Increased skewing of X chromosome inactivation with age in both blood and buccal cells.

The X chromosome inactivation pattern in peripheral blood cells becomes more skewed after age 55, and a genetic effect on this age-related skewing has been reported. We investigated the effect of age on X inactivation phenotype in blood, buccal cells and tissue from duodenal biopsies in 80 females aged 19-90 years. The X inactivation pattern correlated positively with age in blood (r = 0.238, P = 0.034) and buccal cells (r = 0.260, P = 0.02). The mean degree of skewing was higher in the elderly (>/=55 years) than in the young (<55 years) in blood (70.1 and 63.5%, respectively, P = 0.013) and in buccal cells (64.7 and 59.0%, respectively, P = 0.004). Correlation of X inactivation between the different tissues was high in all tissues with a tendency to increase with age for blood and buccal cells (P = 0.082). None of the duodenal biopsies had a skewed X inactivation, and the mean degree of skewing was similar in the two age groups. The tendency for the same X chromosome to be the preferentially active X in both blood and buccal cells with advancing age is in agreement with a genetic effect on age-related skewing and indicates that genes other than those involved in hematopoiesis should be investigated in the search for genes contributing to age related skewing. Copyright 2007 S. Karger AG, Basel.