The dot-like small eye phenotype characteristic for flies expressing egrScer\UAS.cMa under the control of Scer\GAL4GMR.PFa is partially suppressed by combination with Rac1J10, together with Rac2Δ and MtlΔ, all in heterozygous state.
Pupal retina constituting almost entirely of somatic clones (induced specifically in the eye) triple homozygous for Rac2Δ,Rac1J11,MtlΔ do not show any extra cone cells or primary pigment cells, only extra inter-ommatidial cells are observed.
After single cell wounding (by laser ablation), Rac triple mutant embryos (Rac1J10, Rac2Δ, MtlΔ) show severe disruption of actin cortical flow, affecting both actin ring and actin halo formation, resulting in wound overexpansion and an aberrant oval (rather than rounded) wound shape.
The presence of Rac2Δ/+, Rac1J11/+ and MtlΔ/+ mutations fails to suppress the reduction of differentiation seen in eye-antennal disc clones expressing both RhoGEF2RE.Scer\UAS and Ras85DG12V.Scer\UAS under the control of Scer\GAL4tub.PU, and also fails to suppress the developmental delay shown by larvae containing these clones.
Co-expression of Ced-12Scer\UAS.cGa and mbcScer\UAS.cBa via Scer\GAL4Mef2.PR results in prevalent myoblast fusion, muscle attachment, and tendon cell identity phenotypes in embryos. The muscle attachment and tendon cell phenotypes are largely rescued in a Rac1J11/+, Rac2Δ/+ background.
ZirBG00267/+ ; Rac2Δ/+ double heterozygous larvae have a reduced rate of encapsulation (42%) of eggs of the avirulent wasp strain L. boulardi G486 compared to the rate seen in either single heterozygote.
Myoblast fusion is defective in Rac1J11 Rac2Δ double mutant embryos, although some fusion does occur. Binucleate muscle precursors that have undergone a single fusion event between a founder cell and a fusion competent myoblast are seen in the mutant embryos as follows: DA1 (64.2% of segments), DO1 (68.3% of segments), LO1 (26.3% of segments), VT1 (66.7%) of segments.
A mild, though not significant enhancement of the ommatidium-phenotype resulting from the co-expression of Arf51FGD13822 with Dcr-2Scer\UAS.cDa under the control of Scer\GAL4GMR.PF is observed in a Rac1J11, Rac2Δ, MtlΔ heterozygous background.
No rhabdomeric defect is seen at the base of the rhabdomere at eclosion in flies in which the eyes are triply mutant for Rac1J11 Rac2Δ MtlΔ, although there is an axon guidance defect in the optic lobe.
The eye phenotype seen when vavΔ1-207.Scer\UAS.T:Ivir\HA1 is expressed under the control of Scer\GAL4GMR.PU is suppressed in a homozygous Rac2Δ background. The phenotype is not suppressed in a Rac2Δ/+ background.
prtpΔ1/+ ; Rac1J11 Rac2Δ/+ triple heterozygotes show a reduced level of phagocytosis in embryonic hemocytes (neither prtpΔ1/+ single heterozygotes nor Rac1J11 Rac2Δ/+ double heterozygotes show a reduction in phagocytosis compared to wild type).
A Rac1J11 Rac2Δ MtlΔ heterozygous background enhances the patterning defects found in Scer\GAL4GMR.PF>cindrdsRNA.PC.PD.Scer\UAS mutants. The mean interommatidial precursor cell number and the number of cone and/or 1[o] cell errors is increased in these double mutants.
The Scer\GAL4elav-C155/DAAMC.Scer\UAS.P\T gain-of-function phenotype (i.e the appearance of thicker commissures and nerve roots) is not affected by a Rac1J11, Rac2Δ background or a Rac1J10, Rac2Δ, MtlΔ background.
Rac1J11, Rac2Δ, MtlΔ triple mutant clones in the eye result in a low frequency (approximately 5%) of planar polarity defects (such as achiral or misrotated ommatidia). Cdc425, Rac1J11, Rac2Δ, MtlΔ quadruple mutant clones in the eye result in a higher frequency of (14.2%) of planar polarity defects.
The salivary gland defects seen in Rac1J11 embryos are enhanced in Rac1J11 Rac2Δ mutants; more cells remain at the ventral surface of the embryo and the gland fails to migrate posteriorly. In addition, the lumen of the salivary gland is disrupted, with breaks in the lumen being seen during posterior migration of the gland, and cyst-like lumena being seen in the mature gland.
shi2 Rac1J11 Rac2Δ MtlΔ heterozygous embryos form normal salivary glands at the permissive temperature of 25[o]C. However, at the restrictive temperature of 30[o]C, posterior migration of the salivary gland is disrupted.
