loh1/lohMB05750 mutant third instar larvae show a strong detachment of pericardial cells from the heart tube.
lohMB05750/lohMI02765 mutant third instar larvae show a strong detachment of pericardial cells from the heart tube.
During the development of lohMB05750/Df(2L)Exel7048 mutant larvae the pericardial cells irreversibly detach from the heart tube with the phenotype becoming fully visible at the third instar larval stage. Adult viability is not affected and the defect can also be detected in pharate adults. There is no effect on fertility. Determination and migration of heart precursor cells is unaffected. The detachment of the pericardial cells also ruptures the connection between the alary muscles and cardiomyocytes. Furthermore, the morphology of the cardiomyocytes itself is dramatically altered in lohMB05750/Df(2L)Exel7048 mutants, with the cells exhibiting an uncoordinated distribution of actin fibers and an altered cell shape.
The beating pattern of the heart is dramatically altered in lohMB05750/Df(2L)Exel7048 mutant third instar larvae. A changed contraction movement of the whole organ is observed along the posterior-anterior axis. In addition, no systole or diastole are detectable.
Homozygous lohMB05750 mutant third instar larvae exhibit severe defects in heart function. In contrast to wild type flies, lohMB05750 mutant flies fail to accumulate dye in the head after after injection of a fluorescent tracer into the abdomen.
The average lifespan of homozygous lohMB05750 mutant flies is decreased by 26% compared to controls.
As in wild type, the cardiomyocytes in lohMB05750 mutant embryos are localised along the dorsal midline at the end of embryogenesis (stage 17), showing that dorsal closure is unaffected. The luminal and basal membranes of the cardiomyocytes are covered by a distinct basement membrane and this is not significantly altered in lohMB05750 mutants. Although the pericardial cells are not fully detached from the embryonic heart, but small gaps are seen between the cells and rupture of the connecting ECM is detectable.
