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General Information
Symbol
Dmel\robo1unspecified
Species
D. melanogaster
Name
FlyBase ID
FBal0086356
Feature type
allele
Associated gene
Associated Insertion(s)
Carried in Construct
Key Links
Mutagen
    Nature of the Allele
    Mutagen
    Mutations Mapped to the Genome
     
    Type
    Location
    Additional Notes
    References
    Associated Sequence Data
    DNA sequence
    Protein sequence
     
     
    Progenitor genotype
    Cytology
    Nature of the lesion
    Statement
    Reference
    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

    Stage 16 robounspecified embryos show thinning of the longitudinal connectives and thickening of the commissures. They exhibit a severe phenotype in which the medial fascicle repeatedly crosses the midline. Ap neurons also exhibit crossing defects but collapse on the midline.

    The medial longitudinal tracts inappropriately collapse at the midline in mutant embryos.

    All ganglionic branches migrate into the ventral nerve cord and the position of GB1 nucleus is not significantly affected in mutant embryos. At the midline, 29% of ganglionic branches cross the midline, while 26% migrate unusually close to the midline, where they stall or turn to migrate dorsally. The three longitudinal connectives are severely disrupted by loops of axons crossing the midline several times. GB1 crosses the midline only once and migrates along the longitudinal tracts of the contralateral hemisegment.

    The medial-most Fas2-positive fascicle collapses at the midline in mutant embryos.

    Loss of robo causes sever midline crossing of the midline, thickening of the commissures and reduction of the longitudinal connectives between segments. Con staining axons are show the expected pair of pathways, but axons in the medial of the two pathways appear to ectopically cross the midline. In a robounspecified mutant the axons in the medial Fas2 pathway cross and recross the midline, while the axons in the intermediate and lateral Fas2 pathways do not cross the midline.

    In embryos, far too many axons cross and recross the midline, resulting in commissures that are much thicker than wild-type and thinner longitudinal connectives.

    No gross dentritic defects are seen in mutant embryos.

    Fas2-positive nerve bundles frequently cross the midline in mutant embryos, in contrast to wild-type.

    robounspecified embryos have an increased number of axons in the commissures, coincident with a reduction of the number of axons in the longitudinal connectives. The commissures are thicker than normal and partially fused, while the longitudinals are thinner and pulled closer towards the midline than normal. The pCC growth cone extends anteriorly and then crosses the midline, where it fasciculates with its contralateral homologue. The pCC pathway projects back and forth across the midline, forming a circular pattern, in contrast to wild-type embryos where it projects longitudinally and does not cross the midline. The SP1 growth cone extends across the midline, adheres to the axon and cell body of its contralateral homologue, and turns to project anteriorly, as in wild-type embryos. However in robounspecified embryos, as the SP1 growth cone extends anteriorly into the next segment, it typically moves towards the midline and adheres to the axon of its contralateral homologue just on the other side of the midline. The SP1 axons freely cross and recross the midline in these embryos.

    External Data
    Interactions
    Show genetic interaction network for Enhancers & Suppressors
    Phenotypic Class
    Enhanced by
    NOT Enhanced by
    Statement
    Reference
    Suppressed by
    Enhancer of
    Other
    Phenotype Manifest In
    Enhanced by
    Statement
    Reference
    NOT Enhanced by
    Suppressed by
    NOT suppressed by
    Enhancer of
    Statement
    Reference

    robo1unspecified is an enhancer of fascicle phenotype of sli2

    Other
    Additional Comments
    Genetic Interactions
    Statement
    Reference

    kuzunspecified does not enhance the FasII axon midline crossing phenotype seen in robounspecified stage 16 embryos.

    Pan-neuronal expression of fra::roboU.Scer\UAS.T:Hsap\MYC under the control of Scer\GAL4elav.PLu partially suppresses the midline crossing phenotype seen in robounspecified mutants. Many of the most medial FasII axons still cross the midline.

    Pan-neuronal expression of fra::roboScer\UAS.FR.T:Hsap\MYC under the control of Scer\GAL4elav.PLu partially suppresses the midline crossing phenotype seen in robounspecified mutants. Many of the most medial ipsilateral axons still cross the midline.

    Expression of fra::roboU.Scer\UAS.T:Hsap\MYC in the ap neurons under the control of Scer\GAL4ap-md544 partially suppresses the midline crossing phenotype seen in robounspecified mutants. In some segments the ap axon tracts on either side of the midline are fused and collapsed on the midline.

    Expression of fra::roboScer\UAS.FR.T:Hsap\MYC in the ap neurons under the control of Scer\GAL4ap-md544 partially rescues the midline crossing phenotype seen in robounspecified mutants. Some segments have ap axon tracts on both sides of the midline.

    One copy of robounspecified enhances the ectopic midline crossing phenotype seen when kuzDN.Scer\UAS is expressed in the ipsilateral ap neurons of stage 16 embryos under the control of Scer\GAL4ap-md544.

