General Information
Symbol
Dmel\robo11
Species
D. melanogaster
Name
FlyBase ID
FBal0032588
Feature type
allele
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
roboGA285, robo1, robo1GA285, GA285
Nature of the Allele
Mutations Mapped to the Genome
 
Type
Location
Additional Notes
References
point mutation
Nucleotide change:
C22698188T
Reported nucleotide change:
C1231T
Amino acid change:
Q411term | robo1-PA; Q411term | robo1-PC
Reported amino acid change:
Q411term
Associated Sequence Data
DNA sequence
Protein sequence
 
 
Progenitor genotype
Cytology
Nature of the lesion
Statement
Reference
Nucleotide substitution: C1231T.
Amino acid replacement: Q411term.
Expression Data
Reporter Expression
Additional Information
Statement
Reference
 
Marker for
Reflects expression of
Reporter construct used in assay
Human Disease Model Data
Disease Ontology
Models ( 0 )
Disease
Evidence
References
Interactions ( 0 )
Disease
Interaction
References
Comments ( 0 )
 
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
abdominal basiconical sensillum dbd & embryo & nerve terminal
chordotonal organ & axon | lateral
chordotonal organ & embryo & nerve terminal
Detailed Description
Statement
Reference
The adult sLNv neurons of robo11/robo1BG01092 transheterozygotes do not show significant axon length differences compared to controls.
robo11 homozygous embryonic heart cardioblasts show a rounded morphology, show significant decreases in migration velocity, as well as in filopodial and lamellopodial extensions and activities, as compared to controls; these defects are associated with embryonic heart lumen formation defects, as compared to controls. robo11 heterozygous cardioblasts also show a significant decrease in migration velocity, filopodial activity and lamellopodial activity, as compared to controls.
robo11 homozygous embryos display defects in midline repulsion leading to axons ectopically crossing the ventral nerve cord midline.
robo11/robo11, but not robo11/+, mutant embryos exhibit ventral nerve cord defects, including axon guidance defects, with FasII-positive axons crossing the midline in every segment, and the pCC neuron inappropriately extends across the midline, in contrast to wild type.
Axons from the medial Fas2-positive pathway cross the line in every segment in mutant embryos.
robo1/robo2 embryos exhibit gonad compaction defects and germ cell ensheathment defects.
In robo1 mutants, the medial Fas2-positive axon tracts ectopically cross and recross the midline. The axons expressing Scer\GAL4ap-md544 also collapse along the midline and follow the medial Fas2-tract.
Fas2-positive longitudinal axons show repeated crossing of the midline in robo1/robo8 stage 16 embryos. 99.1% of segments have Fas2-positive axons extending across or along the midline in stage 16-17 homozygous embryos.
Homozygous robo1 mutant embryos display a phenotype where axons repeatedly cross the midline in a circular fashion.
Single cell robo1 leg motoneuron clones induced 48 hr after hatching have the following phenotypes: the posterior dendritic branch crosses the midline at the same site as it does in wild type clones, but there are ectopic branches the that extend toward the midline at more anterior positions within the neuropil; more of the dendritic arborization is found in the medial territory than controls; the mean centre of mass is shifted toward the midline compared to controls; the mean 33rd percentile of arborization is shifted towards the midline. Single cell robo1 leg motoneuron clones induced 96 hr after hatching have the following phenotypes: a shift in the distribution of dendrites toward the midline; the mean centre of mass shifts towards the midline compared to controls; the mean 33rd percentile of arborization shifts towards the midline. There is no evidence for a disruption to the axonal projections of clones to the periphery. In a dorsoventral plane, these clones show a shift of dendrites towards the posterior neuropil and a slight loss in the ventral neuropil.
robo1/robo2 mutants exhibit an ectopic midline innervation phenotype (with 100% penetrance for MN-LL1 and 89% penetrance for MN-DA3).
robo1 mutants exhibit axon guidance defects whereby the commissural axons cross the midline repetitively to give characteristic 'roundabouts'. robo1 heterozygous mutants appear wild-type.
Many of the dorsal abdominal clusters in robo1 mutant animals have branches that exceed the normal level of extension at approximately 21 and 22 hours after egg laying. The maximal dendrite length with respect to the most dorsally positioned neuronal cell body is significantly altered in mutants. Class IV robo1 mutant neurons display dendrite over-elongation and reduced branching. Class IV neurons show less high order branches and form longer dendrite process compared to control embryos. The number of branches of class IV neurons is significantly decreased in robo1 mutants at 22 hours after egg laying. The dorsal elongation and the average branch length are significantly increased. Class I neurons in robo1 mutant embryos do not show any defects in dendrite branch length or number compared to control embryos. robo1 single cell mutant class IV neurons have less high order branches than control clones. The number of quaternary and higher order branches is less than half compared to controls. The average length of all branch orders is unchanged. robo1 single cell mutant clones of either two dorsal class I neurons display normal dendrite morphology.
robo1 embryos show an axon guidance defect of the Apterous neurons with neurons aberrantly crossing the midline. robo1 Apterous neurons exhibit these crossing defects during the initial extension toward the midline and throughout development.
