Ultrastructural analysis and TUNEL demonstrate motor neuron apoptosis in Werdnig-Hoffmann disease

Werdnig-Hoffmann disease (WHD) is the most severe clinical type of spinal m uscular atrophy characterized by loss of lower motor neurons and paralysis. We examined the hypothesis that disease pathogenesis is based on an inappr opriate persistence of normally occurring motor neuron programmed cell deat h. The diagnosis of WHD was made on the basis of clinical findings, electro myoneurography, and biopsy, and further confirmed by mutation analysis of t he survival motor neuron (SMN) and neuronal apoptosis inhibitory protein (N AIP) genes using PCR. We used ultrastructural analysis as well as TUNEL and ISEL methods to assess DNA fragmentation, and immunocytochemistry to ident ify expression of the apoptosis-related proteins bcl-2 and p53. A significa nt number of motor neurons in the spinal cord of children with WHD were sho wn to die by apoptosis. As revealed by TUNEL, dying neurons in WHD patients comprised 0.2%-6.4% of the neuron numbers counted. This finding contradict s earlier studies that failed to find such evidence and suggests that early blockade of prolonged meter neuron apoptosis may be a potential therapeuti c strategy for WHD.