At stage 11 expression of crbUAS.cWa under the control of Scer\GAL4da.G32 results in fewer neuroblasts when compared to control embryos.
Salivary gland primordia expressing crbScer\UAS.cWa under the control of Scer\GAL4fkh.PH still form an invagination pit during stage 11 of embryogenesis, although frequently exhibiting a slight increase in width, still form an apparently normal supra-cellular myosin cable, and do not present significant changes in circularity, but their cells exhibit an increased apical cell surface before invagination, which further expands instead of constricting during invagination, as compared to controls; the region to the anterior of the presumptive invagination site fails to cluster the primordium cells with lower apical surface area, and these cells only form small- and medium-sized apical foci of Rok protein, despite of still forming big foci of myosin, as compared to controls. These crbScer\UAS.cWa-expressing salivary gland primordia do not exhibit significant delays in internalization and migration by stage 14 of embryogenesis, but are occasionally found partially or completely externalized by stages 15 or 16 of oogenesis, as compared to controls.
The expression of crbUAS.cWa under the control of Scer\GAL4ninaE.PTa induces a moderate overgrowth of the photoreceptor cell stalk membrane.
Salivary gland cells overexpressing crbScer\UAS.cWa (under the control of Scer\GAL4fkh.PH) maintain tight contact with their neighbors along the entire lateral domain.
Expression of crbScer\UAS.cWa under the control of Scer\GAL4tub.PU in follicle cell clones results in a loss of polarity, as seen by the spheroidal shape of the cells. In addition, the cuboid-to-squamous transition of the stretched follicle cells that normally occurs at stage 9 of oogenesis is blocked if they are expressing crbScer\UAS.cWa under the control of Scer\GAL4tub.PU.
Expression of crbScer\UAS.cWa under the control of Scer\GAL4btl.PS results in an increase in the diameter of the dorsal trunk lumen compared to wild type.
Expression of crbScer\UAS.cWa under the control of Scer\GAL4ey.PH leads to a very strong gain-of-function phenotype characterised by a complete loss of the head.
Scer\GAL4ninaE.PTa-mediated expression of crbScer\UAS.cWa results in a huge expansion of the stalk membrane. Otherwise, photoreceptor cell morphogenesis is not affected.
Expression of crbScer\UAS.cWa using Scer\GAL4GMR.PF disrupts the regular array of ommatidial lattices and significantly reduces the number of elav- and B-positive cells. Also, photoreceptor nuclei are positioned randomly within the epithelium rather than being restricted to the apical side (as in wild type).
At 55% Pupal Development (PD), Scer\GAL4hs.PB, crbScer\UAS.cWa flies heat shocked at 35% PD have adherens junctions that usually terminate prematurely and are randomly distributed over the ommatidium; flies heat shocked at 40% PD have incomplete adherens junctions; the adherens junctions defects in flies heat shocked at 45% PD are mainly close to the retinal floor.
At 55% Pupal Development (PD), Scer\GAL4hs.PB, crbScer\UAS.cWa flies heat shocked at 35% PD have irregular and mislocalized rhabdomere precursors, and the number and position of adherens junctions per ommatidium are abnormal; flies heat-shocked at 40% PD have expanded rhabdomere domains; flies heat-shocked at 40% are have nearly wild type rhabdomere organization.
The end cells of the amnioserosa are more apically constricted than the middle cells of the amnioserosa in stage 13 embryos expressing crbScer\UAS.cWa under the control of Scer\GAL4332.3.
Expression of crbScer\UAS.cWa driven by Scer\GAL4332.3 results in a failure of 34% of embryos to form cuticle and 44% with dorsal holes. In stage 13 embryos the end cells of the amnioserosa are apically constricted relative to the middle cells. Morphogenesis appears to be induced prematurely in these cells as they look similar to the end cells of stage 14 wild-type embryos. Stage 14 embryos with crbScer\UAS.cWa driven by Scer\GAL4332.3 show a dumbbell-shaped amnioserosa. In stage 14 embryos with crbScer\UAS.cWa driven by Scer\GAL4332.3 the epidermis fails to close up around the amnioserosa, leaving a large dorsal hole that exposes the gut and dorsal vessel. The leading edge cytoskeleton is disrupted and that epidermal cells do not elongate as in wild-types. Overexpression of crbScer\UAS.cWa driven by Scer\GAL4c381 does not cause failure of cuticle formation. However, these embryos do fail to complete dorsal closure and have a large dorsal hole in the cuticle extending from the middle of the dorsal surface to the rear of the embryo. Stage 14 embryos that overexpress crbScer\UAS.cWa driven by Scer\GAL4c381 show little elongation of the epidermal cells.
Expression driven in the third instar eye disc causes loss of cell polarity and pupal lethality, with escapers showing an eye loss phenotype.
Expression of crbScer\UAS.cWa under the control of Scer\GAL4fkh.PH results in an enlarged salivary gland lumen in stage 15 embryos. In stage 16 embryos, the salivary gland lumen is dramatically enlarged and the organisation of the lumen also appears disrupted.
When expression is driven by Scer\GAL4ninaE.PHS photoreceptor cells show a dose-dependent increase in the size of the stalk membrane. The extra membrane forms either a spongy convoluted mass associated with the normal stalk membrane or a large flat membrane expanding the inter-rhabdomere space.
Over expression of crbScer\UAS.cWa when driven by Scer\GAL4da.G32 produces embryos with an epidermis that develops as a multilayered tissue (unlike the single layered epithelium seen in wild-type embryos).
Overexpression of crb results in an expansion of the apical membrane domain accompanied by a reduction of the basolateral membrane domain. The amnioserosa cells lack apical zonula adherens junctions (ZA), spot adherens junctions (SAJ) are also abnormal.
When crbScer\UAS.cWa is expressed from a Scer\GAL4 activator line expressed in a broad stripe of cells in each segment, major parts of the cuticle of crb2 mutant embryos are restored, including the denticle belts. When low levels of crbScer\UAS.cWa are expressed e.g under the influence of Scer\GAL4ptc-559.1 no effects on development are detectable. At moderate levels of expression denticle belts are reduced in size, fail to differentiate properly and exhibit irregular spacing. Dorsal holes result from overexpression in the amnioserosa. At high levels of expression the denticle belts are reduced to tiny, rudimentary structures, in an irregular cuticle organization. Epidermal cells are rounded and exhibit no obvious polarity, and occasionally lie of top of each other. Cell shape changes are particularly evident in the amnioserosa, which fails to invaginate. Overexpression in the hindgut and salivary glands has only minor effects. Ectopic deposition of cuticle occurs in areas of the cell surface that in the wild type would form contacts with cells or extracellular matrix. Cuticle is frequently deposited in deep clefts between adjacent cells. The development of junctions at the remaining contact sites is severely impaired and zonulae adherens and septate junctions are missing. Muscle attachments are affected. The dominant phenotype of crbScer\UAS.cWa is reduced in severity in a background hemizygous for crb+.