Medial axon bundles abnormally cross and re-cross the midline in homozygous robo1 mutant embryos.
robo1 mutant embryos present a fused commissure phenotype in 100% of neuromeres.
The initial lateral projection and posterior turn of the dMP2 and MP1 pioneer neurons are normal in developing mutant embryos. The axons fasciculate as in wild type and extend their axons posteriorly. When they reach the commissure of the next segment, MP1 crosses the commissure and follows the correct longitudinal pathway. However, most dMP2 axons show an abnormal trajectory at this point, separating from the MP1 axon, tracking the commissural axons and crossing the midline (rather than following a longitudinal pathway as in wild type). The normal anterior projections of the pCC and vMP2 neurons are misdirected contralaterally in mutant embryos.
robo1 embryos show weak salivary gland guidance defects.
Subtle myocardial cell alignment defects are observed in learobo2-8 stage 16 embryos.
In robo1/robo1 embryos there is ectopic midline crossing of most CNS axons, and disorganized and inappropriate serotonergic neuron branching towards the midline. Despite their defects in serotonergic neuronal axon guidance, these neurons retain their normal ability to take up serotonin.
Mutant embryos do not show defects in the position of the vmd1a neuron of the ventral multidendritic neuron cluster in the abdomen; a single vmd1a neuron is seen in each hemisegment.
About 26-40% of heterozygous robo1 stage 16 embryos exhibit axon bundles that cross the midline incorrectly.
Homozygous embryos show sensory axon defects; one or more axons from the lch5 cluster project inappropriately to join the v'ch1 axon or the v' cluster in 10% of hemisegments. In these hemisegments, the remaining lch5 axons project in a normal fashion to the intersegmental nerve. In addition, the axon of one of the lesA and ldaA neurons (usually the lesA neuron) follows the v'ch1 pathway in 23% of hemisegments. Occasionally (3% of hemisegments), v'ch1 or other v' cluster axons grow dorsally before turning back into the segmental nerve or inappropriately joining the intersegmental nerve. No defects are seen in the dorsal trunk, transverse connective or visceral branch.
The terminal branches of the dbd neurons generally cross the midline and often form mirror image bilateral projections. The projections retain their association with the medial Fas2 fascicle. Approximately half of the time the terminal branches of the ch neurons have a branch crossing the midline. The projections retain their association with the intermediate Fas2 fascicle.
In robo1/+ embryos, midline crossovers are seen in the pCC/MP2 pathway axons in 25% of embryos. An average of 1.1 crossovers are seen per embryo.
One or two Fas2-positive axon bundles cross the midline in about 26% of heterozygous embryos.
robo1/+ heterozygous mutant embryos exhibit midline crossing at a frequency of ~4.8%.
43% of heterozygous embryos show abnormal midline crossing of axons.
5% of segments show crossing of the midline by muscles 6/7, 11% show abnormal insertion of muscle 5 and 15% show abnormal insertion of muscles 6/7 in mutant embryos.
Approximately 53% of heterozygous embryos show periodic crossovers of Fas2-positive axons across the midline.
In robo1 mutant embryos all of the innermost fascicles from each side of the midline combine to form a single thick bundle that meanders back and forth along the midline.
The inner Fas2-positive longitudinal bundle crosses the midline and circles around it in the central nervous system of homozygous embryos.
Embryos heterozygous for either robo1 or sli2 show deviation of longitudinal fascicles towards the midline in less than 5% of segments.
The ap-expressing interneurons cross the midline in every segment in homozygous embryos, join up with their contralateral homologues, and often project anteriorly in one discrete longitudinal fascicle. In heterozygous embryos 5% of all ap-expressing axons cross the midline.
Mutant phenotype of lateral chordotonal axons includes: shorter axons or defasciculated axons.
"Fuzzy commisure" phenotype in embryonic central nervous system.
