Reprogramming of epigenetic inheritance by somatic cell nuclear transfer.
Somatic cloning by nuclear transfer returns a differentiated cell to a totipotent stage, a process termed nuclear reprogramming. During this de-differentiation process, genes inactivated during tissue differentiation are re-activated in a temporal and spatial special manner. It is believed that tissue differentiation occurs through epigenetic mechanisms, genetic inheritance that does not involve changes in DNA sequences. Developmental abnormalities and a high mortality rate in cloned offspring have frequently been observed and probably result from incomplete nuclear reprogramming. In this review, the reprogramming of two epigenetic mechanisms, imprinting and X chromosome inactivation, as well as recent attempts to modify pre-existing epigenetic marks in donor cells to improve nuclear transfer efficacy, are discussed.
Tian
X Cindy
XC
Centre for Regenerative Biology/Department of Animal Science, University of Connecticut, Storrs, CT 06269-4243, USA. xtian@canr.uconn.edu
D000818:Animals; D002417:Cattle; D019976:Cloning, Organism; D004303:Dosage Compensation, Genetic; D044127:Epigenesis, Genetic / Q000502:physiology*; D005260:Female; D018392:Genomic Imprinting / Q000502:physiology*; D008297:Male; D053652:Nuclear Transfer Techniques; D010375:Pedigree