Imprinting.

Abstract

Over 3000 years ago, mule breeders had already observed parent-specific effects in the offspring of crossbred horses and donkeys. A mare crossed with a donkey yields a mule, whereas a stallion crossed with a donkey yields a hinny, which has stronger legs and shorter ears than a mule. The parent-of-origin effects point to different functions for maternal and paternal genomes. This is due to a process now generally known as genomic imprinting. Despite these early clues, it was not until the early 1980’s before the phenomenon of genomic imprinting was discovered. Pronuclear transplantation studies in mice showed that gynogenetic embryos with two maternal genomes and androgenetic embryos with two paternal genomes were arrested early in development. The gynogenetic embryos showed a relatively normal embryo but poor extraembryonic growth whereas there were mainly extraembryonic tissues and poor embryonic development in the androgenetic embryos. These experiments demonstrated that certain genes are preferentially expressed from only one parental genome and that both paternal and maternal genomes are required for normal embryonic development (McGrath and Solter, 1984; Barton et al 1984).KeywordsImprint GenePaternal AlleleMaternal AlleleCTCF BindingPaternal GenomeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.