External Data
Interactions
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Enhanced by
Statement
Reference
robo[+]/robo11, sli2 has neuroanatomy defective phenotype, enhanceable by β-Specem6
robo[+]/robo11, sli2 has neuroanatomy defective phenotype, enhanceable by β-SpecG0074
robo[+]/robo11, sli2 has neuroanatomy defective phenotype, enhanceable by β-SpecG0198
chb4, robo11 has neuroanatomy defective phenotype, enhanceable by robo28
robo11, sli[+]/sli1 has neuroanatomy defective | dominant | embryonic stage 16 phenotype, enhanceable by Abl4/Abl[+]
lea[+]/robo28, robo11 has neuroanatomy defective | recessive phenotype, enhanceable by captk01217/capt[+]
NOT Enhanced by
Suppressed by
Statement
Reference
NOT suppressed by
Statement
Reference
Enhancer of
NOT Enhancer of
Statement
Reference
Suppressor of
NOT Suppressor of
Other
Phenotype Manifest In
Enhanced by
Statement
Reference
robo11 has filopodium | embryonic stage phenotype, enhanceable by sli2/sli[+]
robo11 has lamellipodium | embryonic stage phenotype, enhanceable by sli2/sli[+]
robo11 has filopodium | embryonic stage phenotype, enhanceable by fra3/fra[+]
robo11 has lamellipodium | embryonic stage phenotype, enhanceable by fra3/fra[+]
robo11 has filopodium | embryonic stage phenotype, enhanceable by unc-5[+]/unc-58
robo11 has lamellipodium | embryonic stage phenotype, enhanceable by unc-5[+]/unc-58
robo11 has filopodium | embryonic stage phenotype, enhanceable by Dscam1[+]/Dscam11
robo11 has lamellipodium | embryonic stage phenotype, enhanceable by Dscam1[+]/Dscam11
robo11 has cardioblast phenotype, enhanceable by robo28
robo11, sli[+]/sli1 has longitudinal connective | embryonic stage 16 phenotype, enhanceable by Abl4/Abl[+]
robo11 has aCC neuron phenotype, enhanceable by robo25
robo11 has pCC neuron phenotype, enhanceable by robo25
robo11 has longitudinal connective phenotype, enhanceable by sli2/sli[+]
robo11 has longitudinal connective phenotype, enhanceable by sli[+]/sliE-158
NOT Enhanced by
Statement
Reference
robo11 has filopodium | embryonic stage phenotype, non-enhanceable by Dscam105518/Dscam1[+]
robo11 has lamellipodium | embryonic stage phenotype, non-enhanceable by Dscam105518/Dscam1[+]
robo12/robo11 has gonad | embryonic stage phenotype, non-enhanceable by robo24/robo28
robo12/robo11 has gonad | embryonic stage phenotype, non-enhanceable by robo31/robo31
robo11 has dendrite phenotype, non-enhanceable by robo28
chb4, robo11 has embryonic/larval neuron phenotype, non-enhanceable by robo31
robo11 has phenotype, non-enhanceable by Sos[+]/Sose49
Suppressed by
Statement
Reference
robo11 has dMP2 neuron phenotype, suppressible | partially by fra3
NOT suppressed by
Statement
Reference
robo25, robo11 has ventral nerve cord phenotype, non-suppressible by comm1
Enhancer of
Statement
Reference
robo11/robo1[+] is an enhancer of embryonic heart cardioblast phenotype of sli2
robo11/robo1[+] is an enhancer of filopodium | embryonic stage phenotype of sli2
robo11/robo1[+] is an enhancer of embryonic heart cardioblast phenotype of fra3
robo11/robo1[+] is an enhancer of filopodium | embryonic stage phenotype of fra3
robo11/robo1[+] is an enhancer of lamellipodium | embryonic stage phenotype of fra3
robo11/robo1[+] is an enhancer of embryonic heart cardioblast phenotype of unc-58
robo11/robo1[+] is an enhancer of filopodium | embryonic stage phenotype of unc-58
robo11/robo1[+] is an enhancer of filopodium | embryonic stage phenotype of Dscam11
robo11/robo1[+] is an enhancer of filopodium | embryonic stage phenotype of Dscam105518/Dscam11
robo[+], fra3, robo11, fra[+] is an enhancer of midline crossing tract phenotype of Trim946
sli2, robo[+], robo11 is an enhancer of medial longitudinal fascicle | ectopic phenotype of β-Specem6
robo11 is an enhancer of cardioblast phenotype of robo28
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sliF119
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sliGA20
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sliE-158
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sliF81
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sliGA945
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sliGA178
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sli1912
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sli2
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sli550
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sli2990
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sli532
robo[+]/robo11 is an enhancer of ventral nerve cord phenotype of sli3149
robo11 is an enhancer of aCC neuron phenotype of robo25
robo11 is an enhancer of pCC neuron phenotype of robo25
robo[+]/robo11 is an enhancer of longitudinal connective phenotype of sliE-158
robo[+]/robo11 is an enhancer of longitudinal connective phenotype of sli2
NOT Enhancer of
Statement
Reference
robo11/robo1[+] is a non-enhancer of lamellipodium | embryonic stage phenotype of sli2
robo11/robo1[+] is a non-enhancer of lamellipodium | embryonic stage phenotype of unc-58
