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General Information
Symbol
Dmel\Dscam121
Species
D. melanogaster
Name
FlyBase ID
FBal0148065
Feature type
allele
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
Dscam21
Nature of the Allele
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 ( 1 )
Disease
Evidence
References
Modifiers Based on Experimental Evidence ( 0 )
Disease
Interaction
References
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
 
Phenotypic Data
Phenotypic Class
Phenotype Manifest In

anterior scutellar bristle & mechanosensory neuron | somatic clone

dendrite & abdominal dorsal multidendritic neuron ddaD (with Dscam123)

dendrite & abdominal dorsal multidendritic neuron ddaE (with Dscam123)

posterior dorsocentral bristle & mechanosensory neuron | somatic clone

posterior scutellar bristle & mechanosensory neuron (with Dscam1ΔR265)

posterior scutellar bristle & mechanosensory neuron (with Dscam1ΔR272)

posterior scutellar bristle & mechanosensory neuron | somatic clone

Detailed Description
Statement
Reference

Large Dscam121 Or47a and Gr21a neuron clones show axonal mistargeting defects; small/single cell Or47a clones still show axonal mistargeting defects.

Single cell analysis reveals a failure of Dscam121 mushroom body clone neurons to extend their axon branches dorsally and instead develop parallel horizontal branches.

Dscam123/Dscam121 transheterozygous embryos show defects in dendritogenesis in the embryonic aCC motoneurons (misplacement of primary branches) compared to controls. No gross morphology defects are observed in the MP1 neurons at early embryonic stage.

Dscam21 homozygous mutant third instar larvae show a mild but statistically significant increase in the proportion of dorsal midline ddaC dendrite length that is enclosed within the epidermis rather than attached to the ECM. The enclosed dendrite segments are often in the middle of stabilized dendritic branches. Most of the dendritic crossings seen in these mutants are between two dendrites that both contact the ECM and thus the dendrites are making contact.

Most Dscam121/Dscam1B17-1 mutants die at early larval stages, with the remainder dying before eclosion, and dendritic arborization neurons exhibit self-avoidance defects.

Surviving adults of Dscam121/Dscam1B17-1 mutants expressing Dscam1B1.4.2-6.18-9.22-17.1, Dscam1B2.4.2-6.18-9.22-17.2, Dscam1C1.4.2-6.14-9.24-17.1, Dscam1C2.4.2-6.14-9.24-17.2, both Dscam1B2.4.2-6.18-9.22-17.2 and Dscam1C1.4.2-6.14-9.24-17.1, or both Dscam1B1.4.2-6.18-9.22-17.1 and Dscam1C2.4.2-6.14-9.24-17.2, are largely immobile, have unexpanded wings, and die a few days after eclosion. The mushroom bodies in these adults exhibit abnormal morphology, with either no lobes or only one lobe projecting medially or dorsally.

Mutants show increased overlap and fasciculation of self-dendrites among dendritic arborization neurons in the larval body wall.

Less than 25% of Dscam21/Dscam23 larvae survive to late pupal stages.

Dscam21/Dscam23 embryos show defects in the organisation of the central nervous system, showing severely disrupted longitudinal tracts and some aberrant midline crossing.

Class I da neurons show defects in self-avoidance in Dscam21/Dscam23 larvae, such that in contrast to wild type, class I dendrites from the same cell overlap extensively and fasciculate in the mutant animals. Arbors of each cell project to the same general location as in wild type, but there are significant gaps in territory coverage.

Class IV da neurons in Dscam21/Dscam23 larvae show self-avoidance defects, but the tiling pattern is not obviously disrupted compared to wild type.

Dscam21 posterior Dorsocentral (pDc), anterior Scutellar (aSc) and posterior Scutellar (pSc) neuron clones enter the thoracic ganglion at the correct position but are unable to correctly target axonal branches and fail to elaborate any arbors. These neurons are able to form axonal branches but these remain clustered in a small bolus around a presumptive decision point. This phenotype is 100% penetrant for all tested neuron clones.

Small clones of Dscam21 cells induced in the mushroom body at the early third instar and then examined 24-36 hours later are seen as multiple fascicles in 15% of cases (in contrast to wild-type control clones which form single fascicles). Defects in branching are also seen in the mushroom body lobes; the mutant clones still form two distinct branches, but the branches fail to segregate dorsally and medially in 68% of cases.

