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General Information
D. melanogaster
FlyBase ID
Feature type
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
up, upheld1
Allele class
Nature of the Allele
Allele class
Mutations Mapped to the Genome
Additional Notes
point mutation
Nucleotide change:


Reported nucleotide change:



A to T nucleotide substitution in splice acceptor site.

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

Mutation at the 3' end of the intron preceding exon 10a. This results in mis-splicing of exon 10a. Two cryptic splice sites are used in the mutant, one in intron 9 (this generates an inserted sequence upstream of the normal splice site and will not maintain the normal reading frame of up) and one within exon 10a (this generates an in-frame deletion of the N-terminal amino acid residues encoded by exon 10a).

Nucleotide substitution: A?T.

Expression Data
Reporter Expression
Additional Information
Marker for
Reflects expression of
Reporter construct used in assay
Human Disease Associations
Disease Ontology (DO) Annotations
Models Based on Experimental Evidence ( 1 )
Modifiers Based on Experimental Evidence ( 0 )
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
Detailed Description

Raman spectroscopy reveals that, as muscle degeneration progresses with age, up1 mutant muscles show a significant increase in the levels of glycogen and carotenoids compared with wild-type controls.

The jump muscle output of 4 day old up1 flies (measured using displacement of an ergometer) is decreased compared to control flies.

Hemizygous males and homozygous females show a "wings-up" phenotype with a penetrance of 89-92% irrespective of temperature (18-29oC).

The jumping ability of up1 flies is poor from eclosion onwards and deteriorates further with age; 1-2 day old flies jump 1.4 +/- 0.77mm (compared to 22.8 +/- 3.3mm for controls), while by day 6 after eclosion few up1 flies can jump and by day 10, none of the mutant flies can jump. up1/+ flies can jump better than up1 flies but not as well as wild type and their jumping ability remains constant for at least 15 days after eclosion.

up1 has no effects on walking ability.

The thoraces of 3-5 day old up1 adults show partially contracted indirect flight muscles (IFMs) with some detachment of fibres. The severity of the IFM phenotype does not correlate with the wing position of the "wings-up" phenotype. The IFMs of homozygous flies lack the normal myofibrillar organisation when analysed ultrastructurally; the hexagonal lattice of thick and thin filaments is absent, except in a few places. Fuzzy, electron-dense structures that appear to be incompletely formed Z-lines are seen in most areas. Occasional myofibril like structures are seen, but they are narrower and shorter than normal adult sarcomeres and the Z-lines show streaming.

Myofibrils of the IFMs begin to assemble normally in up1 mutants, during early myofibril assembly, 42-44 hours after puparium formation (APF). The first defects appear to be separation of the fibres, usually from anterior attachment sites, starting at 80 hours APF.

The indirect flight muscles of up1/+ females appear normal at the light microscope level. Ultrastructurally, the IFM of 3-5 day old up1/+ flies show a more regular filament lattice and myofibrils are easily identified. Longitudinal sections show a continuous sarcomeric arrangement, but the Z-lines are wavy (this may represent a mild form of streaming). Filament bundles are often seen to extend from one myofibril to a neighbouring one. The myofibrils have a nonuniform cross section and peripheral filaments are incorporated into the central lattice.

100% of up1 adult males and 95% of adult females hold their wings vertically when raised at 29oC. The penetrance of this phenotype falls to 60% when flies are raised at 18oC. All up1 flies are flightless and have grossly abnormal muscles regardless of temperature.

up1 flies show 85% viability.

Flies are flightless and jumpless, while up1/+ females are flightless although their wings are held in a normal position and they are able to jump poorly. Some up1 flies show folded mesothoracic legs after recovery from etherization.

The flight musculature is mostly present in up1 flies but is grossly abnormal, although some cross-striations can be seen. The anterior part of the flight muscles is more severely affected than the posterior part and the tergal depressor of the trochanters (TDTs) are usually present, although abnormal and reduced in size. At no time during pupal development is the muscle present in normal quantities or with normal morphology.

RK1. Wings are held upright, parallel to each other.

All mutant flies raised at 29oC hold their wings in a vertical position, while 60% of those raised at 18oC hold their wings in a ventrolateral position (Deak, 1977); all flies are flightless and have abnormal muscles regardless of temperature. up1 shows more muscle abnormalities than up2. homozygote with abnormal wing phenotype heterozygote wing phenotype normal homozygote unable to fly heterozygote unable to fly RK1.

External Data
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Suppressed by

up1 has visible phenotype, suppressible by MhcR57-24.Act88F/Mhc10

Phenotype Manifest In
Suppressed by

up1 has wing phenotype, suppressible by MhcR57-24.Act88F/Mhc10

up1 has myosin filament & indirect flight muscle phenotype, suppressible | partially by MhcR57-24.Act88F/Mhc10

up1 has striated muscle thin filament & indirect flight muscle phenotype, suppressible | partially by MhcR57-24.Act88F/Mhc10

up1 has Z disc & indirect flight muscle phenotype, suppressible | partially by MhcR57-24.Act88F/Mhc10

Additional Comments
Genetic Interactions

up1/Y ; Mhc10/Mhc+ ; MhcR57-24.Act88F flies have a normal wing posture and a normal indirect flight muscle morphology under polarised light. Ultrastructurally, sarcomere-like assemblies with Z-bands and thick and thin filaments are seen, although in most areas the filaments appear disorganised.

Xenogenetic Interactions
Complementation and Rescue Data
Images (1)
Stocks (3)
Notes on Origin
External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (4)
References (9)