Complementation tests show that RanBPM^Δ is lethal in trans with Df(2R)12 and RanBPM^f06647, is semi-lethal with RanBPM^CB-6232-3, and is temperature-sensitive lethal with RanBPM^ΔN.

RanBPM^Δ homozygous mutants exhibit an increase in cell size and terminal filament misalignment.

RanBPM^Δ homozygous mutants expressing RanBPM^S.Scer\UAS under the control of Scer\GAL4^arm.PS exhibit an increase in cell size and terminal filament misalignment, although niche organization is less disrupted than in RanBPM^Δ homozygous mutants not expressing RanBPM^S.Scer\UAS. There is also a significant decrease in the number of cap cells in this genotype, possibly as a result of higher than normal expression of the short RanBPM isoform in the germline stem cell niche. An approximate 30% increase in the mean number of germline stem cells per cap cell in mutant females expressing RanBPM^S.Scer\UAS under the control of Scer\GAL4^arm.PS compared to heterozygous controls. An increase of approximately 30% is observed in cap cell surface area in RanBPM^Δ/RanBPM^Δ ; Scer\GAL4^arm.PS > RanBPM^S.Scer\UAS mutants.

Homozygous RanBPM^Δ mutant terminal cells cells in mosaic niches are larger than wild-type, while both mutant and wild-type cells in mosaic terminal filaments are disorganised. The number of germline stem cells per niche is significantly higher in mosaics compared to non-mosaic controls. This is not caused by a decrease in the size of germline stem cells attached to mutant cap cells, or to an increase in cap cell number, as the number of cap cells in non-mosaic niches is not significantly different from mosaic niches. The mean surface area of homozygous RanBPM^Δ mutant cap cells is increased by 30% relative to controls.

Homozygous RanBPM^Δ mutants do not exhibit a difference in germline stem cell division or any obvious defects in the development of egg chambers. Within mosaic niches, RanBPM^Δ mutant cap cells are attached to twice as many spectrosomes as normal, whereas the wild-type cap cells in the same niches are attached to normal numbers of spectrosomes. Individual mutant cap cells in mosaic niches are observed to contact as many as three spectrosomes, allowing the attachment of up to five spectrosomes to the mosaic cap cell cluster. The 2.2-fold increase in the number of germline stem cells attached to RanBPM^Δ cap cells is greater than the 30% increase in mutant cap cell surface area, indicating a relative increase in the adhesive properties of RanBPM^Δ cap cells compared to wild-type cap cells.

Loss of RanBPM from follicle cells in RanBPM^Δ genetic mosaics can disrupt epithelial organization, causing the single-layered epithelium to become multilayered, which is sometimes associated with fusion of adjacent egg chambers. This phenotype is incompletely penetrant and preferentially affects follicle cells at the anterior and posterior poles of an egg chamber. Loss of RanBPM also causes defects in the morphogenesis of dorsal appendages, the prominent extended chorion structures at the anterior dorsal surface of the eggshell. Dorsal appendages surrounded by RanBPM^Δ mutant cells are much shorter and paddle-like compared to wild-type.