Nucleotide substitution: G?A.
Amino acid replacement: W97term.
Amino acid replacement: E97term.
G23792195A
G?A
W97term | mbc-PA; W97term | mbc-PB
W97term
TGG to TGA nonsense mutation in codon Trp97.
Mutant stage 16 embryos show a severe myoblast fusion defect in the dorsal pharyngeal muscle.
In homozygous mutant embryos, myoblasts are competent to migrate to the founder cells, but fusion does not occur.
Homozygous embryos exhibit breaks in the outer longitudinal fascicles and a collapse of axons onto the MP1 fascicle tracts. Thinning of the longitudinal axon tracts and abnormal spacing between segments is also observed.
Unfused myoblasts are apparent in stage 16 homozygous embryos. Although the majority of founder cells examined remain mononucleate, a limited amount of fusion does occur, as binucleate muscle precursors that have undergone a single fusion event between a founder cell and a fusion competent myoblast (FCM) are seen in the mutant embryos. The muscle founders analysed and the percentage of segments in which the founder cell remains mononucleate are as follows: DA1 (72.1%), DO1 (76.3%), LO1 (90.2%), LT2 (93.4%), LT4 (95.0%), VT1 (78.9%), VA2 (84.6%). The overall level of myoblast fusion in embryos lacking both maternal and zygotic function is roughly comparable to that seen in zygotic mutant embryos.
The F-actin foci which are seen in wild-type FCMs at points of contact with developing myofibers are less dense and somewhat dispersed in homozygous FCMs. In addition, the actin cytoskeletal network of the mutant FCMs is different from wild type, with many of the mutant cells showing a complete collapse of the network.
The extent of myoblast fusion in mbcD11.2 mutant embryos is significantly reduced compared to wild type.
Homozygous embryos do not show any apparent defects in macrophage migration.
When mutant somatic clones are made in border cells, a strong effect is seen on border cell migration. At stage 10 only about 10% of mutant border cell clusters reach the oocyte.
mbcD11.2 has abnormal neuroanatomy | embryonic stage phenotype, enhanceable by spg2
mbcD11.2 has abnormal neuroanatomy | embryonic stage phenotype, non-enhanceable by Df(2L)CadNΔ14
mbcD11.2 has embryonic myoblast phenotype, non-enhanceable by spg2
mbcD11.2 has lateral longitudinal fascicle phenotype, non-enhanceable by spg2
mbcD11.2 has lateral longitudinal fascicle phenotype, non-enhanceable by Df(2L)CadNΔ14
mbcD11.2 has embryonic myoblast phenotype, suppressible by Rac1V12.UAS/Scer\GAL4sns.PK
mbcD11.2 has embryonic myoblast phenotype, non-suppressible by Scer\GAL4kirre-rP298-G4/Rac1V12.UAS
mbcD11.2 has embryonic myoblast phenotype, non-suppressible by Scer\GAL4sns.PK/Rac1UAS.cLa
mbcD11.2/mbc[+] is an enhancer of visceral muscle fiber | embryonic stage phenotype of msk4/msk5
mbcD11.2 is an enhancer of mesonotum phenotype of PvrRNAi.UAS, Scer\GAL4pnr-MD237
mbcD11.2 is an enhancer of thorax phenotype of PvrRNAi.UAS, Scer\GAL4pnr-MD237
mbcD11.2/mbc[+] is a suppressor of visceral muscle fiber | embryonic stage phenotype of Scer\GAL4twi.PU, mskUAS.cLa
mbcD11.2/mbc[+] is a suppressor of eye phenotype of Ced-12UAS.cGa, Scer\GAL4Mef2.PR, mbcUAS.cBa
mbcD11.2 is a suppressor of centripetally migrating follicle cell & actin filament phenotype of Pvrλ.UASp.Tag:MYC, Scer\GAL4slbo.2.6
mbcD11.2 is a suppressor of centripetal follicle cell phenotype of Pvrλ.UASp.Tag:MYC, Scer\GAL4slbo.2.6
mbcD11.2, spg2 has larval ventral nerve cord | embryonic stage phenotype
The presence of mbcD11.2/+ increases the severity of muscle attachment defects in msk4/msk5 embryos.
mbcD11.2/+ largely suppresses the muscle detachment phenotype of Scer\GAL4twi.PU mskScer\UAS.cLa embryos.
In mbcD11.2/mbcD11.2, spg2/spg2 double mutants, myoblasts fail to fuse but still cluster around the founder cells (as in mbcD11.2/mbcD11.2 mutants).
There is no significant increase in broken fascicles or the collapse of the outer longitudinal tracts in mbcD11.2, spg2 double mutants over mbcD11.2 mutants alone. However, there is an increase in midline fascicle crossing in the double mutants. Abnormal positioning of the ventral nerve cord is also observed in the double mutants.
mbcD11.2, Df(2L)CadNΔ14 embryos do not show increased axonal outgrowth or guidance defects compared to mbcD11.2 embryos.
Expression of Rac1V12.Scer\UAS under the control of Scer\GAL4sns.PK rescues myoblast fusion in homozygous mbcD11.2 embryos such that the somatic muscle pattern is almost wild type.
