The deletion of the chromatin-remodelling protein Lsh in mice causes loss of DNA methylation – a process thought to be responsible for the expression of certain genes in a heritable, parent-specific manner. These so-called imprinted genes are associated with differentially methylated regions (DMRs) that are established during gametocyte development and maintained through embryogenesis. On p. 635, Fan and colleagues now examine whether loss of Lsh also affects imprinting. They report that in Lsh-null mouse embryos, imprinting is maintained at all loci examined, except at the cell cycle inhibitor Cdkn1c gene. Reactivated expression of the paternal copy of Cdkn1c correlates with a loss of methylation at a DMR in its promoter, where the authors show Lsh binds in vitro. These findings suggest that although Lsh is not required for the genome-wide maintenance of imprinting, it may be required for the de novo methylation of specific sites.

©2005.
2005