A paper, by US researchers from U. Missouri, Immerge BioTheraputics and Korean researchers, appearing in the 08 Feb 2002 issue of _Science_.

Title: Production of ... Knockout Pigs by Nuclear Transfer Cloning

Summary: Shortages in human organs for transplantation has led to consideration of other species as possible donors. The ability to use pig organs has been hampered by the presence of galactose a-1,3-galactose residues on the surface of pig cells, which result in their rejection by primate recipients, who lack the enzyme that creates this linkage. Lai et al. (p. 1089) knocked out one allele of the a-1,3-galactosyltransferase in fetal fibroblasts in vitro and then used these cells to clone transgenic pigs by nuclear transfer. The next step will be the creation of a homozygous pig that completely lacks these residues. In addition to their eventual impact in the field of xenotransplantation, these pigs serve as models for genetic modifications of the porcine genome for other medical and agricultural purposes.