title: Mutations in the two ribosomal RNA genes in mitochondrial DNA among Finnish children with hearing impairment.
abstract: BACKGROUND
  Mutations in the two MT-RNR genes in mitochondrial DNA can cause hearing impairment that presents with variable severity and age of onset. In order to study the prevalence of mutations in MT-RNR1 and MT-RNR2 genes among Finnish children, we studied a ten-year cohort of hearing impaired children born in Northern Finland.
  
  
  METHODS
  We studied children, who had been born in Northern Finland in 1993-2002 and who had been ascertained to have hearing impairment by 31 December 2007. Samples from 103 children were sequenced in order to find mutations in the MT-RNR1 and MT-RNR2 genes.
  
  
  RESULTS
  One child harboured the pathogenic m.1555A > G mutation in MT-RNR1 suggesting a frequency of 4.4/100,000 in the Finnish paediatric population. In addition, eight rare variants and 13 polymorphisms were found in MT-RNR1 and MT-RNR2 genes. Five of the rare variants were deemed to be haplogroup-specific polymorphisms rather than putative pathogenic mutations, while the remaining three variants have been reported in various haplogroups. Among them m.990 T > C occurs at a conserved site.
  
  
  CONCLUSIONS
  The presence of m.990 T > C variant in various haplogroups and the rather high degree of conservation at this site suggest that this transition is a pathogenic rather than homoplasic neutral variant. Identification of further patients with m.990 T > C and segregation analysis in their families should help in determining the pathogenic potential of this variant.
authors: Department of Otorhinolaryngology, Oulu University Hospital, Oulu, Finland. sanna.hakli@oulu.fi.|Medical Research Center, Oulu, Finland. sanna.hakli@oulu.fi.|Institute of Clinical Medicine, Department of Otorhinolaryngology, University of Oulu, Oulu, Finland. sanna.hakli@oulu.fi.|Department of Clinical Medicine, Otorhinolaryngology, University of Oulu, P.O. Box 5000, FIN-90014, Oulu, Finland. sanna.hakli@oulu.fi.
authors: Sanna
authors: S
authors: Häkli
authors: Department of Otorhinolaryngology, Oulu University Hospital, Oulu, Finland. mirjaluotonen@yahoo.com.
authors: Mirja
authors: M
authors: Luotonen
authors: Institute of Clinical Medicine, Department of Otorhinolaryngology, University of Oulu, Oulu, Finland. martti.sorri@oulu.fi.
authors: Martti
authors: M
authors: Sorri
authors: Medical Research Center, Oulu, Finland. kari.majamaa@oulu.fi.|Institute of Clinical Medicine, Department of Neurology, University of Oulu, Oulu, Finland. kari.majamaa@oulu.fi.|Department of Neurology, Oulu University Hospital, Oulu, Finland. kari.majamaa@oulu.fi.
authors: Kari
authors: K
authors: Majamaa
mesh_terms: D002648:Child; D002675:Child, Preschool; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D005387:Finland / Q000453:epidemiology; D020459:Genes, rRNA / Q000235:genetics*; D006239:Haplotypes; D034381:Hearing Loss / Q000453:epidemiology / Q000235:genetics*; D006801:Humans; D008297:Male; D009154:Mutation
chemical_list: D004272:DNA, Mitochondrial
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