Human Molecular Genetics Advance Access originally published online on January 11, 2006
Human Molecular Genetics 2006 15(4):581-587; doi:10.1093/hmg/ddi474
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Histone acetylation dependent allelic expression imbalance of BAPX1 in patients with the oculo-auriculo-vertebral spectrum
Institut für Humangenetik, Universitätsklinikum Essen, 45122 Essen, Germany
* To whom correspondence should be addressed. Tel: +49 2017234560; Fax: +49 2017235900; Email: b.horsthemke{at}uni-essen.de
The oculo-auriculo-vertebral spectrum (OAVS) (OMIM %164210) is a common developmental disorder characterized by hemifacial microsomia, epibulbar tumours, ear malformation and vertebral anomalies. Although rare familial cases suggest that OAVS has a genetic basis, no genetic defect has been identified so far. In a patient with OAVS and a chromosomal translocation t(4;8) we have found that the chromosome 4 breakpoint is 76.4 kb distal to the BAPX1 gene, which plays an essential role in craniofacial development. We did not detect any BAPX1 mutation in 105 patients, but observed a strong allelic expression imbalance (sAEI) in fibroblasts from five of 12 patients, but not in nine normal controls (Fisher's exact test, P=0.038). sAEI was de novo in one patient and inherited in two other patients. Prolonged cell culture or treatment with the histone deacetylase inhibitor Trichostatin A led to reactivation of the downregulated allele. We propose that epigenetic dysregulation of BAPX1 plays an important role in OAVS.