Dscam21 mutant antennal olfactory receptor neurons often form discrete dense aggregates when they terminate in the glomeruli (in contrast to wild type, where the axons elaborate processes that extend throughout the glomeruli). Or47a-expressing olfactory receptor neurons (ORNs) that are mutant for Dscam21 show marked mis-targeting of axons in the antennal lobe, often failing to project to the normal target (glomerulus DM3) and instead innervating abnormal locations on the ipsilateral side. P{GAL4}GH298-expressing ORNs that are mutant for Dscam21 often fail to project to their normal target (the V glomerulus), innervating abnormal locations on the ipsilateral side. In 20% of cases none of the mutant fibres innervate the correct target. Single Dscam21 mutant Or47a-expressing ORNs exit the antennal nerve and often terminate in abnormal locations between glomeruli. Mutant terminals that do reach the appropriate glomerulus fail to elaborate the network of thin arbors characteristic of wild-type terminals. Single Dscam21 mutant P{GAL4}GH298-expressing ORNs show both ectopic targeting and defects in the morphology of terminals within the V glomerulus. Or22a-expressing and Or23a-expressing Dscam21 mutant ORNs target normally to the correct glomerulus, although they show a marked reduction in branches to the contralateral antennal lobe. Or47b-expressing Dscam21 mutant ORNs show mistargeting to more dorsal regions of the antennal lobe than the normal target (the VA1 l/m glomerulus) and also targeting defects in the contralateral lobe. Or46a-expressing Dscam21 mutant ORNs frequently terminate upon entering the ventral central nervous system before reaching the antennal lobe, either immediately prior to entering the suboesophageal ganglion or upon exiting it, just ventral to the antennal lobe.

External Data
Interactions
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Enhanced by
Statement
Reference

Dscam121/Dscam1[+], Spt-IB2 has abnormal neuroanatomy | adult stage phenotype, enhanceable by lace[+]/lace2

Suppressed by
Statement
Reference
NOT suppressed by
NOT Enhancer of
Statement
Reference

Dscam121/Dscam1[+] is a non-enhancer of abnormal neuroanatomy | dominant | adult stage phenotype of tapGal4

Other
Phenotype Manifest In
Enhanced by
Statement
Reference

Dscam121/Dscam1[+], Spt-IB2 has lobe system of adult mushroom body phenotype, enhanceable by lace[+]/lace2

Dscam121/Dscam1[+], Spt-IB2 has adult olfactory receptor neuron Or47a phenotype, enhanceable by lace[+]/lace2

Dscam121/Dscam1[+], Spt-IB2 has axon | adult stage phenotype, enhanceable by lace[+]/lace2

Suppressed by
NOT Enhancer of
Statement
Reference

Dscam121/Dscam1[+] is a non-enhancer of adult mushroom body beta-lobe | adult stage phenotype of tapGal4

Other
Additional Comments
Genetic Interactions
Statement
Reference

Spt-IB2, Dscam121, lace2 triple heterozygous adults show a moderate prevalence of mushroom body defects, namely a "lost-lobe" phenotype; Spt-IB2, Dscam121 double heterozygous adults do not show this defect.

Spt-IB2, Dscam121 double heterozygous adults also show Or47a neurons with axonal mistargeting defects; this defect is somewhat enhanced by additional lace2 heterozygosity.

Dscam121/+ does not significantly enhance frequency of mushroom body beta lobe axon overgrowth defects in tapGal4/+ brains.

Pak6-2;Dscam121 as well as dock04723;Dscam121 double heterozygous mutants display defects in dendritogenesis in the embryonic aCC motoneurons (decreased number of dendritic tips), which are not seen in either of the single heterozygotes.

Xenogenetic Interactions
Statement
Reference

Expression of both Hsap\DSCAML1Dscam1.WT and Hsap\DSCAMDscam1.WT, or both Hsap\DSCAMDscam1.WT and Dscam1B1.4.2-6.18-9.22-17.1, or both Hsap\DSCAMDscam1.WT and Dscam1C1.4.2-6.14-9.24-17.1, or both Hsap\DSCAML1Dscam1.WT and Dscam1B1.4.2-6.18-9.22-17.1, or both Hsap\DSCAML1Dscam1.WT and Dscam1C1.4.2-6.14-9.24-17.1, partially rescues the lethality of Dscam121/Dscam1B17-1 mutants, with an increased proportion of mutants developing to late pupal stage, and a small number of adults emerging.

Expression of Hsap\DSCAML1Dscam1.WT or Hsap\DSCAMDscam1.WT largely rescues the dendritic arborization neuron self-avoidance defects, and partially rescues the lethality of Dscam121/Dscam1B17-1 mutants, with an increased proportion of mutants developing to late pupal stage, and a small number of adults emerging. The majority of these adults are immobile and have unexpanded wings, and die a few days after eclosion. The mushroom bodies in these adults exhibit abnormal morphology, with either no lobes or only one lobe projecting medially or dorsally.