robo11/robo1[+] is a non-enhancer of filopodium | embryonic stage phenotype of Dscam105518
robo11/robo1[+] is a non-enhancer of lamellipodium | embryonic stage phenotype of Dscam105518
robo11/robo1[+] is a non-enhancer of embryonic heart cardioblast phenotype of Dscam105518
robo12/robo11 is a non-enhancer of gonad | embryonic stage phenotype of robo24/robo28
robo11 is a non-enhancer of phenotype of AblK417N.UAS, Scer\GAL4elav.PLu
Suppressor of
NOT Suppressor of
Other
Statement
Reference
Additional Comments
Genetic Interactions
Statement
Reference
robo11, robo2lea-2 double homozygous embryonic heart cardioblast show similar cell rounding, slow migration and decreased filopodial and lamellopodial activities) to those observed in robo11 single homozygotes; these defects are associated with gaps in the leading edge (and lost adhesions with ipsilateral partners), cell clumping, improper linear alignment of the cardioblasts, and heart lumen formation defects, as compared to controls. The decreased lamellopodial activity, but not the decreased filopodial activity, slow migration, or heart lumen formation, are only partially suppressed by the expression of robo1Scer\UAS.cKa under the control of Scer\GAL4Mef2.247. Only the reduced filopodial and lamellopodial activities observed in robo11 homozygous embryonic heart cardioblasts, but not their reduced migration velocity, nor the associated heart lumen formation defects, are partially suppressed by the expression of fraScer\UAS.cKa under the control of Scer\GAL4Mef2.247. sli2, robo11 and fra3, robo11 double heterozygotes show a more severe decrease in filopodial activity compared to either single heterozygote conditions and a more severe decrease in lamellopodial activity compared to robo11 heterozygotes, but do not show significant changes in migration velocity compared to controls. unc-58, robo11 double heterozygotes show a less severe decrease in migration velocity compared to either single heterozygote conditions, a more severe decrease in filopodial activity compared to either single heterozygote conditions, and a more severe decrease in lamellopodial activity compared to robo11 heterozygotes. Dscam11, robo11 double heterozygotes show a more severe decrease in filopodial activity compared to either single heterozygote conditions, a more severe decrease in lamellopodial activity compared to robo11 heterozygotes, and no migration velocity defects compared to wild-type controls. Dscam105518, robo11 double heterozygotes show a similar decrease in filopodial and lamellopodial activities compared to either single heterozygote conditions, and show no significant changes in migration velocity compared to wild-type controls. The decreased filopodial and lamellopodial activities, but not the decreased migration velocity, observed in Dscam11/Dscam105518 transheterozygous embryonic heart cardioblasts are enhanced by robo11 heterozygosity.
A robo1 homozygous background increases the percentage of embryonic segments displaying eg-positive axon midline crossing defects in flies expressing fraΔC.Scer\UAS.T:Ivir\HA1 under the control of Scer\GAL4eg-Mz360. However, this increase isn't considered statistically significant.
Removal of one copy of robo1 and sli (using the deficiency Df(2R)BSC482) suppresses the axon midline crossing defect found in Trim946 mutants.
A robo1 mutant genetic background does not affect the ability of ectopic Scer\GAL4ap-md544>leaScer\UAS.T:Ivir\HA1,T:SS-wg to direct the Scer\GAL4ap-md544-expressing axons to lateral pathways. In robo31, robo1 double mutants, the intermediate Fas2-positive tract fuses with the medial tract, and this thick fascicle crosses the midline. As in robo1 mutants, the Scer\GAL4ap-md544-expressing axons follow this fascicle across the midline. The lateral Fas2-positive tract remains in robo31, robo1 double mutants. Ectopic Scer\GAL4ap-md544>leaScer\UAS.T:Ivir\HA1,T:SS-wg is able to direct the Scer\GAL4ap-md544-expressing axons to extreme lateral positions even in a robo31, robo1 mutant genetic background.
The midline crossing errors seen in Fas2-expressing longitudinal axons of robo1 homozygous embryos are almost fully rescued if they are carrying one of robo::robo31.CC2.3.CC3.robo.T:Ivir\HA1 or robo::robo33.Ig2.1.Ig3.robo.T:Ivir\HA1. The midline crossing errors seen in Fas2-expressing longitudinal axons of robo1 homozygous embryos are not rescued if they are carrying one of learobo.T:Ivir\HA1, robo3robo.T:Ivir\HA1, robo::robo31.Ig2.3.Ig3.robo.T:Ivir\HA1, robo::robo31.TM.3.CC0.robo.T:Ivir\HA1, robo::robo31.CC0.3.CC1.robo.T:Ivir\HA1, robo::robo31.CC1.3.CC2.robo.T:Ivir\HA1 or robo::robo33.CC2.1.CC3.robo.T:Ivir\HA1. The midline crossing errors seen in Fas2-expressing longitudinal axons of robo1 homozygous embryos are partially rescued if they are carrying one of robo::robo33.TM.1.CC0.robo.T:Ivir\HA1, robo::robo33.CC0.1.CC1.robo.T:Ivir\HA1 or robo::robo33.CC1.1.CC2.robo.T:Ivir\HA1.
robo1/+ completely rescues the abnormal muscle phenotype caused by expression of LrtScer\UAS.T:Avic\GFP-EGFP under the control of Scer\GAL4sr-md710.
