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Updated: Aug 14, 2026
Optical Cross-Sectional Muscle Area Determination of Drosophila Melanogaster Adult Indirect Flight Muscles
Published on: March 31, 2018
Drosophila calmodulin mutants with specific defects in the musculature or in the nervous system
Bo Wang1, Kathleen M C Sullivan, Kathy Beckingham
1Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA.
Abstract:
We have studied lethal mutations in the single calmodulin gene (Cam) of Drosophila to gain insight into the in vivo functions of this important calcium sensor. As a result of maternal calmodulin (CaM) in the mature egg, lethality is delayed until the postembryonic stages. Prior to death in the first larval instar, Cam nulls show a striking behavioral abnormality (spontaneous backward movement) whereas a mutation, Cam7, that results in a single amino acid change (V91G) produces a very different phenotype: short indented pupal cases and pupal death with head eversion defects. We show here that the null behavioral phenotype originates in the nervous system and involves a CaM function that requires calcium binding to all four sites of the protein. Further, backward movement can be induced in hypomorphic mutants by exposure to high light levels. In contrast, the V91G mutation specifically affects the musculature and causes abnormal calcium release in response to depolarization of the muscles. Genetic interaction studies suggest that failed regulation of the muscle calcium release channel, the ryanodine receptor, is the major defect underlying the Cam7 phenotype.
Insights
Lethal mutations in Drosophila calmodulin reveal distinct functions. Null mutations cause nervous system defects and backward movement, while a specific mutation affects muscle calcium release and ryanodine receptor regulation.
Area of Science:
- Molecular Biology
- Neuroscience
- Genetics
Background:
- Calmodulin (CaM) is a crucial calcium sensor protein.
- Studying lethal mutations in Drosophila's single calmodulin gene provides insights into its in vivo functions.
- Maternal CaM in eggs delays lethality until postembryonic stages.
Purpose of the Study:
- To investigate the in vivo functions of calmodulin in Drosophila.
- To characterize the distinct phenotypes associated with different calmodulin mutations.
- To elucidate the molecular mechanisms underlying calmodulin's roles in the nervous system and musculature.
Main Methods:
- Analysis of lethal calmodulin mutations in Drosophila.
- Phenotypic characterization of null and specific point mutations (Cam7 V91G).
- Genetic interaction studies, including analysis of ryanodine receptor interactions.
Main Results:
- Cam null mutants exhibit behavioral abnormalities (spontaneous backward movement) originating in the nervous system, requiring CaM calcium binding to all four sites.
- The Cam7 (V91G) mutation specifically affects muscle function, leading to abnormal calcium release and pupal defects.
- Backward movement in hypomorphic mutants can be induced by high light levels.
- Genetic interactions suggest failed regulation of the ryanodine receptor underlies the Cam7 phenotype.
Conclusions:
- Calmodulin plays distinct, essential roles in both Drosophila nervous system function and muscle calcium regulation.
- The V91G mutation highlights a specific role for CaM in regulating the muscle ryanodine receptor.
- Understanding these calmodulin functions is critical for comprehending calcium signaling pathways in vivo.
