- Neurology www.neurology.org doi: 10.1212/WNL.52.9.1905 Neurology June 1, 1999 vol. 52 no. 9 1905 Ser(UCN) C.M. Sue , MD, PhD, K. Tanji , MD, PhD, G. Hadjigeorgiou , MD, PhD, A.L. Andreu , MD, I. Nishino , MD, PhD, S. Krishna , PhD, C. Bruno , MD, M. Hirano , MD, S. Shanske , PhD, E. Bonilla , MD, N. Fischel-Ghodsian , MD, S. DiMauro , MD and R. Friedman , MD, PhD Author Affiliations From the Departments of Neurology (Drs. SueTanji, Hadjigeorgiou, Andreu, Nishino, Krishna, Bruno, Hirano, Shanske, Bonilla, and DiMauro) and Pathology (Dr. Bonilla), Columbia University College of Physicians and Surgeons, New York, NY; Centre d’Investigacions en Bioquimica i Biologia Molecular (Dr. Andreu), Hospitals Vall d’Hebron, Barcelona, Spain; Department of Pediatrics (Dr. Fischel-Ghodsian), Steven Spielberg Pediatric Research Center, Cedars-Sinai Medical Center; and The House Ear Clinic and House Ear Institute (Dr. Friedman), Los Angeles, CA. Address correspondence and reprint requests to Dr. S. DiMauro, 4-420 College of Physicians and Surgeons, 630 West 168th Street, New York, NY 10032. ABSTRACT Article abstract Thirty-six of 43 maternally related members of a large African American family experienced hearing loss. A muscle biopsy specimen from the proband showed cytochrome c oxidase (COX)-deficient fibers but no ragged-red fibers; biochemical analysis showed marked reduction of COX activity. A novel T7511C point mutation in the tRNA Ser(UCN) gene was present in almost homoplasmic levels (>95%) in the blood of 18 of 20 family members, and was also found in lower abundance in the other two. Single-fiber PCR showed that the mutational load was greater in COX-deficient muscle fibers. The tRNA Ser(UCN) gene may be a “hot spot” for mutations associated with maternally transmitted hearing loss. Sensorineural hearing loss (SNHL) is a common clinical manifestation in patients with mitochondrial disorders. Although SNHL in the context of multisystemic syndromes has been associated with numerous mtDNA point mutations and rearrangements, isolated SNHL has been associated with only three mutations: A1555G, 1 A7445G, 2 and 7472ins. 3 The aim of this study was to identify the mtDNA mutation in a large family with maternally transmitted SNHL. Ma㼠㼑㼞㼚a㼘㼘y 㼕㼚㼔㼑㼞㼕㼠㼑㼐 㼔㼑a㼞㼕㼚㼓 㼘㼛㼟㼟 㼕㼚 a 㼘a㼞㼓㼑 㼗㼕㼚㼐㼞㼑㼐 㼣㼕㼠㼔 a 㼚㼛㼢㼑㼘 T㻣㻡㻚㻚㻚 㼔㼠㼠㼜㻦㻛㻛㼣㼣㼣㻚㼚㼑㼡㼞㼛㼘㼛㼓y㻚㼛㼞㼓㻛㼏㼛㼚㼠㼑㼚㼠㻛㻡㻞㻛㻥㻛㻝㻥㻜㻡㻚㼒㼡㼘㼘 㻝 㼛㼒 㻥 㻞㻜㻝㻞㻛㻜㻤㻛㻜㻤 㻝㻝㻦㻟㻡