Open Close
General Information
Symbol
Dmel\robo14
Species
D. melanogaster
Name
FlyBase ID
FBal0032591
Feature type
allele
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
roboz570, z570
Key Links
Nature of the Allele
Mutations Mapped to the Genome
 
Type
Location
Additional Notes
References
Nucleotide change:

G22697985A

Reported nucleotide change:

G1434A

Amino acid change:

W478term | robo1-PA; W478term | robo1-PC

Reported amino acid change:

W478term

Comment:

TGG to TGA nonsense mutation.

Associated Sequence Data
DNA sequence
Protein sequence
 
 
Progenitor genotype
Cytology
Nature of the lesion
Statement
Reference

Nucleotide substitution: G1434A.

Amino acid replacement: W478term.

Expression Data
Reporter Expression
Additional Information
Statement
Reference
 
Marker for
Reflects expression of
Reporter construct used in assay
Human Disease Associations
Disease Ontology (DO) Annotations
Models Based on Experimental Evidence ( 0 )
Disease
Evidence
References
Modifiers Based on Experimental Evidence ( 0 )
Disease
Interaction
References
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
 
Disease-implicated variant(s)
 
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
Detailed Description
Statement
Reference

robo14/Df(2R)BSC786 homozygous embryos exhibit severe defects in the longitudinal connective from 14h post-fertilization onwards, as compared to controls.

The intermediate and medial Fas2-positive longitudinal tracts are collapsed at the midline in mutant embryos.

48% of homozygous embryos hatch into first instar larvae and 3% of the embryos develop into the pupal stage, but none of these pupae eclose into adults.

robo4 embryos show much milder defects compared to robo4, leaX123 double mutant embryos: mispositioned cardioblasts are only occasionally seen.

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 19% 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 24% of hemisegments. Occasionally (1% of hemisegments), v'ch1 or other v' cluster axons grow dorsally before turning back into the segmental nerve or inappropriately joining the intersegmental nerve.

In robo4 homozygotes and robo4/Deficiency mutants GMC-1 and GMC1-1a are found to divide symmetrically to generate two RP2s and two aCCs at the expense of sib and pCC. The penetrance of the RP2 phenotype is about 2.3%.

robo4 mutants have a dramatically disrupted CNS axon scaffold, causing far too many axons to cross and recross the midline; anterior and posterior commissures appear to be much thicker or even fused together, and the longitudinal connectives are greatly reduced. The pCC neuron initially extends anteriorly, but instead of continuing its anterior trajectory as seen in wild-type, it turns and crosses the midline.

robo4 embryos form commissural tracts. Cell bodies of the RP3, RP2 and aCC neurons are present in all half-segments examined. Cell bodies of the RP2 and aCC neurons are displaced. Axon terminals are present on muscles 6 and 7 in 73% of half-segments, on muscle 12 in 76% of half-segments, muscle 2 in 90% of half-segments and muscle 1 in 98% of half-segments. The axon pathway of the RP3 neurons is normal in mutant embryos, and all RP3 neurons cross the midline, as in wild type. 19% of RP2 neurons cross the midline in mutant embryos, in contrast to wild-type embryos where they do not cross the midline. In all cases, subsequent growth cone guidance accuracy of the RP2 neurons is normal. 3% of aCC neurons cross the midline in mutant embryos, in contrast to wild-type embryos where they do not cross the midline. In all cases, subsequent growth cone guidance accuracy of the aCC neurons is normal.

Two many axons cross and recross the midline in the central nervous system (CNS) of robo4 embryos, resulting in thick and fuzzy commissures and longitudinals which are thinner than normal. Rarely, a single muscle can be seen extending inappropriately dorsally over the CNS. The ventral muscles are frequently attached more closely to the midline than in wild-type embryos.

"Fuzzy commisure" phenotype in embryonic central nervous system.

