Epigenetics and imprint resetting in cloned animals

Abstract

Mammalian somatic cell cloning is extremely inefficient, with most clones failing to develop past implantation. This is presumably caused by epigenetic errors as a result of inadequate reprogramming of a somatic cell nucleus to a zygotic role. Imprinted genes have been implicated in the demise of somatic cell clones. This review discusses the pros and cons of this assumption and considers aspects of imprinted gene expression and DNA methylation in somatic cell clones. In summary, imprinted genes may be most relevant as an indicator for reprogramming but are probably not more vulnerable to reprogramming errors than nonimprinted genes. In contrast, changes in the methylation state indicate that failure of clones is often associated with abnormal methylation of individual sequences as well as the genome as a whole.