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Deletion of exon 8 from the EXT1 gene causes multiple osteochondromas (MO) in a family with three affected members.

Authors: Zhuang, Lei  Gerber, Simon D  Kuchen, Stefan  Villiger, Peter M  Trueb, Beat 
Citation: Zhuang L, etal., Springerplus. 2016 Jan 22;5:71. doi: 10.1186/s40064-016-1695-6. eCollection 2016.
Pubmed: (View Article at PubMed) PMID:26839764
DOI: Full-text: DOI:10.1186/s40064-016-1695-6

Multiple osteochondromas (also called hereditary multiple exostoses) is an autosomal dominant disorder characterized by multiple cartilaginous tumors, which are caused by mutations in the genes for exostosin-1 (EXT1) and exostosin-2 (EXT2). The goal of this study was to elucidate the genetic alterations in a family with three affected members. Isolation of RNA from the patients' blood followed by reverse transcription and PCR amplification of selected fragments showed that the three patients lack a specific region of 90 bp from their EXT1 mRNA. This region corresponds to the sequence of exon 8 from the EXT1 gene. No splice site mutation was found around exon 8. However, long-range PCR amplification of the region from intron 7 to intron 8 indicated that the three patients contain a deletion of 4318 bp, which includes exon 8 and part of the flanking introns. There is evidence that the deletion was caused by non-homologous end joining because the breakpoints are not located within a repetitive element, but contain multiple copies of the deletion hotspot sequence TGRRKM. Exon 8 encodes part of the active site of the EXT1 enzyme, including the DXD signature of all UDP-sugar glycosyltransferases. It is conceivable that the mutant protein exerts a dominant negative effect on the activity of the EXT glycosyltransferase since it might interact with normal copies of the enzyme to form an inactive hetero-oligomeric complex. We suggest that sequencing of RNA might be superior to exome sequencing to detect short deletions of a single exon.

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CRRD Object Information
CRRD ID: 13208227
Created: 2017-08-08
Species: All species
Last Modified: 2017-08-08
Status: ACTIVE



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