title: Nuclear reprogramming of cloned embryos and its implications for therapeutic cloning.
abstract: Therapeutic cloning, whereby somatic cell nuclear transfer (SCNT) is used to generate patient-specific embryonic stem cells (ESCs) from blastocysts cloned by nuclear transfer (ntESCs), holds great promise for the treatment of many human diseases. ntESCs have been derived in mice and cattle, but thus far there are no credible reports of human ntESCs. Here we review the recent literature on nuclear reprogramming by SCNT, including studies of gene expression, DNA methylation, chromatin remodeling, genomic imprinting and X chromosome inactivation. Reprogramming of genes expressed in the inner cell mass, from which ntESCs are derived, seems to be highly efficient. Defects in the extraembryonic lineage are probably the major cause of the low success rate of reproductive cloning but are not expected to affect the derivation of ntESCs. We remain optimistic that human therapeutic cloning is achievable and that the derivation of patient-specific ntESC lines will have great potential for regenerative medicine.
authors.affiliation: Center for Regenerative Biology and Department of Animal Science, University of Connecticut, Storrs, Connecticut 06269, USA. xiangzhong.yang@uconn.edu
authors.forename: Xiangzhong
authors.initials: X
authors.lastname: Yang
authors.forename: Sadie L
authors.initials: SL
authors.lastname: Smith
authors.forename: X Cindy
authors.initials: XC
authors.lastname: Tian
authors.forename: Harris A
authors.initials: HA
authors.lastname: Lewin
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Renard
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Wakayama
mesh_terms: D000818:Animals; D002417:Cattle; D065150:Cellular Reprogramming; D019976:Cloning, Organism; D004622:Embryo, Mammalian / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000378:metabolism; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D051379:Mice; D008954:Models, Biological; D053652:Nuclear Transfer Techniques