zpg^z-5352/zpg^z-2533 flies are sterile, their testes are rudimentary and have a significant reduction in male germline stem cell number compared with controls. Many zpg^z-5352/zpg^z-2533 mutant testes do not contain GSCs at 1 day post eclosion but most contain germ cells. zpg^z-5352/zpg^z-2533 mutant testes display a large increase in somatic cyst stem cells and early-stage somatic cells, and a significant decrease in late-stage somatic cells compared with controls. There is a significant increase in the number of proliferating somatic cells, but the number of proliferating somatic cyst stem cells is decreased. Cadherin-mediated cell-cell adhesion is unaffected in zpg null testes.

In zpg^z-5352/zpg^z-2533 testes, 2-cell stage spermatogonia display ectopic spectrosomes alongside early fusomes, indicating defective germline differentiation, and germline cyst encapsulation was defective.

Homozygous zpg^z-5352 germline clones are never successfully maintained as germline stem cells.

Homozygous zpg^z-5352 somatic cyst stem cell clones display no defects in stem cell maintenance.

zpg^z-5352/Df(3L)ZN47 males are sterile and have tiny gonads, which contain only small numbers of germ cells. These germ cells usually appear as single or small clusters of cells near the apical tip of the testis, and they appear to have stem cell or gonialblast identity (as they contain spherical spectrin-rich structures). Germ cells in clusters which resemble early spermatogonia have round or slightly tapered spectrin-rich structures, rather than fusomes, which appear larger than the spectrosomes in stem cells. This suggests that the mutant spermatogonia attempt, but are unable to complete, differentiation. The area and number of the hub cells at the apical tip of the testis is often increased compared to wild type. The somatic cyst progenitor and somatic cyst cells appear to be present in the mutant testes, but many of the cyst cells do not appear to enclose germ cells (as only a few germ cells are present) and therefore do not have their characteristic "lacy" appearance. zpg^z-5352/Df(3L)CH12 females are sterile and have tiny gonads. zpg^z-5352/Df(3L)ZN47 females have tiny ovaries. The germaria of newly eclosed females contain only a few germ cells, which appear as single cells at the apical tip of the germarium. These germ cells have spherical spectrosomes, suggesting stem cell or cystoblast identity. Structures resembling egg chambers are occasionally seen further down the ovary (one per 2.9 ovaries) in newly eclosed females and the ovary in this case contains an abnormal number of germ cells that appear to be degenerating. 93% of germaria have germ cells in the stem cell position at the apical tip in 0-3 day old zpg^z-5352/Df(3L)ZN47 females, this decreases to 18% in 21-24 day old females. In some 3 week old females, ovarioles that lack germ cells at the tip have one or a few differentiating egg chambers further down the ovariole. 88% of germaria have germ cells in the stem cell position at the apical tip in 0-3 day old zpg^z-5352/Df(3L)CH12 females, this decreases to 24% in 21-24 day old females. 70% of germaria have germ cells in the stem cell position at the apical tip in 0-3 day old zpg^z-5352/Df(3L)CH20 females, this decreases to 21% in 21-24 day old females.