Evidence that mutations in the X-linked DDP gene cause incompletely penetrant and variable skewed X inactivation.


Journal Article

X chromosome inactivation results in the random transcriptional silencing of one of the two X chromosomes early in female development. After random inactivation, certain deleterious X-linked mutations can create a selective disadvantage for cells in which the mutation is on the active X chromosome, leading to X inactivation patterns with the mutation on the inactive X chromosome in nearly 100% of the individual's cells. In contrast to the homogeneous patterns of complete skewed inactivation noted for many X-linked disorders, here we describe a family segregating a mutation in the dystonia-deafness peptide (DDP) gene, in which female carriers show incompletely penetrant and variable X inactivation patterns in peripheral blood leukocytes, ranging between 50:50 and >95:5. To address the genetic basis for the unusual pattern of skewing in this family, we first mapped the locus responsible for the variable skewing to the proximal long arm (Xq12-q22) of the X chromosome (Z=5. 7, P=.002, LOD score 3.57), a region that includes both the DDP and the XIST genes. Examination of multiple cell types from women carrying a DDP mutation and of peripheral blood leukocytes from women from two unrelated families who carry different mutations in the DDP gene suggests that the skewed X inactivation is the result of selection against cells containing the mutant DDP gene on the active X chromosome, although skewing is apparently not as severe as that seen for many other deleterious X-linked mutations. Thus, DDP is an example of an X-linked gene for which mutations cause partial cell selection and thus incompletely skewed X inactivation in peripheral blood leukocytes.

Full Text

Cited Authors

  • Plenge, RM; Tranebjaerg, L; Jensen, PK; Schwartz, C; Willard, HF

Published Date

  • March 1999

Published In

Volume / Issue

  • 64 / 3

Start / End Page

  • 759 - 767

PubMed ID

  • 10053010

Pubmed Central ID

  • 10053010

Electronic International Standard Serial Number (EISSN)

  • 1537-6605

International Standard Serial Number (ISSN)

  • 0002-9297

Digital Object Identifier (DOI)

  • 10.1086/302286


  • eng