interommatidial bristle & eye disc & pupa
The proportion of hemisegments with abnormal number of neurons in the asymmetrically dividing RP2 neural lineage is significantly increased in cno2/+;Mer4/+ double heterozygous embryos compared to either of the single heterozygotes or wild type.
Somatic clones homozygous for Mer4 and exe1 in the antenna or in the dorsal thorax are massively overgrown. In the mid-pupal retina, these clones contain a large excess of inter-ommatidial cells. In the late third instar eye disc, cells in these clones show increased levels of mitosis after (posterior to) the second mitotic wave. Later, at around 25 hours APF, the widespread apotosis seen throughout the developing retina in wild-type and heterozygous cells, is largely suppressed in these clones.
Neither the adult eye phenotype seen in hpoScer\UAS.cUa; Scer\GAL4GMR.PF animals, nor the loss of interommmatidial cells and increased cell death seen in mid-pupal retinas of these animals is suppressed in exBQ Mer4 double homozygous clones.
Mer4; ex697 double mutant eye-antennal imaginal discs have severely reduced eye primordia with a substantial reduction in or total absence of photoreceptors. In these mutants, photoreceptor development and overall eye field size are severely reduced. The antennal portion is normal or slightly larger than normal and in some cases is duplicated. Apoptosis does not seem to be affected.
Mer4; ex697 somatic clones in contact with the posterior or lateral margin of the eye fail to produce photoreceptors. Those somatic clones located in the middle of the eye field can produce photoreceptors.
Mer4; exe1 somatic clones in contact with the posterior or lateral margin of the eye fail to produce photoreceptors. Those somatic clones located in the middle of the eye field can produce photoreceptors.
Both vein and intervein cells can differentiate in Mer4; exe1 double mutant clones in the wing. Clones that intersect the position of the posterior crossvein disrupt its development. Clones in the position of the anterior crossvein develop normally. Within the mutant intervein and vein clones, apparent defects in proliferation control are seen; in the proximal region of the wing, clonal vein tissue forms a raised protrusion. In other regions of the wing, bulges in the veins are also seen, although more frequently vein clones are merely broadened when compared with the surrounding vein. In the intervein regions, the clonal tissue appears to bulge and crinkle within the confines of the normal tissue, suggesting overproliferation. Cells within the intervein clones appear to differentiate as intervein cells, however, the cuticle deposited at the base of each wing hair within the clone appears to be thickened, and is distinct from cuticle produced by either the surrounding heterozygous intervein or vein cells. Mer4; exe1 double mutant clones in the eye appear to disrupt the progression of the morphogenetic furrow, being seen either as small scars with associated clusters of bristles or as elongated scars and associated indentations running from within the eye field towards the anterior margin. These clones do not differentiate ommatidia. The clones are often associated with overproliferated head cuticle.
Scer\GAL4T80 expression of Hsap\NF2Scer\UAS.Iso1.T:Zzzz\FLAG partially suppresses lethality (approximately 60% rescue) in Mer4/y male flies; increased genetic dosage (two copies of Hsap\NF2Scer\UAS.Iso1.T:Zzzz\FLAG) further suppresses lethality (72% rescue). Scer\GAL4T80 expression of Hsap\NF2Scer\UAS.Iso2.T:Zzzz\FLAG provides poor rescue of lethality (8%) in Mer4/y male flies; increased genetic dosage completely fails to suppress lethality (0%). Scer\GAL4T80 expression of Hsap\NF2L64P.Scer\UAS.T:Zzzz\FLAG (one or two copies) partially suppresses lethality (approximately 70% rescue) in Mer4/y male flies. Scer\GAL4T80 expression of Hsap\NF2K413E.Scer\UAS.T:Zzzz\FLAG (one copy) partially suppresses lethality (approximately 36% rescue) in Mer4/y male flies; two copies further suppresses lethality (62%). Scer\GAL4T80 expression of Hsap\NF2Δ2-3.Scer\UAS.T:Zzzz\FLAG or Hsap\NF21-301.Scer\UAS.T:Zzzz\FLAG or Hsap\NF2351-595.Scer\UAS.T:Zzzz\FLAG or Hsap\NF21-356.Scer\UAS.T:Zzzz\FLAG or Hsap\NF2300-595.Scer\UAS.T:Zzzz\FLAG (one or two copies) does not suppress lethality (0-2% rescue) in Mer4/y male flies. Scer\GAL4T80 expression of two copies of Hsap\NF2R466X.Scer\UAS.T:Zzzz\FLAG partially suppresses lethality (approximately 11% rescue) in Mer4/y male flies; one copy completely fails to suppress lethality (0%).