The EW neuron guidance defects in fraunspecified robo1 double mutants are less severe than fraunspecified single mutants.
Many of the dorsal abdominal clusters in robo1/learobo2-8 mutant animals have branches that exceed the normal level of extension at approximately 21 and 22 hours after egg laying, but this phenotype is not significantly greater than the defects observed in robo1 mutants.
Expression of fraScer\UAS.T:Ivir\HA1.cGa under the control of Scer\GAL4insc-Mz1407 does not suppress the ectopic commissural crossing phenotype seen in homozygous robo1 mutant embryos. Expression of fra::roboSD.Scer\UAS.T:SV5\V5,T:Zzzz\His6,T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4insc-Mz1407 almost completely rescues the ectopic commissural crossing phenotype seen in homozygous robo1 mutant embryos. Ectopic crossings are only seen in 20% of segments.
sli2, robo1/+ embryos show midline axon guidance defects, with on average two to three medial longitudinal fascicle ectopically crossing the midline per embryo.
Expression of fraΔC.Scer\UAS.T:Ivir\HA driven by Scer\GAL4elav.PLu in a fraunspecified robo1 double mutant background dramatically repels axons, though the defect is less severe than seen in a fraunspecified single mutant background. Expression of fraΔC.Scer\UAS.T:Ivir\HA driven by Scer\GAL4elav.PLu leads to a partial suppression of the robo1 single mutant neuronal phenotype.
Reduction of robo in a robo1 heterozygous background partially suppresses the elav5 mutant commissural phenotype. Thicker commissural tracts (relative to elav5 embryos) are made in more than 50% of the neuromeres.
Ts(1Lt;YSt)B118+Ts(1Rt;YLt)T9/Y partially suppresses the dMP2 axon misprojection phenotype seen in homozygous robo1 embryos, reducing the penetrance of the contralateral misprojection along the anterior commissure of the next segment from 99% to 61%. fra3 strongly suppresses the dMP2 axon misprojection phenotype seen in homozygous robo1 embryos, reducing the penetrance of the contralateral misprojection along the anterior commissure of the next segment from 99% to 24%. Expression of fraΔC.Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4insc-Mz1407, but not under the control of Scer\GAL415J2, restores the aberrant midline-crossing phenotype in these animals. The pCC and vMP2 midline-crossing phenotypes seen in homozygous robo1 embryos are partially and strongly suppressed by Ts(1Lt;YSt)B118+Ts(1Rt;YLt)T9 respectively. The pCC and vMP2 midline-crossing phenotypes seen in homozygous robo1 embryos are partially and strongly suppressed by fra3 respectively. Expression of fraΔC.Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4605 restores the aberrant midline-crossing phenotype in these animals. 23.8% of dMP2 neurons project contralaterally in sliGA20/robo1 transheterozygous embryos. This phenotype is suppressed by expression of sliScer\UAS.cKa under the control of Scer\GAL4605.
In robo1,sli2 /+,+ stage 16 embryos, FasII axons cross the midline in three to five segments per embryo. Expression of Nedd4Scer\UAS.T:Hsap\MYC under the control of either Scer\GAL4elav.PLu or Scer\GAL41407 does not enhance the midline crossing phenotype seen in transheterozygous sli2 robo1 stage 16 embryos. Expression of Nedd4EY00500 under the control of either Scer\GAL4elav.PLu or Scer\GAL41407 does not enhance the midline crossing phenotype seen in transheterozygous sli2 robo1 stage 16 embryos. Df(3R)ED4688 does not enhance the midline crossing phenotype seen in transheterozygous sli2 robo1 stage 16 embryos. Expression of enaScer\UAS.cCa under the control of Scer\GAL4elav.PLu suppresses the midline crossing phenotype seen in transheterozygous sli2 robo1 stage 16 embryos.
In robo1 learobo2-1 double mutants, the salivary gland guidance phenotype is enhanced. Glands are curved medially towards the midline, instead of lying parallel to the midline as in wild type.
robo1, learobo2-8 double mutants show severe myocardial cell misalignment including gaps, intercalation, and double rows.
