Phenotypic expression of maternally inherited deafness is affected by RNA modification and cytoplasmic ribosomal proteins

Mol Genet Metab. 2009 Aug;97(4):297-304. doi: 10.1016/j.ymgme.2009.05.003. Epub 2009 May 13.

Abstract

The homoplasmic mitochondrial A1555G mutation in the 12S rRNA gene leads to a mitochondrial translation disorder associated with deafness. The absence of disease in non-cochlear tissues in all patients, and in the cochlea in some patients, is not well understood. We used a system-based approach, including whole genome expression and biological function analysis, to elucidate the pathways underlying tissue specificity and clinical severity of this condition. Levels of over 48K RNA transcripts from EBV-transformed lymphoblasts of deaf and hearing individuals with the A1555G mutation and controls were obtained. Differentially expressed transcripts were functionally grouped using gene set enrichment analysis. Over 50 RNA binding proteins were differentially expressed between deaf and hearing individuals with the A1555G mutation (P-value of 2.56E-7), confirming previous genetic data implicating this pathway in the determination of the severity of hearing loss. Unexpectedly, the majority of cytoplasmic ribosomal genes were up-regulated in a coordinated fashion in individuals with the A1555G mutation versus controls (P-value of 3.91E-135). This finding was verified through real time RT-PCR, and through measuring of protein levels by flow cytometry. Analysis of expression levels of other differentially expressed genes suggests that this coordinated over-expression of cytoplasmic ribosomal proteins might occur through the Myc/Max pathway. We propose that expression levels of RNA binding proteins help determine the severity of the cochlear phenotype, and that coordinated up-regulation of the cytoplasmic translation apparatus operates as a compensation mechanism in unaffected tissues of patients with maternal deafness associated with the A1555G mutation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Deafness / genetics*
  • Female
  • Gene Expression Profiling
  • Hearing Loss / genetics*
  • Humans
  • Oligonucleotide Array Sequence Analysis
  • Phenotype
  • RNA / genetics
  • RNA / metabolism
  • RNA, Mitochondrial
  • RNA, Ribosomal / genetics*
  • RNA-Binding Proteins / genetics
  • Ribosomal Proteins / genetics*
  • Ribosomal Proteins / metabolism

Substances

  • RNA, Mitochondrial
  • RNA, Ribosomal
  • RNA, ribosomal, 12S
  • RNA-Binding Proteins
  • Ribosomal Proteins
  • RNA