live-imaging-and-analysis-of-muscle-contractions-in-drosophila-embryo

Live Imaging and Analysis of Muscle Contractions in <em>Drosophila</em> Embryo

Coordinated muscle contractions are a form of rhythmic behavior seen early during development in Drosophila embryos. Neuronal sensory feedback circuits ...

Texas A&M University

Genetic defects in protein O-mannosyltransferase 1 (POMT1) and POMT2 underlie severe muscular dystrophies.  genes are evolutionarily conserved in metazoan organisms. In , both male and female  mutants show a clockwise rotation of adult abdominal segments, suggesting a chirality of underlying pathogenic mechanisms. Here we described and analyzed a similar phenotype in  mutant embryos that shows left-handed body torsion. Our experiments demonstrated that coordinated muscle contraction waves are associated with asymmetric embryo rolling, unveiling a new chirality marker in  development. Using genetic and live-imaging approaches, we revealed that the torsion phenotype results from differential rolling and aberrant patterning of peristaltic waves of muscle contractions. Our results demonstrated that peripheral sensory neurons are required for normal contractions that prevent the accumulation of torsion. We found that  mutants show abnormal axonal connections of sensory neurons.  transgenic expression limited to sensory neurons significantly rescued the torsion phenotype, axonal connectivity defects, and abnormal contractions in  mutant embryos. Together, our data suggested that protein O-mannosylation is required for normal sensory feedback to control coordinated muscle contractions and body posture. This mechanism may shed light on analogous functions of  genes in mammals and help to elucidate the etiology of neurological defects in muscular dystrophies. Protein O-mannosyltransferases (POMTs) are evolutionarily conserved in metazoans. Mutations in  cause severe muscular dystrophies associated with pronounced neurological defects. However, neurological functions of POMTs remain poorly understood. We demonstrated that  mutations in  result in abnormal muscle contractions and cause embryo torsion. Our experiments uncovered a chirality of embryo movements and a unique -dependent mechanism that maintains symmetry of a developing system affected by chiral forces. Furthermore,  were found to be required for proper axon connectivity of sensory neurons, suggesting that O-mannosylation regulates the sensory feedback controlling muscle contractions. This novel POMT function in the peripheral nervous system may shed light on analogous functions in mammals and help to elucidate pathomechanisms of neurological abnormalities in muscular dystrophies.

Ishita Chandel

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