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Suicide muscle cell programme-apoptosis. Ultrastructural study
1Department of Neurology, Medical Academy and Neuromuscular Unit, Medical Research Centre, Polish Academy of Sciences, Warszawa.
Abstract:
To establish the ultrastructural criteria of suicide muscle cell programme-apoptosis we investigated the muscle biopsies of acute fatal spinal muscular atrophy (SMA) infants with gene survival motor neurone (SMN) exon 7 deletion. The muscle cell apoptosis was characterised by precisely sequential morphology of both cell nucleus and sarcoplasm. The most characteristic feature was the aggregation of nuclear chromatin initially into peripherally located ring and later into uniformly dense, dark masses. Accompanying features included sarcoplasmic condensation cell shrinking and fragmentation into multiple bodies. The coexistence of muscle cells at different stages of apoptosis in the same tissue section was the most prominent and specific feature of suicide muscle cell programme. The appearance of an identical sequence of ultrastructural changes in muscle as observed in other tissues suggests that a unique mechanism is involved in genetically programmed cell death.
Insights
Spinal muscular atrophy (SMA) involves a programmed cell death (apoptosis) in muscle cells, characterized by specific nuclear and cytoplasmic changes. This genetically programmed cell death mechanism in SMA muscle cells offers new insights into apoptosis.
Area of Science:
- Cell Biology
- Genetics
- Neurology
Background:
- Spinal muscular atrophy (SMA) is a severe genetic neuromuscular disorder.
- Understanding the cellular mechanisms of muscle degeneration in SMA is crucial.
Purpose of the Study:
- To define the ultrastructural characteristics of apoptosis in muscle cells of infants with SMA.
- To identify specific morphological changes indicative of programmed cell death in SMA.
Main Methods:
- Investigation of muscle biopsies from infants with acute fatal SMA.
- Detailed ultrastructural analysis using electron microscopy.
Main Results:
- Muscle cell apoptosis in SMA exhibited sequential nuclear and sarcoplasmic changes.
- Key features included chromatin aggregation into dense masses and cell fragmentation.
- Coexistence of various apoptosis stages within the same tissue section was a specific finding.
Conclusions:
- Identified distinct ultrastructural criteria for apoptosis in SMA muscle cells.
- The findings suggest a genetically programmed cell death mechanism in SMA.
- The observed sequence of changes may indicate a conserved apoptosis pathway.