sav3 homozygous mutant embryos display a significant increase in the frequency of hemisegments with abnormal number of neurons in the asymmetrically dividing RP2 neural lineage.
sav3 homozygous embryos from mothers whose germline consisted entirely of sav3 mutant cells (generated by the Ovo[D] germline clone method, which thus are both zygotically and maternally mutant for sav3, display defects in the asymmetric neuroblast (NB) division: disturbed asymmetric localization of polarity and cell-fate determinants as well as high frequency of mitotic spindle orientation defects.
Cells in homozygous clones in the wing disc accumulate F-actin near the apical surface.
Homozygous clones in the eye show progressive degeneration of photoreceptor cells. Autophagic vesicles with partially degraded content accumulate in the mutant photoreceptor cells compared to wild-type cells.
sav3 mutant adult Malpighian tubule clones are significantly enlarged compared to wild-type clones. The mitotic index is increased compared to controls. Mutant clusters typically contain proportionally more renal and nephric stem cells (RNSCs) and renablasts (RBs) compared to control clones. Disrupted cell polarity is observed in mutant cells.
Animals containing mutant eye discs generated using the eyFLP-cell lethal system eclose, and have overgrown eyes.
Mutant eye discs (generated using the eyFLP-cell lethal system) do not show defects in epithelial organisation or neuronal differentiation.
Heterozygous larvae show no significant defects in dendrite morphology of ddaC neurons.
Apoptosis is reduced by up to 3-fold in sav3 clones of wing or eye discs in response to γ-rays compared to wild-type tissue.
sav3 mutant ddaC MARCM clones exhibit dendritic defects, including highly penetrant simplifcation of dendritic trees. In severely affected clones (one fifth), most of the high-order branches are missing, whereas moderately affected clones (approximately 75% of the clones) exhibit a partial loss of their fine branches and major branches.
sav3 heterozygotes do not exhibit an obvious dendritic phenotype.
In sav3 mutants, ddaC dendrites are indistinguishable from wild-type controls at 24-28 hours after egg-laying. By 48-52 hours after egg laying, sav3 mutant dendrites tile the body wall as in wild-type. During the following 24 hours, however, sav3 dendrites disappear from the body wall, implying sav is required for maintenance of the already established tiling of dendrites.
When somatic clones of sav3 homozygous cells are generated throughout the eye disc using Scer\FLP1ey.PN, nearly all of the resulting animals survive to eclosion.
Mosaic flies with eyes containing clones homozygous for sav3 (clones generated using the "eyFLP" system) have large eyes, with an increased representation of mutant tissue over wild-type tissue. Clones made in other parts of the fly including the notum and haltere also display outgrowths. In mutant clones in the adult retina, half of all ommatidia lack one or more photoreceptor cells. However there is increased spacing between adjacent ommatidia - there are many additional interommatidial cells. When mutant clones are made in eye imaginal discs, mutant cells continue to proliferate for 12-24 hours after wild-type cells stop dividing, but are eventually able to exit from the cell cycle and undergo terminal differentiation. When examined by flow cytometry, the cycling cells in the anterior portion of the eye disc have a distribution very similar to that of wild-type cells. The mutant cells are slightly smaller than their wild-type counterparts. Posterior to the morphogenetic furrow, mutant cells have an increased proportion of cells in S2 and G2, indicating that the cells continue to cycle.