Open Close
General Information
D. melanogaster
FlyBase ID
Feature type
Associated gene
Associated Insertion(s)
Carried in Construct
Key Links
Nature of the Allele
Mutations Mapped to the Genome
Additional Notes
Associated Sequence Data
DNA sequence
Protein sequence
Progenitor genotype
Nature of the lesion

Most of the Cby coding sequence has been deleted, by replacing a fragment that includes the acceptor splice site of Cby intron 1 plus most of Cby exon 2 with a mini-w marker flanked by loxP sites.

Insertion components
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 ( 0 )
Modifiers Based on Experimental Evidence ( 0 )
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
Disease-implicated variant(s)
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
Detailed Description

Homozygous Cby1 and hemizygous Cby1/Df(3R)BSC805 mutants are viable, but mutant males appear to be hypo-fertile.

When compared with wild-type, homozygous Cby1 and hemizygous Cby1/Df(3R)BSC805 mutants display negative geotaxis defects.

Homozygous Cby1 and hemizygous Cby1/Df(3R)BSC805 mutants display defects in mechanosensation. Compared with wild-type, the antennal sound-evoked potentials (reflecting mechanotransduction in the antennal chordotonal organs) are strongly reduced in the mutants. Further, whereas most of the control antennae show a pulsatile response, many of the Cby1 antennae lack any response.

Embryos in the offspring of homozygous Cby1 mutant parents do not show any cuticular defects. Bristle number and distribution in Cby1 adults appear normal compared to wild-type.

Comparison of wild-type and Cby1 mutant chordotonal organs on adult legs or antennae reveals that cilia are missing in about a third of the mutant scolopidia. When ciliary profiles are present, characteristic ultrastructural defects are observed that are never seen in controls. The most frequent defect is a reduced number of microtubule doublets. In rare cases, extra doublets are observed, or the symmetry of the axoneme is abnormal. The majority of the homozygous Cby1 chordotonal cilia are ultrastructurally normal.

In homozygous Cby1 mutant flies, some of the basal body structures of chordotonal neurons are completely missing. Either completely interrupted symmetry or more subtle discontinuities in the microtubule associated structures are observed at the level of the ciliary transition zone. Discontinuities in the transition zone can also be observed on longitudinal sections in addition to membrane bulges that are never observed in controls. Basal bodies, though present in all neurons, are not positioned properly at the base of the cilia in some Cby1 mutant neurons. The ultrastructural defects observed in Cby1 flies are incompletely penetrant.

Differential interference contrast microscopy of live squashes of testes from Cby1 mutant males show no cellular defects in spermatocyte-stage cysts: all are composed of 16 cells. The number of spermatids in each mature cyst is reduced from testes of Cby1 mutants as revealed by electron-microscopy. An altered number of spermatids is sometimes seen in early spermatid cysts, suggesting a possible meiotic defect, however, meiosis defects do not seem to be prevalent in Cby1 testes.

No significant variations are seen in the ratio of nuclei-to-mitochondrial (Nebenkern) derivatives in Cby1 mutant onion-stage cysts, even though some aberrant spermatids can sometimes be observed.

In early Cby1 spermatid sections, mitochondrial derivatives with no axoneme can be observed, as well as axonemes with no visible mitochondria derivatives, which are never observed in controls. The axonemal ultrastructure in Cby1 mutants is characterised by partially penetrant but reproducible defects. Incomplete axonemal structures are found with a reduced number of microtubule doublets in the mutants.

External Data
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Phenotype Manifest In
Additional Comments
Genetic Interactions

dila81;Cby1 double mutant flies are completely uncoordinated and show ultrastructural defects in chordotonal organ of the second antennal segment: cilia are mostly missing - the few remaining ones are severely disorganized and although both basal bodies (proximal and distal) are present, no transition zone is formed. The males are completely sterile, produce no mature sperm, their sperm cysts fail to elongate (but the overall size of their testes is not reduced) and show severe ultrastructural defects: Most of the axonemes are missing or damaged, the centrioles of late spermatocytes do not form a primary cilium-like structure, fail to dock to the plasma membrane, have an abnormal orientation in the cell, no ciliary cap is observed in these spermatocytes and premature axoneme elongation occurs.

Xenogenetic Interactions
Complementation and Rescue Data
Rescued by

The negative geotaxis phenotype of Cby1 mutants is rescued by one copy of N+t40.

Images (0)
Stocks (0)
Notes on Origin
External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (2)
Reported As
Name Synonyms
Secondary FlyBase IDs
    References (3)