Expression of Rac1V12.Scer\UAS under the control of Scer\GAL4kirre-rP298 does not rescue myoblast fusion in homozygous mbcD11.2 embryos.
Expression of Rac1Scer\UAS.cLa under the control of Scer\GAL4sns.PK does not rescue myoblast fusion in homozygous mbcD11.2 embryos.
mbcD11.2 spg2 double mutant embryos have a roughly comparable overall level of myoblast fusion compared to mbcD11.2 single mutant embryos.
The rough eye phenotype resulting from Scer\GAL4GMR.PU-mediated expression of Ced-12Scer\UAS.cGa and mbcScer\UAS.cBa is suppressed by heterozygosity for mbcD11.2.
mbcD11.2 is rescued by mbcUAS.Tag:HA/Scer\GAL4sns.PK
mbcD11.2 is rescued by mbcNPxxP.Δ1807.UAS.Tag:HA/Scer\GAL4sns.PK
mbcD11.2 is rescued by mbcUAS.Tag:HA/Scer\GAL4twi.PG
mbcD11.2 is rescued by Scer\GAL4twi.PG/mbcCBS.UAS
mbcD11.2 is rescued by Scer\GAL4twi.PG/mbcΔ1807.UAS.Tag:HA
mbcD11.2 is rescued by mbcNPxxP.UAS.Tag:HA/Scer\GAL4twi.PG
mbcD11.2 is rescued by Scer\GAL4twi.PG/mbcNPxxP.Δ1807.UAS.Tag:HA
mbcD11.2 is rescued by Scer\GAL4twi.PG/mbcΔPRM.UAS.Tag:HA
mbcD11.2/Df(3R)mbc9 is rescued by mbcUAS.Tag:HA/Scer\GAL4how-24B
mbcD11.2/Df(3R)mbc9 is rescued by Scer\GAL4how-24B/mbcCBS.UAS
mbcD11.2/Df(3R)mbc9 is rescued by Scer\GAL4how-24B/mbcNPxxP.Δ1807.UAS.Tag:HA
mbcD11.2/Df(3R)mbc9 is rescued by Scer\GAL4how-24B/mbcΔPRM.UAS.Tag:HA
mbcD11.2 is not rescued by mbcUAS.Tag:HA/Scer\GAL4kirre-rP298-G4
mbcD11.2 is not rescued by mbcUAS.Tag:HA/Scer\GAL4kirre-rP298-G4
mbcD11.2 is not rescued by Scer\GAL4twi.PG/mbcSH3W47K.UAS.Tag:HA
mbcD11.2 is not rescued by Scer\GAL4twi.PG/mbcDockerF6.4.UAS.Tag:HA
mbcD11.2 is not rescued by Scer\GAL4twi.PG/mbcΔDHR1.UAS.Tag:HA
mbcD11.2/Df(3R)mbc9 is not rescued by Scer\GAL4how-24B/mbcΔDHR1.UAS.Tag:HA
Expression of either mbcScer\UAS.T:Ivir\HA1 or mbcNPxxP.Δ1807.Scer\UAS.T:Ivir\HA1 under the control of Scer\GAL4sns.PK restores fusion in mbcD11.2 embryos and a wild-type somatic muscle pattern is formed.
Myoblast fusion remains severely impaired in mbcD11.2 embryos expressing mbcScer\UAS.T:Ivir\HA1 under the control of Scer\GAL4kirre-rP298. These embryos show a roughly twofold increase in muscle precursor formation (where a single fusion event between a founder cell and a fusion competent myoblast has occurred) compared to mbcD11.2 embryos.
Expression of mbcScer\UAS.T:Ivir\HA1 rescues the myoblast fusion defect in mbcD11.2 embryos when expressed using Scer\GAL4twi.PG or Scer\GAL4how-24B but not Scer\GAL4kirre-rP298.
Scer\GAL4twi.PG-mediated expression of mbcSH3W47K.Scer\UAS.T:Ivir\HA1 fails to rescue the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG-mediated expression of mbcDockerF6.4.Scer\UAS.T:Ivir\HA1 fails to rescue the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG- or Scer\GAL4how-24B-mediated expression of mbcCBS.Scer\UAS rescues the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG- or Scer\GAL4how-24B-mediated expression of mbcΔ1807.Scer\UAS.T:Ivir\HA1 rescues the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG- or Scer\GAL4how-24B-mediated expression of mbcNPxxP.Scer\UAS.T:Ivir\HA1 rescues the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG- or Scer\GAL4how-24B-mediated expression of mbcNPxxP.Δ1807.Scer\UAS.T:Ivir\HA1 rescues the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG- or Scer\GAL4how-24B-mediated expression of mbcΔPRM.Scer\UAS.T:Ivir\HA1 rescues the mbcD11.2 myoblast fusion defect.
Scer\GAL4twi.PG- or Scer\GAL4how-24B-mediated expression of mbcΔDHR1.Scer\UAS.T:Ivir\HA1 fails to rescue the mbcD11.2 myoblast fusion defect.