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J Med Genet 2009;46:856-861 doi:10.1136/jmg.2009.067892
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Segregation of enlarged vestibular aqueducts in families with non-diagnostic SLC26A4 genotypes

  1. B Y Choi1,
  2. A C Madeo2,
  3. K A King2,
  4. C K Zalewski2,
  5. S P Pryor2,
  6. J A Muskett2,
  7. W E Nance3,
  8. J A Butman4,
  9. C C Brewer2,
  10. A J Griffith2
  1. 1
    Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, Maryland, USA
  2. 2
    Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, Maryland, USA
  3. 3
    Department of Human Genetics, Medical College of Virginia, Richmond, Virginia, USA
  4. 4
    Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland, USA
  1. Correspondence to Dr A J Griffith, NIDCD/NIH, 5 Research Court, Room 1A-13D, Rockville, MD 20850, USA; griffita{at}nidcd.nih.gov
  • Received 19 March 2009
  • Revised 22 May 2009
  • Accepted 25 May 2009
  • Published Online First 2 July 2009

Abstract

Background: Hearing loss with enlarged vestibular aqueduct (EVA) can be inherited as an autosomal recessive trait caused by bi-allelic mutations of SLC26A4. However, many EVA patients have non-diagnostic SLC26A4 genotypes with only one or no detectable mutant alleles.

Methods and results: In this study, the authors were unable to detect occult SLC26A4 mutations in EVA patients with non-diagnostic genotypes by custom comparative genomic hybridisation (CGH) microarray analysis or by sequence analysis of conserved non-coding regions. The authors sought to compare the segregation of EVA among 71 families with two (M2), one (M1) or no (M0) detectable mutant alleles of SLC26A4. The segregation ratios of EVA in the M1 and M2 groups were similar, but the segregation ratio for M1 was significantly higher than in the M0 group. Haplotype analyses of SLC26A4-linked STR markers in M0 and M1 families revealed discordant segregation of EVA with these markers in eight of 24 M0 families.

Conclusion: The results support the hypothesis of a second, undetected SLC26A4 mutation that accounts for EVA in the M1 patients, in contrast to non-genetic factors, complex inheritance, or aetiologic heterogeneity in the M0 group of patients. These results will be helpful for counselling EVA families with non-diagnostic SLC26A4 genotypes.

Footnotes

  • Additional tables are published online only at http://jmg.bmj.com/content/vol46/issue12

  • Funding This work was supported by NIH intramural research funds Z01-DC-000039, Z01-DC-000060 and Z01-DC-000064 and the Intramural Research Program of the National Human Genome Research Institute.

  • Competing interests None.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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