentiation of 16-cell male germline cysts until they are greater than 32-cells/cyst in animals expressing stgScer\UAS.cNa under the control of Scer\GAL4bam.T:Hsim\VP16 is enhanced from 11% to 27% in a bamΔ86/+ mutant background.
The premature differentiation of 8-cell male germline cysts observed in animals expressing trblScer\UAS.P\T.cMa under the control of Scer\GAL4bam.T:Hsim\VP16 is suppressed, from 63% to 10%, in a bamΔ86/+ mutant background, and the frequency of 16-cell cysts is increased from 37% to 87%.
Approximately 80% of stwl95 bamΔ86 double mutant female germaria contain germ cells interconnected by branched fusomes, indicating that cystoblasts have formed and initiated cyst differentiation. On average, 30% of germ cells in these ovaries are in clusters penetrated by branched fusomes.
pum02003 bamΔ86/pum9 bamΔ86 double mutant ovaries have a complex phenotype that is distinct from that of either single mutant. A mixture of apparently undifferentiated cells and overtly polyploid cells is seen. In many cases, the polyploid chromosomes are thick and expanded like nurse cell chromosomes. Occasionally these pseudo-nurse cells are organised within an epithelial layer of follicle cells, like a cyst, although these cysts never contain a full complement of 16 cystocytes. These cysts contain ring canals.
piwi1 ; bamΔ86 double mutant ovarioles have mildly tumorous germaria filled with 50-300 undifferentiated germ cells with no apparent egg chamber development. fs(1)Yb72 ; bamΔ86 double mutant ovaries display the same phenotype as seen in bamΔ86 single mutants. Most germaria are devoid of germ cells in pum1 bamΔ86/pum9 bamΔ86 double mutant females.
In pelo1;bamΔ86 double mutant germaria, germ cells are able to differentiate as cystocytes can form. This is evidenced by branched fusomes, although the morphology of these fusomes is abnormal. However, some germ cells remain undifferentiated, as abnormally enlarged spectrosomes persist. Germ cell differentiation is not rescued when bamΔ86 homozygous mutants are pelo1/+; these germaria also show the rapid loss of GSCs observed in pelo1 germaria.
bamΔ86 ovarian tumor cells transplanted into the dorsal mesoderm of stage 11-12 embryos from oskunspecified mothers can repopulate the ovaries of the resulting adults, forming tumorous ovaries. The fertility of these flies can be rescued by heat shock if the transplanted cells carry bamhs.PO.
mei-P261/Y ; bamΔ86/+ males are completely sterile. Spermatid differentiation fails to progress in these males. mei-P261/mei-P261 ; bamΔ86/+ females show a severe decrease in fertility compared to mei-P261/mei-P261 females, due to an increase in the formation of ovarian tumours and other egg chamber defects. Recombination is also severely decreased in these females. mei-P261/+ ; bamΔ86/+ females have normal fertility.
bgcnQS2; bamΔ86 double mutant germ cells also are interconnected and undergo S phase in synchrony. The double mutant germ cells, just like germ cells in either single mutant behave as amplifying primary or secondary spermatogonial cells, and not as stem cells, indicating that bam and bgcn are not partially redundant with each other.
Expression of Dsim\bambam.T:Avic\GFP-YFP.Venus partially restores fertility of the otherwise sterile bamΔ59/bamΔ86 females. The ovaries of the rescue females show multiple morphological defects that accumulate with age (loss of germline stem cells, improper number of cyst divisions, mitotic synchrony defects). However, when two copies of the Dsim\bambam.T:Avic\GFP-YFP.Venus transgene are used, the fertility of the rescue females is reduced (compared to one copy rescue) and they become virtually sterile by day 15. They also show accelerated loss of the germline stem cells from the ovaries and often lack them or any germline cells altogether. These effects are alleviated even by a single copy of endogenous wild-type bam. The partial fertility of bamΔ59/bamΔ86;Dsim\bambam.T:Avic\GFP-YFP.Venus xenogenetic rescue flies is also improved by Wolbachia pipientis infection.
Expression of bam4.1.T:Avic\GFP-YFP.Venus restores fertility of the otherwise sterile bamΔ59/bamΔ86 females and bamBG/bamΔ86 males, although under sperm exhaustion conditions the rescue is not complete. Ovaries of the rescue females have wild-type morphology.