External Data
Interactions
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Enhanced by
Other
Phenotype Manifest In
Enhanced by
Enhancer of
Statement
Reference

robo[+]/robo14 is an enhancer of symmetrical commissure phenotype of enaGC1/ena210

robo[+]/robo14 is an enhancer of pCC neuron phenotype of enaGC1/ena210

robo[+]/robo14 is an enhancer of central nervous system phenotype of enaGC1/ena210

NOT Enhancer of
Statement
Reference
Suppressor of
Statement
Reference
NOT Suppressor of
Statement
Reference
Other
Additional Comments
Genetic Interactions
Statement
Reference

The defects in the longitudinal connective observed in late robo14/Df(2R)BSC786 homozygous embryos are severely enhanced by Df(2L)ED108 homozygosity.

robo4, fraunspecified double mutant embryos show a mixture of longitudinal tract phenotypes, ranging from a phenotype like that seen in the robo4 single mutant (collapsed tracts) to a phenotype like that seen in the fraunspecified single mutant (tracts positioned further away from the midline than normal) and an intermediate phenotype, although the robo-like phenotype is predominant.

Embryos mutant for both robo4 and leaX123 show defects in cardioblast and pericardial cell positioning and alignment, similar to slit2 embryos. The number of cardioblast nuclei that reach the dorsal midline in these embryos is approximately 86.2, compared to approximately 104 in wild type embryos.

Expression of leaScer\UAS.cSa in cardioblasts using Scer\GAL4Mef2.PR in a robo4 mutant background results in similar defects as when leaScer\UAS.cSa is expressed using Scer\GAL4Mef2.PR in an otherwise wild type background. Namely, a lateral shift of the row of cardioblasts away from the dorsal midline to a position normally occupied by pericardial cells while adhesion between these cells is maintained.

Embryos expressing leaScer\UAS.cSa under the control of Scer\GAL4Mef2.PR in a robo4, leaX123 double mutant background display gaps in rows of cardioblasts indicating a loss of adhesion between cardioblasts (as seen in robo4, leaX123 double mutants) as well as the mispositioning of these cells away from the dorsal midline (as seen in leaScer\UAS.cSa, Scer\GAL4Mef2.PR embryos).

Embryos expressing leaScer\UAS.cSa under the control of Scer\GAL4Mef2.PR in a robo4, leaX123 double mutant background exhibit mispositioning of cardioblasts away from the dorsal midline which is more severe as compared to expression of leaScer\UAS.cSa using Scer\GAL4Mef2.PR in an otherwise wild type background; cardioblasts are displaced even more laterally, with cardioblasts and pericardial cells even being observed in somatic muscle territory.

Expression of leaScer\UAS.cSa under the control of Scer\GAL4Mef2.PR in a robo4 mutant background results in a slight delay in dorsal closure: a slight gap between dorsal ectodermal cells is seen in late stage mutant embryos that is not observed in wild type embryos.

In RhoGAP93B1/RhoGAP93B1, robo4/+ embryos 9% of ganglionic branches cross the midline, as opposed to 1% in RhoGAP93B1 homozygotes alone. robo4 partially suppresses the ganglionic branch phenotype seen in Rac1J11, Rac2Δ embryos.

sli2/+ robo4/+ double heterozygotes have lch5 and lesA/ldaA axons misprojecting to the v'ch1 pathway in some hemisegments. No stalling of lch5 axons is seen and dorsal sensory axons have a normal morphology.

26% of segments contain Fas2-positive neurons inappropriately crossing the midline in sli1/robo4 double heterozygous embryos, in contrast to either single heterozygote which show defects in 0 or 1% of segments. 39% of segments contain Fas2-positive neurons inappropriately crossing the midline in sli2/robo4 double heterozygous embryos, in contrast to either single heterozygote which show defects in 1% of segments.

Xenogenetic Interactions
Statement
Reference
Complementation and Rescue Data
Images (0)
Mutant
Wild-type
Stocks (1)
Notes on Origin
Discoverer

Induced on: Fas3 null chromosome.

External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (8)
References (18)