title: Mammalian genomic imprinting.
abstract: Normal mammalian development requires a maternal and paternal contribution, which is attributed to imprinted genes, or genes that are expressed from a single parental allele. Approximately 100 imprinted genes have been reported in mammals thus far. Imprinted genes are controlled by cis-acting regulatory elements, termed imprinting control regions (ICRs), which have parental-specific epigenetic modifications, including DNA methylation. ICRs are methylated by de novo DNA methyltransferases during germline development; these parental-specific modifications must be maintained following fertilization when the genome is extensively reprogrammed. Many imprinted genes reside in ∼1-megabase clusters, with two major mechanisms of imprinting regulation currently recognized, CTCF-dependent insulators and long noncoding RNAs. Unclustered imprinted genes are generally regulated by germline-derived differential promoter methylation. Here, we describe the identification and functions of imprinted genes, cis-acting control sequences, trans-acting factors, and imprinting mechanisms in clusters. Finally, we define questions that require more extensive research.
authors.affiliation: Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19063, USA. bartolom@mail.med.upenn.edu
authors.forename: Marisa S
authors.initials: MS
authors.lastname: Bartolomei
authors.forename: Anne C
authors.initials: AC
authors.lastname: Ferguson-Smith
mesh_terms: D000818:Animals; D019175:DNA Methylation; D005260:Female; D018507:Gene Expression Regulation, Developmental; D030342:Genetic Diseases, Inborn / Q000235:genetics; D018392:Genomic Imprinting; D006801:Humans; D008297:Male; D008322:Mammals / Q000235:genetics* / Q000254:growth & development; D051379:Mice; D008957:Models, Genetic; D022661:RNA, Untranslated / Q000502:physiology
chemical_list: D022661:RNA, Untranslated