Methylation of the Hprt gene on the inactive X occurs after chromosome inactivation - PubMed (original) (raw)

Methylation of the Hprt gene on the inactive X occurs after chromosome inactivation

L F Lock et al. Cell. 1987.

Abstract

DNA sequences have previously been identified in the first intron of the mouse Hprt gene that are methylated on the inactive but not the active X chromosome. The temporal relationship between methylation of these sequences and X-inactivation was studied in teratocarcinoma cells and postimplantation mouse embryos: the sequences are unmethylated prior to X-inactivation and do not become methylated on the inactive X in most fetal cells until several days postinactivation. Such inactive X-specific methylation occurs in a significantly smaller proportion of the cells in the extra-embryonic tissues, yolk sac mesoderm and endoderm, than in the fetus. These data suggest that the inactive X-specific methylation of sequences such as those in the first intron of the Hprt gene does not play any role in the primary events of X-inactivation, but may function as part of a secondary, tissue-specific mechanism for maintaining the inactive state.

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