An X-linked imprinted cluster defies the classical mechanisms of epigenetic regulation

Date of Completion

January 2008


Biology, Genetics




Genomic imprinting is characterized by allele-specific gene expression that is dependent on parental origin. The epigenetic hallmarks of imprinting are allele-specific methylation of cytosines within local CpG islands and/or the allele-specific production of non-coding RNAs. While the current understanding of imprinting biology centers solely on autosomal genes, mechanisms behind X-linked imprinting remain a black box. As a consequence of X-inactivation, genes on the X chromosome are subject to silencing epigenetic marks such as DNA methylation. Despite this, a newly discovered imprinting cluster has been identified on the Mus musculus X chromosome. In this study, the Xlr3b/4b/4c locus is scrutinized for the epigenetic marks closely associated with autosomal imprinted genes. This study offers the first investigation into genomic imprinting on the X-chromosome outside of the Xist locus. The findings presented also provide strong evidence for a novel imprinting mechanism via RNA processing. ^