Expression of Hsap\DSCAMT.Dscam1.T:Avic\GFP or Hsap\DSCAML1T.Dscam1.T:Avic\GFP fails to rescue the larval lethality of Dscam121/Dscam1B17-1 mutants.

Expression of both Hsap\DSCAMDscam1.WT and Dscam1B2.4.2-6.18-9.22-17.2, or both Hsap\DSCAMDscam1.WT and Dscam1C2.4.2-6.14-9.24-17.2, or both Hsap\DSCAML1Dscam1.WT and Dscam1B2.4.2-6.18-9.22-17.2, or both Hsap\DSCAML1Dscam1.WT and Dscam1C2.4.2-6.14-9.24-17.2, substantially rescues the lethality of Dscam121/Dscam1B17-1 mutants, with a majority of mutants developing to late pupal stages.

Complementation and Rescue Data
Partially rescued by
Comments

The dendritogenesis defects (reduced number of dendritic tips) in the embryonic aCC motoneurons characteristic for Dscam123/Dscam121 transheterozygotes cannot be rescued by expression of Dscam1exon17.2.Scer\UAS.T:Avic\GFP under the control of Scer\GAL4eve.RN2 but is fully rescued when both Scer\GAL4eve.RN2 and Scer\GAL4GMR23E04 driver are used simultaneously - but only in the aCC that are associated with MP1 neurons expressing Dscam1exon17.2.Scer\UAS.T:Avic\GFP (Scer\GAL4GMR23E04 drives expression in a random half of all MP1 cells).

Expression of Dscam1A1.4.3-6.36-9.25-17.1, Dscam1A2.4.3-6.36-9.25-17.2, Dscam1B1.4.2-6.18-9.22-17.1, Dscam1B2.4.2-6.18-9.22-17.2, or both Dscam1B1.4.2-6.18-9.22-17.1 and Dscam1C1.4.2-6.14-9.24-17.1, or both Dscam1B2.4.2-6.18-9.22-17.2 and Dscam1C2.4.2-6.14-9.24-17.2, partially rescues the lethality of Dscam121/Dscam1B17-1 mutants, with an increased proportion of mutants developing to late pupal stage, and a small number of adults emerging.

Expression of Dscam1C1.4.2-6.14-9.24-17.1 partially rescues the lethality of Dscam121/Dscam1B17-1 mutants, with an increased proportion of mutants developing to late pupal stage, and a small number of adults emerging; and largely rescues the dendritic arborization neuron self-avoidance defects of Dscam121/Dscam1B17-1 mutants.

Expression of both Dscam1B1.4.2-6.18-9.22-17.1 and Dscam1B2.4.2-6.18-9.22-17.2, or both Dscam1B1.4.2-6.18-9.22-17.1 and Dscam1C2.4.2-6.14-9.24-17.2, or both Dscam1C1.4.2-6.14-9.24-17.1 and Dscam1C2.4.2-6.14-9.24-17.2, or both Dscam1B2.4.2-6.18-9.22-17.2 and Dscam1C1.4.2-6.14-9.24-17.1, almost completely rescues the lethality of Dscam121/Dscam1B17-1 mutants, with most mutants developing to pupal stage.

Expression of Dscam1C2.4.2-6.14-9.24-17.2 partially rescues the lethality of Dscam121/Dscam1B17-1 mutants, with an increased proportion of mutants developing to late pupal stage, and a small number of adults emerging, but fails to rescue the dendritic arborization neuron self-avoidance defects of Dscam121/Dscam1B17-1 mutants.

Expression of Dscam1C1T.4.2-6.14-9.24-17.1.T:Avic\GFP or Dscam1C2T.4.2-6.14-9.24-17.2.T:Avic\GFP fails to rescue the larval lethality of Dscam121/Dscam1B17-1 mutants.

Expression of transgenes that encode different isoforms of Dscam, under the control of Scer\GAL4elav.PLu, partially rescue the axonal targeting phenotype of Dscam21 mechanosensory clones. Both the Dscam1.34.30.2.Scer\UAS and Dscam7.6.19.2.Scer\UAS transgenes rescue primary axon extension posteriorly. Occasionally, Dscam1.30.30.2.A.Scer\UAS rescues the proximal, anterior-extending secondary axonal branch and a distal ipsilateral branch.

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Mutant
Wild-type
Stocks (0)
Notes on Origin
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External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (6)
References (16)