shg1 somatic clones in an otherwise wild-type background are excluded from the neuroepithelium, form rosettes beneath the outer optic anlage and undergo apoptosis in late third instar larvae. shg1 mutant cells do not show signs of differentiation or neurogenesis.
In contrast to wild-type, shg1 mutant germline stem cell and somatic stem cell clones are not maintained in the testis. However, progeny of shg1 mutant somatic stem cells do contribute to the apical hub at a frequency similar to progeny from wild-type somatic stem cells.
Clones mutant for shg1 in the imaginal wing disc have a roundish smooth shape and their cells are apically constricted.
Homozygous mutant embryos lack a head and ventral epidermis, which results in a lack of head and ventral cuticle. When homozygous somatic clones are made in nurse cells or border cells, the border cells are prevented from penetrating between nurse cells. The oocyte is also often mislocalized in clones, both germ-line clones and somatic clones in the follicle cells. When somatic clones are made in the follicle cells, mutant cells sort away from wild-type generating a smooth boundary at the interface.
Border cells in ovaries where the nurse cells are somatic clones of shg1, fail to migrate and do not form long (20-40 μm) or intermediate length (10-20 μm) cellular extensions. This is also the case for border cells that are part of a shg1 somatic clone, whether or not the adjacent nurse cells are also shg1 mutant.
When homozygous somatic clones are made in the thoracic epithelium, mutant cells have a smaller apical surface than their wild-type neighbours. Apical-basal polarity is defective in these cells.
Homozygous female germ line clones give rise to egg chambers with misplaced oocytes in 73% of cases. Region 2 cysts never stretch across the whole width of the germarium, thereby preventing the positioning of the oocyte in the centre of the flattened disk. The oocyte occupies random positions in these cysts. The misplaced oocytes are properly determined and have a normal karyosome. The oocyte is misplaced in 23% of mosaic cysts which contain a homozygous clone that includes the follicle cells at the posterior of the cyst. The misplaced oocyte lies adjacent to the wild-type follicle cells in these mosaic cysts. The oocyte is correctly localised in mosaic cysts where the homozygous clone includes only lateral or anterior follicle cells.
Eggs chambers of homozygous female germline clones show a number of defects, including mispositioning of the oocyte and disruptions of the actin cytoskeleton (such as floating ring canals). Nurse cells are an irregular size and shape and can be multinucleate. Nurse cell dumping is inhibited.
shg1/shg2 transheterozygotes exhibit lack of head skeleton, loss of ventral cuticle and the appearance of holes in the lateral cuticle. Heterozygous embryos are completely normal.
embryonic lethal. Embryonic cuticle has many small holes with necrotic rims. Head grossly distorted. Weak alleles show head defects and irregular flaws in segmentation pattern.