35.9% of thoracic segments show transformation of the dch3 chordotonal organs to a morphology resembling that of abdominal lch5 chordotonal organs in robo1 leax135 double mutant embryos.
robo1 chb4 double heterozygous embryos have axons ectopically crossing the midline. Heterozygosity for learobo2-8 enhances the frequency of axons ectopically crossing the midline that is seen in robo1 chb4 double heterozygous embryos. Heterozygosity for robo31 does not enhance the frequency of axons ectopically crossing the midline that is seen in robo1 chb4 double heterozygous embryos. robo1 learobo2-8 double heterozygous embryos have axons ectopically crossing the midline.
robo1 robo31 double mutant embryos do not show defects in the position of the vmd1a neuron of the ventral multidendritic neuron cluster in the abdomen; a single vmd1a neuron is seen in each hemisegment. robo1 leaX123 double mutant embryos show defects in the position of the vmd1a neuron of the ventral multidendritic neuron cluster in the abdomen; in 21% of segments loss of the vmd1a neuron in a hemisegment is associated with duplication of the vmd1a neuron in the contralateral hemisegment. In addition, in 36% of segments, some vmd1a neurons are missing from the ventral vmd clusters (in most of these segments, the missing md neurons are probably located near the midline).
A few axon bundles cross the midline incorrectly in embryos trans-heterozygous for robo1 and sli1. This combination increases the penetrance of crossovers to about 60%. When one copy of Abl4 is also present in trans-heterozygous robo1 and sli1 embryos, several abnormal crossovers are observed in all embryos examined, and some axon bundles collapse towards the midline in a manner reminiscent of a sli1 phenotype. Heterozygous robo1 enhances the number of abnormal axon crossovers observed in Abl4 mutants. The addition of one mutant copy of Abl4 doubles the number of crossovers observed in heterozygous robo1 mutants. The presence of two copies of Abl4 in heterozygous robo1 mutants increases the penetrance of crossovers to 90%, with most embryos exhibiting three or more crossovers. In double homozygous robo1; Abl4 embryos, several axon bundles cross the midline abnormally as gaps and thinning of the longitudinal connectives become evident. Compared with heterozygous robo1 mutants alone, overexpression of AblScer\UAS.cHa using Scer\GAL4ftz.ng enhances the frequency of abnormal axonal crossovers. Compared with 26% of heterozygous robo1 mutants exhibiting inappropriate crossovers, expression of AblKN.Scer\UAS in the Scer\GAL4ftz.ng pattern results in almost all (95%) embryos exhibiting several axon bundles crossing the midline.
robo1 learobo2-8 double mutant embryos show misprojection of lch5 axons to the v'ch1 axon pathway in 11% of hemisegments (a similar frequency to robo1 single mutants). Stalling of the lch5 axons prior to turning point TP2, a characteristic of the learobo2-8 single mutant, is also seen in double mutant embryos, although at a higher frequency (6% of hemisegments). The dorsal cluster misprojection phenotype seen in learobo2-8 single mutant embryos is not seen in the robo1 learobo2-8 double mutant embryos; in the double mutant embryos the dorsal cluster axons follow a normal trajectory to the lateral region, although in 7% of hemisegments they grow abnormally from this point, either projecting along the v'ch1 route or growing intersegmentally. The lch5 cell bodies are located dorsal to their normal position in 11% of hemisegments and are aberrantly oriented in 3% of hemisegments of robo1 learobo2-8 double mutant embryos. Missing or aberrantly positioned spiracular branches and failure of motor axons to extend as far as the sensory neuron cluster are occasionally seen.
The addition of Rho1N19.Scer\UAS (driven by Scer\GAL4ftz.ng) to robo1/+ embryos enhances the midline crossover phenotype seen in the pCC/MP2 pathway axons. 89% of embryos exhibit the phenotype. An average of 3.1 crossovers are seen per embryo. The addition of Rho1V14.Scer\UAS (driven by Scer\GAL4ftz.ng) to robo1/+ embryos enhances the midline crossover phenotype seen in the pCC/MP2 pathway axons. 48% of embryos exhibit the phenotype. An average of 2.0 crossovers are seen per embryo. The addition of Rac1N17.Scer\UAS (driven by Scer\GAL4ftz.ng) to robo1/+ embryos has no effect on the midline crossover phenotype seen in the pCC/MP2 pathway axons. The addition of Rac1V12.Scer\UAS (driven by Scer\GAL4ftz.ng) to robo1/+ embryos enhances the midline crossover phenotype seen in the pCC/MP2 pathway axons. 100% of embryos exhibit the phenotype. An average of 6.5 crossovers are seen per embryo. The addition of Cdc42N17.Scer\UAS (driven by Scer\GAL4ftz.ng) to robo1/+ embryos partially suppresses the midline crossover phenotype seen in the pCC/MP2 pathway axons. 18% of embryos exhibit the phenotype. An average of 1.2 crossovers are seen per embryo. The addition of Cdc42V12.Scer\UAS (driven by Scer\GAL4ftz.ng) to robo1/+ embryos has no effect on the midline crossover phenotype seen in the pCC/MP2 pathway axons.
robo1/+ heterozygous embryos, in which expression of Gα49BQ203L.Scer\UAS is regulated under the control of Scer\GAL4ftz.ng, exhibit a significant increase in the number of midline crossovers (of axons expressing Fas2), as compared to robo1/+ mutant embryos and Gα49BQ203L.Scer\UAS;Scer\GAL4ftz.ng embryos (316/623 abdominal segments exhibit midline crossing in the combined mutant compared to 12/245 in robo1 and 86/427 in Gα49BQ203L.Scer\UAS;Scer\GAL4ftz.ng).
