blow2 mutant embryos display defects in the migration and morphology of visceral longitudinal muscle founder cells as well as the muscle fusion.
blow1/blow2 transheterozygote embryos display defects in the migration and morphology of visceral longitudinal muscle founder cells as well as the muscle fusion.
blow2 embryos show rare myoblast fusion events up to the binucleate precursor stage.
The extent of myoblast fusion in blow2 mutant embryos is significantly reduced compared to wild type.
By stage 14 in blow2 mutant embryos, mini-muscles with 3-4 nuclei are apparent at the site of the developing DA1 and DO1 muscles, but further fusion fails to occur. (By contrast stage 15-16 wild type DA1 contains up to 14 nuclei). Founder (precursor) muscle cells form normally in these embryos.
Myoblasts fail to fuse and form clusters of teardrop-shaped cells in roughly the locations corresponding to the ventral, lateral and dorsal muscle groups. At stage 13 normal numbers of prefusion complexes are present and there is no change in morphology or number of paired vesicles in the complexes. By stage 14 myoblasts have sorted into groups of teardrop-shaped cells that share attachment sites on a single pioneer cell, giving a 'bunch of grapes' morphology. Most unfused cells are cleared by macrophages by the end of stage 16.
Myoblasts fail during fusion to form myotubes.
blow2 has fusion competent cell phenotype, enhanceable by Df(3L)BK9
blow2 has embryonic/larval somatic muscle cell phenotype, non-enhanceable by HemG1-37
blow2 has somatic muscle primordium phenotype, non-enhanceable by HemG1-37
blow2 has embryonic/larval somatic muscle cell phenotype, suppressible by Scer\GAL4twi.PG/HemUAS.cHa
blow2 has somatic muscle primordium phenotype, suppressible by Scer\GAL4twi.PG/HemUAS.cHa
blow2 is an enhancer of fusion competent cell phenotype of sizT1032
blow[+]/blow2 is an enhancer of embryonic/larval somatic muscle cell phenotype of HemG1-37
blow[+]/blow2 is an enhancer of somatic muscle primordium phenotype of HemG1-37
Myoblast fusion is significantly compromised in blow2; Df(3L)BK9 double mutants. There is a greater percentage of hemisegments with a reduced number of nuclei in the double mutants than there is in the single mutants.
Myoblast fusion is significantly compromised in blow2; sizT1032 double mutants. There is a greater percentage of hemisegments with a reduced number of nuclei in the double mutants than there is in the single mutants.
The reduction of myoblast fusion seen in stage 15 HemG1-37/HemG1-37 embryos is enhanced by blow2/+. The muscle fusion phenotype of double homozygous blow2; HemG1-37 embryos resembles that of blow2 homozygotes rather than HemG1-37 homozygotes. HemScer\UAS.cHa; Scer\GAL4twi.PG partially suppresses the loss of muscle fusion seen in blow2 homozygous embryos. The resulting embryos form fused and attached muscles, although defects in muscle number, size and attachment occur.
