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General Information
Symbol
Dmel\ifB4
Species
D. melanogaster
Name
FlyBase ID
FBal0039417
Feature type
allele
Associated gene
Associated Insertion(s)
Carried in Construct
Mutagen
Nature of the Allele
Mutations Mapped to the Genome
 
Type
Location
Additional Notes
References
deletion
Comment:

Reported as a deletion in the if gene encompassing 1036 bases of intron 8 and 577 bases of exon 9.

Associated Sequence Data
DNA sequence
Protein sequence
 
 
Progenitor genotype
Cytology

Polytene chromosomes normal.

Nature of the lesion
Statement
Reference

1036 bp has been deleted from intron 8 and 577bp deleted from exon 9. The exon 9 splice acceptor is lost, and most of the potential cryptic splice acceptors would result in a frameshift and premature termination.

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 )
 
Phenotypic Data
Phenotypic Class
Phenotype Manifest In

muscle attachment site & basal lamina

muscle attachment site & connecting hemi-adherens junction

muscle attachment site & muscle tendon junction

Detailed Description
Statement
Reference

ifB4 follicle cell clones do not display any defects. In some cases, all follicle cells are mutant for ifB4, and the oocyte is still normally elongated.

In mutant embryos, the visceral branches of the tracheal system are shorter than wild-type, though fine branches still exist. During development, they reach and contact the visceral mesoderm, but do not migrate along the mesoderm.

Muscles are detached in stage 17 mutant embryos and are rounded up or spindle shaped. Detachment of the muscle plasma membrane from the extracellular matrix-containing attachment site is seen, although the muscle actin filaments are still anchored to the membrane.

The continuous layer of visceral mesoderm that normally surrounds the gut is severely disrupted in homozygous embryos.

Endodermal midgut cells of homozygous embryos show a modest delay of approximately 30 minutes in midgut migration, so that anterior and posterior midgut cells do not contact each other until stage 13 when wild-type cells have already fused. The endodermal cells still send projections towards the visceral mesoderm, as in wild type. The arrangement of the visceral mesoderm cells is abnormal in homozygous embryos.

Embryos exhibit normal epidermis and resultant secreted cuticle, defects lie in internal tissues. Somatic muscle detach and round up. Gut morphogenesis is defective: anterior midgut does not become a slender tube and only two fat gastric caecae are formed. The ventral nerve cord does not fully condense. Mitotic clones in the wing produce bubbles.

Homozygous embryos show a muscle detachment phenotype. The gut musculature is severely disrupted, the proventriculus is abnormal with the inner layer having been pulled out, and only two blunt gastric caecae are seen.

Attachment of muscles to the epidermis is disturbed in stage 16 homozygous embryos. The majority of connecting hemiadherens junctions (HAJs) are detached from their partner in stage 17 embryos, and the tendon HAJs detach from the tendon matrix. The tendon matrix is detached from both the muscle and epidermal cells in these embryos. The basement membrane is closely apposed to the epidermal HAJs. The basement membrane is detached from 50% of focal HAJs.

Hemizygous embryos have detached somatic muscles. The midgut remains as a large sac in stage 17 hemizygous embryos, and only two blunt gastric caecae are present.

Small clones (fewer than 150 cells) in the wing are often wild type or have a weak phenotype, even if on the ventral surface.

Dorsal herniation is observed in homozygotes but not in double mutant combinations with mewH7, mewM6, mew498 and mew81. Clones in the eye do not exhibit photoreceptor disorganisation.

Clonal analysis reveals that lack of if has no discernible effect on germ cell development. Mutant embryos show a distinct and reproducible separation between the ectodermal and mesodermal tissue layers of the germband, though the separation is not complete. Midgut primordia meet and initiate fusion at least 1 to 2 hours after wild type embryos would. Visceral mesoderm shows gaps and irregularities. Midgut constrictions partially form.

Midgut constrictions form normally, but defects become evident when the gut elongates, when the visceral muscle detaches and forms clumps. Only two, broad gastric caecae form. The proventriculus is normal. The anterior portion of the midgut remains large, resulting in a spherical yolk-filled sac at the anterior of the midgut, though the posterior end narrows in diameter. By the end of stage 16 a few muscle detach, generally lateral longitudinal muscle muscles 4, 12 and transverse muscle 8. The ventral nerve cord only partially contracts.

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

ifB4 has muscle attachment site & basal lamina phenotype, enhanceable by mewunspecified

NOT Enhanced by
Statement
Reference

if3/ifB4 has wing phenotype, non-enhanceable by pot[+]/potP3

Suppressed by
NOT suppressed by
Other
Additional Comments
Genetic Interactions
Statement
Reference

Expression of mewScer\UAS.cMBa in ifB4 follicle cell clones (using the MARCM method) results in a delay in the developmental reorientation of stress fibres.

mys10 ifB4 double mutant embryos show dorsal herniation.

Some muscles in ifB4 Df(2R)enE embryos have abnormal free ends.