One copy of captk01217 enhances the frequency of midline crossing defects seen in robo1 learobo2-8 double mutant heterozygotes. One copy of capt10 does not enhance the frequency of midline crossing defects seen in robo1 robo31 double mutant heterozygotes.
The abnormal midline crossing of axons seen in robo1 heterozygotes is suppressed if the embryos are also heterozygous for one of chicsand-1, chicgdh-5 or chic221. However, chicsand-1 robo1 double homozygotes show a severe disruption of the nerve cord. Large numbers of axons cross the midline within segment boundaries and major gaps are seen in the longitudinal connectives.
87% of segments show crossing of the midline by muscles 6/7 in robo1 leaX123 double mutant embryos. This defect is rescued by expression of roboScer\UAS.cKa under the control of Scer\GAL4how-24B, but the axonal phenotype of these embryos is mutant. 6% of segments show crossing of the midline by muscles 6/7, 8% show abnormal insertion of muscle 5 and 11% show abnormal insertion of muscles 6/7 in sli2 robo1 double mutant embryos. 15% of segments show crossing of the midline by muscles 6/7, 31% show abnormal insertion of muscle 5 and 16% show abnormal insertion of muscles 6/7 in sli2 robo1 leaX123 triple mutant embryos.
Muscles 6 and 7 cross the midline in most segments in robo1 leaX123 double mutant embryos.
robo1 leaS4-14 double mutant embryos have a head phenotype comparable to that of leaS4-14 single mutants.
SosJC2 suppresses the axon crossing over phenotype seen in robo1 heterozygotes.
robo1, learobo2-5 embryos show an enhancement of the embryonic nervous system phenotype seen in these embryos. The pCC axon fasciculates with its contralateral homologue to extend anteriorly right along the midline. The aCC axons also frequently cross the midline in these embryos. By stage 16, all axons have joined the single midline bundle. Double mutants also exhibit a embryonic muscle phenotype. Ventral muscles normally attach to the epidermis beneath the lateral central nervous system (CNS). In robo1/learobo2-5 mutants, these muscles frequently extend across the dorsal surface of the CNS. Some muscles still attach to beneath the CNS though often somewhat close to the midline than usual. The addition of comm1 to robo1, learobo2-5 embryos has no effect on the ventral nerve cord phenotype. robo1/robo31 show an embryonic nervous system that is merely additive.
Ptp10D1; robo1/robo1; Ptp69D1/Ptp69D8ex25 triple mutant embryos have a severe phenotype in which most Fas2-positive axons converge on the midline. Some circles around the midline are still seen, but many axons fasciculate into a single thick bundle that extends along the midline. Vestiges of the lateral longitudinal pathways are seen in some segments.
Embryos heterozygous for both robo1 and sli2 show deviation of longitudinal fascicles towards the midline in 74% of segments. Embryos heterozygous for both robo1 and sliE-158 show deviation of longitudinal fascicles towards the midline in 32% of segments.
28% of segments contain Fas2-positive neurons inappropriately crossing the midline in sli1/robo1 double heterozygous embryos, in contrast to either single heterozygote which do not show this defect. 36% of segments contain Fas2-positive neurons inappropriately crossing the midline in sli2/robo1 double heterozygous embryos, in contrast to either single heterozygote which show defects in 1 or 0% of segments.
Xenogenetic Interactions
Statement
Reference
The ectopic midline crossing phenotype seen in the medial Fas2-positive axons in robo11 embryos is suppressed if they are expressing either Tcas\roboScer\UAS.T:Ivir\HA1,T:SS-wg or Tcas\robo2-3Scer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4elav.PLu, with nearly all segments being commissureless in these animals.
Expression of Mmus\Itpr1sponge.Scer\UAS.T:Avic\GFP under the control of Scer\GAL415J2 suppresses the dMP2 axon misprojection phenotype seen in homozygous robo1 embryos in 30% of axons. Expression of Mmus\Itpr1mut.sponge.Scer\UAS.T:Avic\GFP under the control of Scer\GAL415J2 does not suppress the dMP2 axon misprojection phenotype seen in homozygous robo1 embryos.