    Expression of kuzDN.Scer\UAS in the ipsilateral ap neurons under the control of Scer\GAL4ap-md544 enhances the ectopic midline crossing phenotype seen in robounspecified/+ stage 16 embryos.

    The positioning of the longitudinal tracts in robounspecified ; NetAunspecified NetBunspecified double mutant embryos is as seen in NetAunspecified NetBunspecified single mutant embryos.

    Longitudinal tracts collapse at the midline in sliunspecified robounspecified double mutant embryos.

    21% of ganglionic branches stall outside the central nervous system in robounspecified leaunspecified double mutant embryos, 31% cross the midline and 45% are misrouted. The longitudinal axons collapse along the midline. The midline crossing phenotype of the ganglionic branches in robounspecified mutant embryos is not rescued by expression of leaScer\UAS.T:Ivir\HA1,T:wg under the control of Scer\GAL4bs.Term. Expression of sliScer\UAS.cKa under the control of Scer\GAL4twi.PG in a robounspecified background results in the formation of additional visceral branches from metamere T3 and also from other tracheal metameres.

    sli2 robounspecified double mutants exhibit midline guidance errors in 44% of embryonic segments (as assayed with Fas2). The heterozygote Df(1)NP5 phenotype is not enhanced in embryos also heterozygous for robounspecified. In contrast, the frequency of midline guidance errors is increased in robounspecified/+ embryos also heterozygous for Df(1)NP5.

    The frequency of ectopic crossing of the midline by axons in the central nervous system seen in robounspecified learobo2-4 embryos is increased by Abl2/+ or Abl4/+. The frequency of ectopic crossing of the midline by axons in the central nervous system seen in robounspecified learobo2-5 embryos is increased by Abl2/+. The frequency of ectopic crossing of the midline by axons in the central nervous system seen in robounspecified robo31 embryos is increased by Abl2/+.

    leaunspecified ; robounspecified double mutant embryos show an almost complete collapse of axon fascicles at the central nervous system midline. robounspecified homozygotes that are also heterozygous for kuzunspecified have a central nervous system (CNS) phenotype similar to that of robounspecified single mutants. The overall axon phenotype of robounspecified kuzunspecified double homozygotes is slightly more severe than that of robounspecified single mutants as axons are frequently detected running along the CNS midline.

    The addition of communspecified to robounspecified embryos does not affect the number of commissure crossing the midline.

    Injection of leacSa and leaa.cSa as dsRNA into robounspecified embryos results in embryos with only a single Fas2-expressing longitudinal fascicle, which runs along the midline. Injection of robo3cSa and robo3a.cSa as dsRNA into robounspecified embryos results in embryos with 2 Fas2-expressing longitudinal fascicles; the medial fascicle, which is thicker than normal as it contains axons that are normally part of the intermediate fascicle, and the lateral fascicle. The combined medial and intermediate fascicle ectopically crosses and recrosses the midline. The lateral fascicle remains ipsilateral.

    Embryos homozygous mutant for robounspecified and leaunspecified show a compressed midline where all the axons approach the midline and cannot leave. The addition of commΔe39 does not effect this phenotype. Embryos heterozygous for leaunspecified/+ and homozygous robounspecified, show ectopic crossing of the medial Fas2 pathway but the medial pathway collapses entirely onto the midline. Embryos heterozygous for robounspecified/+ and homozygous leaunspecified much more ectopic crossing is sen tha seen in leaunspecified homozygotes. In a robounspecified/commΔe39 double mutant embryo, the intermediate Fas2 pathways is also perturbed and can be seen crossing the midline.

    Xenogenetic Interactions
    Statement
    Reference
    Complementation and Rescue Data
    Comments

    Pan-neuronal expression of roboScer\UAS.T:Hsap\MYC under the control of Scer\GAL4elav.PLu partially rescues the midline crossing phenotype seen in robounspecified stage 16 embryos. Some ectopic crossing of FasII axons is still seen.

    Expression of roboScer\UAS.T:Hsap\MYC in the ap neurons under the control of Scer\GAL4ap-md544 rescues the midline crossing phenotype seen in robounspecified mutants.

    The characteristic robounspecified phenotype (crossing of the midline by Fas2-positive longitudinal axons) is not rescued if the embryos are also heterozygous for robolea.HR.T:Ivir\HA1.

    The characteristic robounspecified phenotype (crossing of the midline by Fas2-positive longitudinal axons) is not rescued if the embryos are also heterozygous for roborobo3.HR.T:Ivir\HA1.

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    Mutant
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    External Crossreferences and Linkouts ( 0 )
    Synonyms and Secondary IDs (2)
    Reported As
    Symbol Synonym
    robo1unspecified
    robounspecified
    Name Synonyms
    Secondary FlyBase IDs
      References (17)