Clinical NeuroscienceLocalization of survival motor neuron protein in human apoptotic-like and regenerating muscle fibers, and neuromuscular junctionsBroccolini, Aldobrando1; Engel, W King1; Askanas, Valerie1,2Author Information 1USC Neuromuscular Center, Department of Neurology, University of Southern California School of Medicine, Good Samaritan Hospital, 637 South Lucas Avenue, Los Angeles, CA 90017-1912, USA 2Corresponding Author: Valerie Askanas ACKNOWLEDGEMENTS: Supported in part by grants from the National Institute of Health and the Muscular Dystrophy Association (to V.A.), and by the USC Neuromuscular Center Research Fund. A.B. is an Oschin Family Postdoctoral Fellow in Dr Askanas' laboratory. We are grateful to Dr G. Dreyfuss for his gift of 2B1 anti-SMN antibody. NOTE: A new example of ‘apoptosis-lente’ has been reported in myotonic dystrophy, in which there is strong TUNEL positivity in virtually all nuclei of both the very atrophic muscle fibers and, unlike chronic peripheral neuropathy, also in normal-size muscle fibers . Received 24 February 1999; accepted 26 March 1999 NeuroReport: June 3rd, 1999 - Volume 10 - Issue 8 - p 1637-1641 Buy Abstract MUTATIONS in the gene encoding survival motor neuron (SMN) protein are found in > 98% of patients with autosomal-recessive spinal muscular atrophy. We investigated the possible role of SMN in normal and abnormal human muscle by immunostaining biopsies of 20 patients with various neuromuscular diseases using monoclonal antibodies against SMN. SMN was strongly expressed cytoplasmically in chronic peripheral neuropathies, in about 80% of chronically denervated, very atrophic muscle fibers containing clumps of TUNEL-positive pyknotic nuclei: about 60% of those fibers also had cytoplasmic Bcl-2 and Bax immunoreactivity. In regenerating muscle fibers of various myopathies SMN co-localized with desmin, Bcl-2 and Bax; it was also present at the postsynaptic domain of normal human neuromuscular junctions. Thus, SMN may play a role in normal and pathological processes of adult human muscle fibers. © 1999 Lippincott Williams & Wilkins, Inc.