Compared with heterozygous robo1 mutants alone, expression of Abl::Hsap\ABL1::Hsap\BCRP210.Scer\UAS using Scer\GAL4ftz.ng enhances the frequency of abnormal axonal crossovers. Almost every segment of every robo1/+ embryo expressing Abl::Hsap\ABL1::Hsap\BCRP210.Scer\UAS exhibits abnormal crossovers. Expression of Abl::Hsap\ABL1::Hsap\BCRKR.Scer\UAS using Scer\GAL4ftz.ng enhances the midline-crossing phenotype of axon bundles in heterozygous robo1 embryos.
Fas2-positive axon bundles cross the midline in about 83% or 88% of robo1/+ embryos which are also expressing Ggal\MLCKct.Scer\UAS under the control of Scer\GAL4ftz.ng.
The number of embryos displaying abnormal midline crossing of axons increases from 5% in Khc::Ggal\MLCKKA.ftz heterozygotes to just over 60% if the embryos are also heterozygous for robo1.
The penetrance of the Fas2-positive axon crossover phenotype is increased in robo1 embryos that also carry Khc::Ggal\MLCKKA.ftz compared to either single mutant alone. A loss of integrity of the longitudinal connectives is seen in the robo1 Khc::Ggal\MLCKKA.ftz double mutant embryos and only remnants of the pCC/MP2 pathway are evident. The pioneer neurons of the pCC/MP2 and MP1 pathways cross the midline as they reach the anterior commissure in homozygous embryos. Axons of the MP1 cluster are also seen to cross the midline directly, join their sister neurons on the contralateral side and recross the midline at the anterior commissure. In embryos heterozygous for robo1 and carrying two copies of Khc::Ggal\MLCKKA.ftz, pioneer neurons of the pCC/MP2 and MP1 pathways will periodically cross the midline. Khc::Ggal\MLCKKA.ftz mediated stalls are still evident, but in addition, the pCC neuron will occasionally cross the midline and pioneer neurons within the MP cluster extend axons across the midline as observed in robo mutants. SosJC2 partially suppresses the interaction between robo1 and Khc::Ggal\MLCKKA.ftz.
Complementation and Rescue Data
Comments
The robo11 homozygous embryonic heart cardioblast defects (i.e. migration velocity and in filopodial and lamellopodial extensions and activities) and embryonic heart lumen formation defects are partially rescued by the expression of robo1Scer\UAS.cKa under the control of Scer\GAL4Mef2.247.
The defects in midline repulsion in the ventral nerve cord reflected by the ectopic midline axon crossings characteristic for robo11 homozygous mutant embryos is fully rescued by combination with any of the following: robo1T:Ivir\HA1, robo1ΔIg3.T:Ivir\HA1, robo1ΔIg4.T:Ivir\HA1 or robo1ΔIg5.T:Ivir\HA1, is partially rescued by expression of robo1ΔIg2.T:Ivir\HA1 and not affected by expression of robo1ΔIg1.T:Ivir\HA1 in the mutant background.
Expression of robo110xScer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4elav.PLu rescues the FasII-positive axon guidance defects of robo11/robo11 mutants, but also causes additional axon guidance defects, including disruption of normal commissure formation and disorganization of longitudinal axon pathways. Expression of robo1ΔIg1.Scer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4elav.PLu does not rescue the FasII-positive axon guidance defects of robo11/robo11 mutants. Expression of two copies of robo1T:Ivir\HA1, but not robo1ΔIg1.T:Ivir\HA1, rescues the ventral nerve cord defects, FasII-expressing axon guidance defects and pCC guidance defects of robo11/robo11 mutant embryos.
Expression of robo110xScer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4elav.PLu rescues the ectopic midline crossing phenotype seen in the medial Fas2-positive axons in robo11 embryos.
roborobo.T:Ivir\HA1 almost fully rescues the midline crossing errors seen in Fas2-expressing longitudinal axons of robo1 homozygous embryos.
The ectopic midline innervation phenotype found in robo1/robo2 mutants can be rescued by expression of roboScer\UAS.cKa under the control of Scer\GAL4eve.CQ2.
Expression of roboScer\UAS.T:Ivir\HA1,T:wg under the control of Scer\GAL4109(2)80 in robo1 mutant animals partially rescues the mutant dendritic overgrowth phenotype from 58% to 18%.
Expression of roboScer\UAS.T:SV5\V5,T:Zzzz\His6,T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4insc-Mz1407 almost completely rescues the ectopic commissural crossing phenotype seen in homozygous robo1 mutant embryos.
Expression of roboScer\UAS.T:Hsap\MYC under the control of Scer\GAL415J2 rescues the contralateral misprojection phenotype of dMP2 axons seen in robo1 embryos, while many surrounding neurons misproject contralaterally.
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Mutant
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Stocks (1)
Notes on Origin
Discoverer
Induced on: Fas3 null chromosome.
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Synonyms and Secondary IDs (9)
References (67)