A novel MT-CO1 m.6498C>A variation associated with the m.7444G>A mutation in the mitochondrial COI/tRNA(Ser(UCN)) genes in a patient with hearing impairment, diabetes and congenital visual loss

Research output: Contribution to journalArticle


Mitochondrial diseases are a clinically heterogeneous group of disorders that arise as a result of dysfunction of the mitochondrial respiratory chain. Sensorineural hearing loss (SNHL) has been described in association to different mitochondrial multisystem syndromes, often involving the central nervous system, neuromuscular, or endocrine organs. In this study, we described a Tunisian young girl with hearing impairment, congenital visual loss and maternally inherited diabetes. No mutation was found in the mitochondrial tRNA(Leu(UUR)) and the 12S rRNA genes. However, we detected the m.7444G>A mutation in the mitochondrial COI/tRNA(Ser(UCN)) genes. This mutation eliminates the termination codon of the MT-CO1 gene and extends the COI polypeptide by three amino acids (Lys-Gln-Lys) to the C-terminal. The whole mitochondrial genome screening revealed the presence of a novel mutation m.6498C>A (L199I) in the mitochondrial DNA-encoded subunit I of the cytochrome c oxidase (COX). This "probably damaging" transversion affects a highly conserved domain and it was absent in 200 Tunisian controls. The studied patient was classified under the haplogroup H2a.


  • Emna Mkaouar-Rebai
  • Imen Chamkha
  • Thouraya Kammoun
  • Olfa Alila-Fersi
  • Hajer Aloulou
  • Mongia Hachicha
  • Faiza Fakhfakh
External organisations
  • University of Sfax
Research areas and keywords


  • Adolescent, Amino Acid Sequence, Codon, Terminator, Deaf-Blind Disorders, Diabetes Mellitus, Electron Transport Complex IV, Female, Hearing Loss, Sensorineural, Humans, Mitochondrial Diseases, Molecular Sequence Data, Mutation, Protein Structure, Secondary, RNA, Transfer, Ser, Tunisia
Original languageEnglish
Pages (from-to)585-91
Number of pages7
JournalBiochemical and Biophysical Research Communications
Issue number2
Publication statusPublished - 2013 Jan 11
Publication categoryResearch
Externally publishedYes