The Rac2Δ mutation fails to modify the cv-cM62 phenotype in the Malpighian tubules. Dorsal closure defects occur in 82% of Rac1J11, Rac2Δ double mutant embryos. If these mutants also carry the cv-cM62 mutation , 37% of these embryos are rescued. In cv-cM62, Rac1J11, Rac2Δ triple mutants, the posterior spiracle phenotype is enhanced compared to cv-cM62 mutants. Posterior spiracle phenotypes are seen in Rac1J11, Rac2Δ embryos, but with low penetrance.
In Rac1J11; Rac2Δ double homozygous embryos, rearrangement of tubule cells to produce elongated, 2 cell wide tubules is partially disrupted and tubule migration is defective. The anterior tubules follow an erratic path, doubling back on themselves to form loops and knots.
One hour after laser-induced wounding, approximately half the number of hemocytes are recruited to the wound in embryos triply mutant for Rac1J11, Rac2Δ and MtlΔ compared to wild type embryos. Hemocytes that are recruited in the triple mutant embryos have significantly reduced lamellar protrusions.
Contacts between the invaginated mesoderm and the ectoderm fail to be established properly in embryos derived from females with reduced Rac2 and Rac1 function. Contacts between the invaginated mesoderm and the ectoderm fail to be established properly in embryos derived from females with reduced Mtl, Rac2 and Rac1 function.
Germ line clones of the Rac1J11 Rac2Δ MtlΔ triple mutant fail to produce embryos. Zygotic Rac1J11 Rac2Δ MtlΔ triple mutants, that have wild-type maternal contribution of Rac1, survive beyond early dorsal closure, but still show 100% embryonic lethality. These embryos achieve dorsal closure, but show puckering along the dorsal side. The dorsal hole becomes a long slit-like shape as it closes in the triple mutants, while the hole has an oval shape in wild-type embryos. Although amnioserosa cells are significantly larger in the mutant than in wild type, these cells are able to contract at a similar rate to wild type. The leading edge of zygotic Rac1J11 Rac2Δ MtlΔ triple mutants is disorganized and, unlike in wild-type embryos, is not taut. Many of the triple mutant leading edge cells are polygonal in shape, instead of being dorsally-ventrally elongated, like in wild type. Some of the cells in the mutant edge assemble the actin cable and actin projections, while other cells fail to do so. Leaky expression of hepCA.Scer\UAS, with no GAL4 driver, partially rescues the lethality and dorsal puckering phenotype of Rac1J11 Rac2Δ MtlΔ triple mutants. Rac1J10 Rac2Δ MtlΔ triple mutant germ line clone embryos exhibit failure in germband retraction, head involution and dorsal closure. Not all of these phenotypes are fully penetrant; embryos with the least severe phenotype show only failure in dorsal closure. The epithelial cells of these embryos lack both actin cables and actin protrusions at the leading edges. The leading edge of zygotic Rac1J10 Rac2Δ MtlΔ triple mutants is somewhat disordered. Some of the cells in the mutant edge assemble the actin cable and actin projections, while other cells fail to do so. Cells without protrusions halt the "zipper" that closes the dorsal hole. However, the mutant exhibits a compensatory mechanism in which new zippering fronts emerge after the actin deficient stretches to complete closure.
Rac1J10 Rac2Δ MtlΔ triple mutant embryos (lacking both maternal and zygotic function of the Rac1, Rac2 and Mtl genes) are able to almost completely dominantly suppress the stidsRNA.Sym.Scer\UAS (under the regulation of Scer\GAL4ey.PB) phenotype, reverting the eye to wild-type size and appearance. Rac1J10 Rac2Δ MtlΔ triple mutant embryos (lacking both maternal and zygotic function of the Rac1, Rac2 and Mtl genes) are able to dominantly suppress the RacGAP50CdsRNA.Scer\UAS (under the regulation of Scer\GAL4ey.PB) eye phenotype.
Rac1J11, Rac2Δ or mutant embryos exhibit arrested ganglionic branches (GBs), and GBs turning prematurely away from the midline. robo4 partially suppresses the ganglionic branch phenotype seen in Rac1J11, Rac2Δ embryos.
Homozygous Rac1J10 Rac2Δ embryos derived from homozygous Rac1J10 Rac2Δ female germline clones show mild defects in macrophage migration as macrophages do not disperse into the ventral posterior trunk region by stage 14 or 15. By late embryogenesis, macrophages have dispersed throughout the entire ventral trunk in these embryos. Sibling embryos that are derived from homozygous Rac1J10 Rac2Δ female germline clones but are zygotically heterozygous for Rac1J10 Rac2Δ (having received a paternal wild-type copy of Rac1 and Rac2) show a normal distribution of macrophages.
Homozygous Rac1J10 Rac2Δ MtlΔ embryos derived from homozygous Rac1J10 Rac2Δ MtlΔ female germline clones show the same macrophage migration defects as homozygous Rac1J10 Rac2Δ embryos derived from homozygous Rac1J10 Rac2Δ female germline clones.
