Mosaic border cell/polar cell clusters containing ptcS2 clones present increased polar cell and total cell numbers, as compared to controls. ptcS2 follicle cell clones also lead to abnormal stalks, with increased cell numbers, as compared to controls.
ptcS2 homozygous clones show an excess of polar/stalk cells while still producing main body cells, as compared to controls; clones in the egg chamber poles show a severe decrease in apoptosis (i.e. cDcp1-positive cells), as compared to control clones; clones in the germarium, however, are of comparable sizes to control clones.
Homozygous clones induced using the ey-FLP/FRT system result in overgrowth of the eye. The overgrown tissue is cos[+], suggesting that the clone acts non-autonomously. Homozygous clones are not recovered in the adult eye. Overgrowth is also seen in the head cuticle and the antennae.
ptchdl animals transheterozygous for ptcS2 are viable with lowly penetrant headcase defects and they do not display any locomotor defects in adulthood.
Homozygous follicle stem cell clones show duplication and enhanced longevity compared to controls.
Homozygous clones in the eye disc result in tissue invagination.
Ectopic photoreceptor cell clusters differentiate in and around ptcS2 homozygous clones in the eye disc.
When mutant clones are made in the legs of female adults, slightly thickened bristles are seen, indicating a weak transformation to male.
ptcS2/ptctuf-1 flies have enlarged eyes and enlarged head vertex (ocellar triangle, fronto-orbital plate and frons). Other head defects in these flies vary from outgrowths of head cuticle plus large numbers of missing, misplaced or ectopic head bristles to one or 2 misplaced or missing head bristles. ptc559.1/ptcS2 flies have normal sized eyes and head vertex and a low incidence of ectopic or misplaced head bristles. ptcS2 somatic clones in the head vertex region (ocellar triangle, fronto-orbital plate and frons) cause formation of ectopic ocelli and bristles in lateral regions of the head vertex. These ectopic ocelli are often accompanied by an outgrowth of the adjacent eye tissue. Very rarely (<1%), where clones fill the entire head vertex, there is a severe reduction in head size due to almost complete lack of frons and orbital cuticle.
ptchdl in combination with ptcS2 does not lead to any head capsule defects.
Homozygous cells in the anterior of mosaic wing imaginal discs minimise contact with neighbouring ptc+ cells, resulting in round clones with smooth borders.
Larvae show no proventricular defects. Mutants transheterozygous for ptctuf-1 and ptcS2 show normal separation of wing veins L3 and L4, but display dramatic shape changes and abnormalities in the anterior margin. Mirror duplications of the proximal half of the anterior wing are seen.
Short stalks of wild type ovarioles are replaced by large masses of stalk cells in mutant ovarioles. The extra cells are due to overproliferation - an effect that is cell autonomous. Loss of ptc activity leads to a doubling of somatic stem cell number. The two stem cells can remain adjacent or migrate away from each other.
Ovarioles containing homozygous mutant stem cell derivatives (in mosaic females) accumulate an excess of follicle cells, especially between egg chambers. Many egg chambers contain ectopic polar cells. Follicle cells proliferate beyond stage 6 (mitosis occurs up to stage 10) in mutant ovarioles, in contrast to wild type. In mosaic ovarioles, only mutant follicle cells are found to proliferate beyond stage 6; this phenotype is cell autonomous. Many nuclei of mutant follicle cells are smaller than those of surrounding wild-type follicle cells in stage 10 egg chambers. 1 or 2 groups of ectopic border cells are often found in stage 9-10 mutant ovarioles. These ectopic border cells are often found overlying nurse cells in stage 10 egg chambers, indicating defective migration. The oocyte is not at the posterior of the egg chamber in 32% of cases. Mis-positioned oocytes are seen as early as region 3 of the germarium. Mis-placed oocytes are only found in mosaic oocytes which contain mutant follicle cells, although there is no correlation between oocyte position and the location of the mutant cell. Defects in anterior-posterior polarity are seen within the oocyte in stage 8-10 egg chambers even when the oocyte occupies its normal posterior position; in 25% of cases the oocyte nucleus has failed to migrate from the posterior to the anterior cortex. This phenotype does not correlate with the germline ptc genotype in mosaic egg chambers. Most of the egg chambers with altered oocyte polarity (abnormal position of the nucleus) are composed entirely of homozygous mutant somatic cells. Mosaic egg chambers only show polarity defects within the oocyte if the homozygous mutant clone covers the entire posterior of the egg chamber. Egg chamber polarity and oocyte polarity in mosaics can only be disrupted if somatic cells lose ptc+ activity at least 4 days prior to forming part of a stage 8 egg chamber.
Anterior-dorsal ptcS2 clone in dppd-blk eye disc causes ectopic differentiation ahead of the morphogenetic furrow, this wave of ectopic differentiation propogates into neighbouring ptc+ tissue. A ventral margin clone in dppd-blk eye disc causes ectopic differentiation that propogates into ventral ptc+ tissue. Clone spanning a large portion of ventral epithelium and ventral posterior margin rescues ventral differentiation to a relatively normal pattern.
Mosaic clones doubly mutant with knKN2, knKN3 or knKN4 reorganise the wing when induced in the anterior compartment. Clones induced near the anterior margin induce a complete duplication of the anterior wing blade. Phenotype is very similar to clones mutant for ptcS2 alone that affect global reorganisation. The kn mutant affects local alteration in wing patterning associated with ptc inactivation.
Ovarioles containing ptcS2 clones exhibit ptc- cells that are mostly present in giant 'stalks', which are often mispositioned with respect to egg chambers. These defects mimic the effect of ectopic hh expression.
Adult clones in the eye show abnormal ommatidial structure and orientation. Clones cause considerable overgrowth and deformation of the eye. Ectopic equators can be induced in the wild type tissue near the ptc- clones. Clones located ahead of the morphogenetic furrow are associated with fields of precociously differentiating ommatidia. Differentiation is graded with the more mature ommatidium found near the centre of the clone. The axes of the five cell ommatidial clusters are not necessarily aligned with the A/P and D/V axes of the disc.
Homozygous ptcS2 clones cause ectopic expression of dpp and wg in wing and leg discs and similar reorganisations of anterior wing, notum and leg pattern in the adult.
Ommatidia within a clone are invariably mutant, ommatidia may have extra or less photoreceptor cells, appear to be of either chiral form and in a random orientation. Ommatidia in a region posterior to a clone are of the inappropriate chiral form but they are still mirror reflection either side of the equator. This presumable reflects the backward flow of the ectopic wave before it meets the anteriorly advancing endogenous wave. Ommatidia anterior to the clones have the correct chirality and orientation as the morphogenetic ectopic wave is moving in the correct posterior to anterior direction. It is unclear of ommatidial chirality is perturbed in regions where the morphogenetic wave flows perpendicular to the normal direction.
There is a significant shortfall in ptc mutant clones recovered between the anterior wing margin and vein 2 in animals mosaic for homozygous clones of ptcS2. Clones that do form in the anterior compartment never form part of a vein and wild-type cells bordering these clones often form ectopic vein.
Keilin's organ ptc mutant embryos have Keilin's organs, but these often have four or more sensory hairs rather than the normal three. ptcS2/ptcG12 and ptcS2/ptc9 embryos grew in in vivo culture, producing implants containing larval gut, Malpighian tubule, fat body, salivary gland, brain and imaginal discs. The discs tended to grow as a mass of merged sheet of material. Metamorphosed implants produced adult cuticular structures derived from the eye-antenna, leg and wing discs.