Embryo cloning

Lee J, Inoue K, Ono R, Ogonuki N, Kohda T, Kaneko-Ishino T, Ogura A, Ishino F. Erasing genomic imprinting memory in mouse clone embryos produced from day 11.5 primordial germ cells. Development 2002 129 1807— 1817. 

The type of donor cell influences development of the cloned embryos. Zakhartchen-ko et al. [10] reported that nuclei from bovine ear skin fibroblasts supported better... 

The in vitro development of bovine cloned embryos was significantly improved by delayed activation with an electrical pulse for 4—6 h after fusion [18]. Other materials, including a calcium inducer (calcium iono-phore or ionomycin), a protein kinase inhibitor [6-dimethyl aminopurine (DMAP)] or a protein synthesis inhibitor (cyclohexa-mide or puromycin) were known oocyte activators. In cattle, incubation with cyclo-hexamide following exposure of the embryo to ionomycin or electrical pulses resulted in embryo development to term [19,... 

Experi- Activation condition Repro- 1 step medium 2" step medium No. of No. %) of cloned embryos... 

In order successfully to derive immuno-compatible human ES cells from a living donor, a reliable and efficient method for producing cloned embryos and ES isolation must be developed. Thomson et al. 

Cibelli, Jose B. Lanza, Robert B. West, Michael D., et al. (2001). The First Human Cloned Embryo. Scientific American 286 (1) 44—51. 

Pig cloning will thus have a marked impact on tire optimization of meat production and xenohansplantation. To clone pigs from differentiated cells, tire nuclei of porcine Sus scrofa) fetal fibroblasts were injected into enucleated oocytes, and the development was induced by electro activation. The transfer of 110 cloned embryos to foiu sunogate mothers produced an apparently normal female piglet. The clonal provenance of the piglet was indicated by her coat color and confirmed by DNA microsatellite analysis. 

Byme JA, Simonsson S, Gurdon JB (2002) From intestine to mnscle nuclear reprogramming through defective cloned embryos. Proc Natl Acad Sci USA 99 6059-6063. 

PEI D s, SUN Y H, CHEN s p, WANG Y p, HU w and ZHU z Y (2007a) Identification of differentially expressed genes from the cross-snbfamily cloned embryos derived from zebrafish nuclei and rare minnow enucleated eggs. Theriogenology, 68, 1282-1291. 

Uhm SJ, Gupta MK, Das ZC et al (2009) Effect of transgene introduction and recloning on efficiency of porcine transgenic cloned embryo production in vitro. Reprod Domest Anim... 

Uhm SJ, Gupta MK, Kim T et al (2007) Expression of enhanced green fluorescent protein in porcine- and bovine-cloned embryos following interspecies somatic cell nuclear transfer of fibroblasts transfected by retrovirus vector. Mol Reprod Dev 74 1538-1547... 

Somatic Cell Nuclear Transfer Implantation of nuclei from somatic (body) cells into an egg to make a cloned embryo. 

Therapeutic cloning uses the same procedures as reproductive cloning however, instead of transferring the cloned embryo into the womb of a surrogate mother, the embryo is further manipulated in the laboratory to make cell cultures of embryonic cells for basic or clinical research. 

After activation, the egg divides and grows like a newly formed embryo. However, if the animal is a mammal, the embryo can survive only for a limited period of time before it must implant into the inner layer of the mother s womb. Therefore, a surrogate female from the same species of the animal to be cloned, or a closely related species, is made pseudopregnant by feeding her hormones, and the embryo is released into her receptive womb, where it implants. Barring any technical or biological mishap, the cloned embryo will develop, and the process will result in a live birth. 

Therapeutic Cloning. To make embryonic cell cultures, cloned embryos are made by means of somatic cell nuclear transplantation. They are then either disassembled in the laboratory and used to establish embryonic cell cultures or gestated in a surrogate... 

By culturing specific cells from cloned embryos, scientists can make embryonic stem cell (ESC) cultures. During mammalian development, two distinct cell populations form after the first few days of embryonic development. The trophoblast, or the flattened, outer layer of cells, will eventually form the placenta and its associated structures. The inner cell mass (IGM) is the round, inner clump of cells that develop to form the embryo proper and a few structures associated with the placenta. If IGM cells are isolated and cultured on feeder cells, a layer of nondividing skin cells that secrete a cocktail of growth-promoting chemicals, the IGM cells will grow and spread over the surface of the culture dish. Such a culture is an embryonic stem cell culture, and these cells are pluripotent, which means that they can differentiate into any cell type in the adult body. 

Human cloning industries are working toward therapeutic cloning strategies. Advanced Cell Technologies (ACT) works on human cloning. Based in Worchester, Massachusetts, ACT seeks to produce patient-specific stem cells from cloned embryos and cloned fetuses that can cure degenerative diseases without the risk of rejection by the immune system. 

Bourc his, D., Le Bourhis, D., Patin, D. et al. 2001. Delayed and incomplete reprogramming of chromosome methylation patterns in bovine cloned embryos. CurrBiol 11(19) 1542-6. 

Dean, W., Santos, R, Stojkovic, M. et al. 2001. Conservation of methylation reprogramming in mammalian development Aberrant reprogramming in cloned embryos. Proc Natl Acad Sci USA 98(24) 13734-8. 

Dean, W., Santos, F, Stojkovic, M. et al. 2001. Conservation of methylation reprogramming in mammalian development Aberrant reprogramming in cloned embryos. Proc Natl Acad Sci USA 98(24) 13734-8. Doetschman, T., Eistetter, H., Katz, M., Schmidt, W., and Kemler, R. 1985. The in vitro development of blastocyst-derived embryonic stem cell lines Formation of visceral yolk sac, blood islands and myocardium. /Embryol Exp Morphol 87 27-45. 

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