E2fi2/E2f07172 trans-heterozygotes are viable and can complete oogenesis. Eggs laid by these females display a variety of dorsoventral polarity defects, including eggshells with fused dorsal appendages (ventralised, 22%), eggshells with fused but slightly expanded dorsal appendages (between dorsalised and ventralised, 39%), and eggshells with fused but widely spread dorsal appendages (strongly dorsalised, 11%). In addition, 8% of the eggs laid by E2fi2/E2f07172 females have greatly degenerated dorsal appendages, which obscure the dorsoventral polarity pattern of these eggshells.
In wild-type animals, exposure to 40Gy of γ rays induces a distinct pattern of apoptosis in the wing disc, focussed on the the wing pouch, but excluding the DV boundary region and prospective vein. In E2fi2 homozygotes, the same irradiation treatment induces less cell death was reduced in the intervein regions but increased cell death at the D/V boundary.
The ovaries of E2fi2/Df(3R)e-BS2 females are smaller than wild-type but have the normal complement of nurse and follicle cells. Occasionally, degenerating early egg chambers (stage 8 and earlier) are seen. The predominant defects in E2fi2/Df(3R)e-BS2 females are a failure of nurse cells to deposit their contents into the oocyte and degenerate and an increased amount of heterochromatic DNA in the nurse cell nuclei. This appears to be caused by continued replication, when normally replication is blocked by a reduction in E2f activity. In E2fi2/Df(3R)e-BS2 mutants defects in nurse cell chromosome morphology are also seen. Although mutant chromosomes go through the polytene and bulbous states, the homologous copies of each of the large chromosomes are frequently separated rather than associated as in wild-type. The fourth chromosome is always a single sphere. Sister chromatids often do not separate after the bulbous stage, becoming more condensed and having a polytene rather than interphase appearance. Individual chromosome arms are visible, and the chromosomes are clustered as if the homologous sister chromatids remain in proximity. In stage 12 E2fi1/Df(3R)e-BS2 egg chambers the nurse cell nuclear envelope does not break down as normal. In homozygous E2fi2 egg chambers, unlike wild-type (where nurse cells undergo apoptosis during stages 12 to 13 and have degenerated by stage 14), degeneration of nurse cells is abnormal and occurs late if at all. E2fi2/Df(3R)e-BS2 mutant mothers lay few eggs. In the rare cases in which mature eggs are laid most are unfertilized, apparently due to defects in chorion structure. The few fertilized embryos arrest in early division cycles. In addition, the morphology of the polar bodies are affected. In embryos collected from these mothers some have normal polar body rosettes whereas others show aberrant morphology. Only a few eggs show some nuclear divisions, but with aberrant chromosome condensation.
Hemizygotes are fully viable and have slightly rough eyes. Hemizygous females have reduced fertility. E2fi1/E2fi2 flies are fully viable and fertile. One copy of CycE05206 has no effect on the viability of E2fi2/E2f91 flies. E2fi2 flies produce thick and rough eggshells. The size and intensity of foci of BrdU incorporation are increased in the follicle cells of hemizygous egg chambers compared to wild type.