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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
    Nucleotide change:


    Reported nucleotide change:


    Amino acid change:

    W87term | brk-PA

    Reported amino acid change:



    TGG to TAG nonsense mutation in codon Trp87.

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

    Amino acid replacement: ?88term.

    The encoded protein contains only 10% of the normal amino acid sequence.

    Nucleotide substitution: G790A.

    Amino acid replacement: W87term.

    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

    Flies bearing brkM68 somatic clones display wing notches and swirled hair in the vicinity of the notches but only occasionally wing outgrowths.

    The boundary between the maxillary and mandibular segments is unaffected in brkM68 embryos.

    Eggs from females carrying large homozygous somatic follicle cell clones completely lack dorsal appendages.

    Somatic clones in the follicle cells of the egg chamber result in eggs with an enlarged operculum and reduced dorsal appendages.

    Ectopic veins form along the inner edges of somatic clones of brkM68 homozygous cells located in positions posterior to wing vein L5. When such clones are located anterior to L2 ectopic vein is also induced along the boundary, but both inside and outside the clone. Ectopic venation is not associated with clones found elsewhere in the disc.

    brkM68 somatic clones often from outgrowths in adult wings. The patterning of these outgrowths is similar to an continuous with the part of the wing from which they arise - unlike outgrowths due to clonal expression of dpp, mirror image duplication of pattern in these outgrowth is never seen. The clones producing outgrowths are restricted to the lateral regions of the wing disc whereas those in the central region are of normal size. Lateral clones are morphologically distinct in the late third instar wing disc, and show increased BrdU incorporation levels. There is an increase in apoptosis at the boundaries of brkM68 somatic clones in the wing pouch of third instar wing discs.

    Mutant embryos show mislocalisation of crystal cells to more posterior positions in the embryo than normal.

    Females containing homozygous germline clones produce wild-type egg chambers and germline stem cells are stable for at least two weeks after clone induction.

    Homozygous embryos have normal numbers of abdominal peripheral nervous system neurons in the dorsal and lateral clusters, but fewer in the ventral clusters.

    Mutant larvae have narrowed denticle belts which contain about three disordered rows of tapered denticles, which all point to the posterior. The belts usually consist of one row of large denticles followed by two rows of tiny denticles.

    In embryos laid by homozygous mutant mothers the leading edge specification is normal.

    In mutant larvae a denticle belt phenotype similar to that seen in brkF124 larvae is seen. In mutant embryos a loss of neuroblast phenotype similar to that seen in brkF124 embryos is seen.

    Embryos show expanded dorsal epidermis at the expense of ventral epidermis. This phenotype resembles that caused by ectopic expression of dpp or of constitutively activated tkv. Mutant clones in the wing disc produce outgrowths and pattern duplications in anterior and posterior regions of the wing. The outgrowths are entirely cell autonomous. Outgrowths are often accompanied by notches, in a similar phenotype to that caused by constitutively activated tkv, though detailed examination of the outgrowths suggests that loss of brk produces a lower level of activation than that caused by constitutively activated tkv.

    The ventral denticle belts have largely disappeared due to an expansion of the dorsal epidermis carrying dorsal hairs in brkM68/Y embryos. The number of sna-expressing neuroblasts in the ventral neurogenic region is reduced. The number of amnioserosa cells is normal. The phenotype is not enhanced in embryos derived from females carrying homozygous brkM68 germline clones.

    External Data
    Show genetic interaction network for Enhancers & Suppressors
    Phenotypic Class
    Suppressed by
    NOT suppressed by
    Suppressor of
    Phenotype Manifest In
    Enhanced by

    brkM68 has denticle belt phenotype, enhanceable by tsh8

    NOT suppressed by

    brkM68 has ventral abdominal cluster phenotype, non-suppressible by shn1

    Enhancer of

    brkM68 is an enhancer of denticle belt phenotype of tsh8

    NOT Enhancer of

    brkM68/brkM68 is a non-enhancer of wing vein phenotype of biD4

    Suppressor of
    NOT Suppressor of

    brkM68/brkM68 is a non-suppressor of wing vein phenotype of biD4

    Additional Comments
    Genetic Interactions

    Eggs laid by brkM68/+ ; Snoo174/Snoo174 females are shorter in length and have a significantly larger operculum than normal. The dorsal appendages are stout and massively thick at their ends.

    The mesoderm is able to spread out over the ectoderm after mesoderm invagination in sogY506 brkM68 double mutant embryos. The mesoderm is able to spread out over the ectoderm after mesoderm invagination in Egfrtop-18A sogY506 brkM68 triple mutant embryos.

    biD4, brkM68 double homozygous somatic clones in the wing either contain no veins at all, or contain short fragments of ectopic vein that do not follow clone boundaries.

    Overgrowth of brkM68 somatic clones in lateral regions of wing discs is not suppressed in DadScer\UAS.cTa; Scer\GAL4nub-AC-62 animals.

    shn1 brkM68 double mutant embryos show a clear rescue of the number of neurons in the dorsal and lateral clusters of the peripheral nervous system compared to shn1 single mutants. The reduction in the number of neurons in the ventral clusters in shn1 brkM68 double mutant embryos is indistinguishable from that in brkM68 single mutants.

    brkM68 tsh8 double mutant larvae show an essentially naked cuticle phenotype, with only single tiny denticles occasionally seen scattered in the posterior abdomen.

    brkM68 clones induced in a dppd8/dppd12 background lead to outgrowths of wing blade material indicating that normal target gene activation occurs without normal dpp levels.

    The ectoderm of brkM68 sogY506/Y double mutant embryos forms only dorsal-type cuticle hairs and completely lacks ventral denticles. The ventral neurogenic region is deleted. The amnioserosa defect seen in sogY506/Y single mutant embryos is not rescued in the double mutant embryos. brkM68; dppH46 sna18 Df(2R)twi quadruple mutant embryos secrete cuticles showing partial transformation of ventral into dorsal epidermis.

    Xenogenetic Interactions
    Complementation and Rescue Data
    Images (0)
    Stocks (1)
    Notes on Origin
    External Crossreferences and Linkouts ( 0 )
    Synonyms and Secondary IDs (6)
    References (41)