In a subset of the epidermis of stage 15 Rac1J11, Rac2Δ double homozygous embryos the distinction between apical and basolateral domains is compromised. At stage 16 the columnar epithelial cells are shorter than wild-type and parts of the epidermis become multilayered. Rac1J11, Rac2Δ double homozygous embryos exhibit a variety of tracheal defects: The mildest phenotype is a misrouting of the dorsal branches toward the anteroposterior direction, whereas more severely effected embryos also exhibit truncations of the dorsal trunk.
The combination of heterozygous sli2 and Rac2Δ leads to longitudinal axon ectopic midline crossing defects. An average of 1.4 defects are seen per animal, and an average of 13% of segments have defects.
Rac1J10 Rac2Δ MtlΔ triple mutant embryos (lacking both maternal and zygotic function of the Rac1, Rac2 and Mtl genes) fail to complete dorsal closure. There is little or no actin accumulation at the leading epidermal edge and both lamellipodia and filopodia are lacking. The underlying amnioserosa cells appear normal. Little or no myoblast fusion occurs in these embryos. Severe axon growth defects are seen; in the CNS, Fas2-positive axons rarely extend from one segment into the next and very few sensory axons from the PNS reach the CNS. Specification of neuronal and glial cell fate and dendritic growth and morphology appears relatively normal. Rac1J10 Rac2Δ double mutant embryos (lacking both maternal and zygotic function of the Rac1 and Rac2 genes) show dorsal closure defects. Little or no myoblast fusion occurs in these embryos. Rac2Δ MtlΔ double mutant embryos (lacking both maternal and zygotic function of the Rac2 and Mtl genes) successfully complete dorsal closure. A few isolated myoblasts fail to fuse in these embryos. Rac1J11 Rac2Δ MtlΔ triple mutant clones in the wing and eye do not show planar cell polarity defects. Rac2Δ enhances the frequency of midline guidance defects in MtlΔ mutant embryos to 42%. Less than 2% of Rac1J10 Rac2Δ mutant embryos show midline guidance defects (Fas2-positive longitudinal axons crossing the midline). Mosaic flies in which the eye is doubly mutant for Rac1J10 and Rac2Δ show mild defects in the projection pattern of photoreceptor cell axons. Mosaic flies in which the eye is doubly mutant for Rac1J11 and Rac2Δ show mild defects in the projection pattern of photoreceptor cell axons. Mosaic flies in which the eye is doubly mutant for MtlΔ and Rac2Δ show mild defects in the projection pattern of photoreceptor cell axons. Mosaic flies in which the eye is triply mutant for MtlΔ, Rac1J10 and Rac2Δ show severe defects in the projection pattern of photoreceptor cell axons, showing a medulla bypass phenotype. The projection defects in the triple mutant eyes can be rescued by Rac1GMR.PNe or MtlGMR.PN. Mosaic flies in which the eye is triply mutant for MtlΔ, Rac1J11 and Rac2Δ show severe defects in the projection pattern of photoreceptor cell axons, showing a medulla bypass phenotype. Specification of photoreceptor cell fate appears to be normal.
55% of Rac1J11 Rac2Δ double mutant neuroblast clones show defective guidance. 55% of Rac1J11 Rac2Δ MtlΔ single-cell γ neuron clones in the mushroom body show axon-stalling defects, mostly at the peduncle. There is a significant reduction in total dendritic length and number of dendritic segments per neuron compared to wild type. Mushroom body axon growth defects in single-cell Rac1J11 Rac2Δ MtlΔ γ neuron clones are largely rescued by expression of Rac1Scer\UAS.T:Hsap\MYC or Rac1Y40C.Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4OK107. Mushroom body axon growth defects in single-cell Rac1J11 Rac2Δ MtlΔ γ neuron clones are not rescued by expression of Rac1F37A.Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4OK107. 81% of axons in Rac1J11 Rac2Δ mushroom body clones show mutant phenotypes, predominantly guidance (55%) and branching (24%) defects. Expression of Rac1Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4OK107 markedly rescues these defects. Expression of Rac1Y40C.Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4OK107 does not reduce the total percentage of axonal defects in Rac1J11 Rac2Δ mushroom body clones, but results in a marked shift in the distribution of defects, with most showing branching (45%) rather than guidance (31%) defects. Analysis of Rac1J11 Rac2Δ mushroom body clones indicates cell non-autonomous effects in axon guidance and branching caused by defective "Rac" activity.
Expression of Rac1Scer\UAS.cLa under the control of Scer\GAL4sns.PK strongly rescues the myoblast fusion defects of Rac1J11 Rac2Δ double mutant embryos, resulting in a near normal somatic muscle pattern. In contrast, expression of Rac1Scer\UAS.cLa under the control of Scer\GAL4kirre-rP298 rescues the myoblast fusion defects of Rac1J11 Rac2Δ double mutant embryos much less efficiently.