Suicide muscle cell programme-apoptosis. Ultrastructural study.

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.