The X inactivation centre and X chromosome imprinting.

Genetic imprinting is an important component of X chromosome inactivation, since in marsupials and extraembryonic cell lineages of mice and rats, the paternally derived X chromosome is preferentially inactivated. This imprinting is thought to be mediated via the X inactivation centre. The gene symbolized Xist is a strong candidate for a role in the function of the X inactivation centre and the paper reviews the evidence that Xist shows imprinted behaviour and that differential methylation is the possible basis of the imprint. This paper is the text of the speech given by Dr. Mary Lyon after the awarding of the Mauro Baschirotto prize at the meeting of the European Society of Human Genetics in Paris, June 1994 (see page 305).