The midgut phenotype is enhanced in ifB4 mewM6 double mutant embryos. Expression of mewScer\UAS.cMBa under the control of both Scer\GAL4twi.PG and Scer\GAL4how-24B fails to rescue the visceral mesoderm phenotype of ifB4 embryos. ifB4 scb2 double mutant embryos show no difference in midgut development compared to ifB4 single mutant embryos.

ifB4 mewunspecified double mutant embryos have a more severe muscle detachment phenotype than ifB4 single mutant embryos. The basement membrane detaches or fails to assemble in epidermal HAJs in these embryos. ifB4 LanA9-32 double mutant embryos show each of the defects seen in ifB4 or LanA9-32 single mutant embryos, and in addition show loss of basement membrane adhesion to the epidermal HAJs.

The frequency of wing blisters seen in if3/ifB4 flies is not dominantly enhanced by potP3.

The embryonic lethality of ifB4 homozygotes is fully rescued by if::mewScer\UAS.cMBa, expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG. The embryonic lethality of ifB4 homozygotes is not rescued by mewScer\UAS.cMBa or mewScer\UAS.cMBb expressed using Scer\GAL4how-24B, although it is rescued in approximately 1/3 of cases by mewScer\UAS.cMBa or mewScer\UAS.cMBb expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG. The embryonic lethality of ifB4 homozygotes is rescued in approximately 1/3 of cases by if::mewScer\UAS.cMBb expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG. The detached muscle phenotype is partially rescued by mewScer\UAS.cMBa expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG. Muscles in these partially rescued embryos appear spindle shaped rather than rectangular, and gaps are therefore seen between the ends of the ventral longitudinal muscles.Scer\GAL4twi.PG ifB4/+ ; Scer\GAL4how-24B mewScer\UAS.cMBa embryos have normal muscle attachments. The midgut phenotype is partially rescued by mewScer\UAS.cMBa expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG.

Double mutants for mew and if have a midgut phenotype as severe as that of mys mutants. Muscles detach, but later in development than in mys mutants. Dorsal hole and U-shaped cuticle of mys mutants are not observed in mew or if mutants. Double mutants between mew498, mew023 or mewM6 and ifk27e or ifB4 do not show the twisted germband, amnioserosal detachment, dorsal movement of germband, dorsal hole and U-shaped embryo phenotypes of mys mutants, but do show early muscle detachments, as seen for mys mutants.

Xenogenetic Interactions
Statement
Reference
Complementation and Rescue Data
Not rescued by
Comments

ifScer\UAS.cMBa rescues the visceral mesoderm defects of ifB4 embryos when expressed under the control of both Scer\GAL4twi.PG and Scer\GAL4how-24B.

Embryonic lethality, the muscle detachment phenotype, and the proventriculus and gastric caeca defects are completely rescued by ifScer\UAS.cMBa expressed under the control of both Scer\GAL4how-24B and Scer\GAL4twi.PG. Embryonic lethality is almost completely rescued by ifΔGFFNR.Scer\UAS expressed under the control of both Scer\GAL4how-24B and Scer\GAL4twi.PG. The muscle detachment phenotype is almost completely rescued in these embryos, with just one muscle detached in 15% of the embryos. Ectopic muscle attachment sites are seen in some of these embryos. The gastric caeca defect is completely rescued in these embryos, and the visceral mesoderm is only mildly disrupted. The proventriculus defect is not rescued. Embryonic lethality is not rescued by ifΔcyt.Scer\UAS expressed under the control of both Scer\GAL4how-24B and Scer\GAL4twi.PG. The muscle detachment phenotype is rescued in these embryos. However, the transverse muscles appear broader at their tips than normal, and the ventral lateral muscles form ectopic muscle attachments with the ventral acute muscles in many of the embryos, usually in segments A2 to A5. The gastric caeca defect is completely rescued in these embryos, and the visceral mesoderm is only mildly disrupted. The proventriculus defect is not rescued.

The embryonic lethality of ifB4 homozygotes is fully rescued by ifScer\UAS.cMBa expressed using Scer\GAL4how-24B, although the larvae produced die before pupation. The embryonic lethality of ifB4 homozygotes is fully rescued by ifScer\UAS.cMBa, ifC.Scer\UAS or ifm8.Scer\UAS expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG. The detached muscle phenotype is fully rescued by ifScer\UAS.cMBa expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG. The midgut phenotype is fully rescued by ifScer\UAS.cMBa expressed using Scer\GAL4how-24B in conjunction with Scer\GAL4twi.PG.

Images (0)
Mutant
Wild-type
Stocks (0)
Notes on Origin
Discoverer

Selected as: F1 screen for mutations that fail to complement if3.

Comments
Comments

Class 0 mutation.

Embryos mutant for if both zygotically and maternally undergo germ band retraction normally and form a normal epidermis.

External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (1)
Reported As
Name Synonyms
Secondary FlyBase IDs
    References (27)