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Mutants with delayed cell death of the ptilinal head muscles in Drosophila
1Division of Behaviour and Neurobiology, National Institute for Basic Biology, Okazaki, Japan.
Abstract:
The emergence of adult Drosophila melanogaster from the puparium is followed by the programmed degeneration of a number of muscle groups. We have isolated two X-linked mutants that delay the programmed death of at least some of these muscles. During eclosion, the fly makes use of a membranous sac, the ptilinum, which is later retracted into the head capsule. Six of the eight sets of muscles involved in the retraction then undergo degeneration. The muscle fibers initially show a gradual atrophy and then degenerate rapidly through fragmentation followed by absorption. In wild-type flies, this degeneration is obvious by 12 h after eclosion due to the loss of the birefringence of the muscles. Through mutagenesis with ethyl methanesulfonate, we isolated four mutants whose birefringence of the doomed muscles was retained even at 12 h. Mutants were genetically classified into two complementation groups; mcd-1 and mcd-2 (mcd: muscle cell death). The muscles of the mcd-1 mutants degenerate more slowly than that of the wild-type flies; the fibers enter the fragmentation step but are then not rapidly absorbed. In the mcd-2 mutants, the fibers atrophy more slowly than that in the wild-type flies and fail to undergo fragmentation. The difference in the process of the muscle death between the mcd-1 and the mcd-2 mutants suggests that at least two genes act on different steps in the process of muscle cell death.
Insights
Two X-linked Drosophila mutants, mcd-1 and mcd-2, were identified that delay programmed muscle cell death after eclosion. These mutants reveal distinct steps in muscle degeneration, impacting atrophy and fragmentation processes.
Area of Science:
- Developmental Biology
- Genetics
- Cell Biology
Background:
- Adult Drosophila melanogaster undergo programmed muscle degeneration after emerging from the puparium.
- Specific muscles involved in ptilinum retraction degenerate rapidly post-eclosion.
Purpose of the Study:
- To identify genetic factors influencing programmed muscle cell death in Drosophila.
- To characterize mutations that delay muscle degeneration during the post-eclosion period.
Main Methods:
- Ethyl methanesulfonate mutagenesis was used to generate mutants.
- X-linked mutants were isolated based on delayed muscle degeneration (retained birefringence at 12h post-eclosion).
- Genetic complementation tests classified mutants into two groups: mcd-1 and mcd-2.
Main Results:
- Four mutants were isolated, showing delayed muscle degeneration.
- mcd-1 mutants exhibited slower fragmentation and absorption of muscle fibers.
- mcd-2 mutants displayed slower atrophy and failed to fragment muscle fibers.
Conclusions:
- At least two distinct genes (mcd-1 and mcd-2) regulate different stages of programmed muscle cell death.
- These findings provide insights into the molecular mechanisms controlling muscle degeneration in Drosophila.
