Direct and rapid modification of a porcine xenoantigen gene (GGTA1).

The ability to modify animal genomes rapidly at a specific locus would be valuable both for research purposes and in the development of animals suitable for xenotransplantation. In a proof-of-concept study, we used a unique, homology-dependent strand transferase protein called drosophila recombination-associated protein (DRAP) and DNA oligonucleotides to modify the porcine gene encoding alpha 1,3 galactosyl transferase (GGTA1). This gene is responsible for generating xenotransplantation antigens resulting in hyperacute rejection.

Production of alpha-1,3-galactosyltransferase null pigs by means of nuclear transfer with fibroblasts bearing loss of heterozygosity mutations.

Hyperacute rejection of porcine organs by old world primate recipients is mediated through preformed antibodies against galactosyl-alpha-1,3-galactose (Galalpha-1,3-Gal) epitopes expressed on the pig cell surface. Previously, we generated inbred miniature swine with a null allele of the alpha-1,3-galactosyltransferase locus (GGTA1) by nuclear transfer (NT) with gene-targeted fibroblasts. To expedite the generation of GGTA1 null pigs, we selected spontaneous null mutant cells from fibroblast cultures of heterozygous animals for use in another round of NT.

Ontogeny of cloned cattle to lactation.

Central to the success of large animal cloning is the production of healthy animals that can provide products for human health, food, and other animal agriculture applications. We report development of cloned cattle derived from 34 genetically unique, nonembryonic cell lines using nuclear transfer performed between 1 January 1998 and 29 February 2000. Nearly 25% (535/2170) of the recipients receiving reconstructed embryos initiated pregnancy.

Production of cloned cattle from in vitro systems.

The pregnancy initiation and maintenance rates of nuclear transfer embryos produced from several bovine cell types were measured to determine which cell types produced healthy calves and had growth characteristics that would allow for genetic manipulation. Considerable variability between cell types from one animal and the same cell type from different animals was observed. In general, cultured fetal cells performed better with respect to pregnancy initiation and calving than adult cells with the exception of cumulous cells, which produced the highest overall pregnancy and calving rates.