The Biology of Genomic Imprinting
Herry Herman and Robert Feil
from: Epigenetics (Edited by: Jörg Tost). Caister Academic Press, U.K. (2008)
'Genomic imprinting' refers to the epigenetic marking of the parental origin of certain chromosomal domains (i.e., depending whether they are inherited from the mother or the father). It takes place at a small subset of genes termed imprinted genes, where the epigenetic marking dictates parental allele-specific (imprinted) gene expression in somatic tissues. These marks take form as differential DNA methylation, at specialized sequence elements called 'imprinting control regions' (ICRs). Translating these methylation imprints into the appropriate patterns of gene expression is crucial for the development and growth of the embryo, and for postnatal well-being. This review focuses on the biology of genomic imprinting in mammals, discussed in two parts. The first part elaborates the 'reading' of the imprints; i.e., how tissues decode the imprints into imprinted expression. Included is a discussion on the related process, which assures the maintenance of these imprints in somatic tissues. Examples of various reading mechanisms are presented including the blocking of long-range promoter-enhancer interactions and the involvement of non-coding RNAs in chromatin repression. The second part addresses the mechanism involved in assuring the re-establishment of new imprints in the next generation. It discusses the processes which erase and re-establish the imprints in the male and female germ lines read more ...