title: Efficient selection of Gal-knockout pig cells for somatic cell nuclear transfer.
abstract: BACKGROUND
  The process of selecting transgenic cells has been one of the bottlenecks in the generation of transgenic animals by somatic cell nuclear transfer (SCNT). In particular, selection for the Gal double-knockout (Gal-DKO) genotype has been time consuming and inefficient. The objective of this work was to generate a highly efficient system to select Gal-DKO cells to be used in SCNT without affecting the efficiency in production of Gal-null pigs.
  
  
  METHODS
  Fetal liver-derived cells deficient in Gal-expression were initially selected by fluorescence-activated cell sorting (FACS) using IB4 conjugated to a fluorescent dye. Cells recovered by FACS were cultured and expanded, followed by a second round of selection using streptavidin magnetic beads and IB4 lectin biotin.
  
  
  RESULTS
  Recovery efficiency of target cells was 0.04% for the first selection using FACS and 0.3% for the second round by magnetic beads. Full reprogramming was obtained on selected Gal-DKO cells after FACS and magnetic beads selection, when used for SCNT to produce the Gal-null piglets. Cells obtained from magnetic beads developed 48 colonies; the Gal-null genotype was found in 44 of them (91.7%). Three of these colonies were used to generate piglets by SCNT. From three recipients receiving embryos, two became pregnant and produced 17 piglets, all of them DKO.
  
  
  CONCLUSIONS
  Sequential selection of Gal-DKO cells by FACS/magnetic beads is a highly efficient system to generate null cells. Selected cells were successfully used to generate healthy double-knockout piglets by SCNT.
authors.affiliation: Department of Surgery, Transplant Surgery Section, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Luz M
authors.initials: LM
authors.lastname: Reyes
authors.forename: Jose L
authors.initials: JL
authors.lastname: Estrada
authors.forename: Bess
authors.initials: B
authors.lastname: Ivary
authors.forename: Richard A
authors.initials: RA
authors.lastname: Sidner
authors.forename: Leela L
authors.initials: LL
authors.lastname: Paris
authors.forename: A Joseph
authors.initials: AJ
authors.lastname: Tector
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002478:Cells, Cultured; D005434:Flow Cytometry; D005700:Galactosyltransferases / Q000172:deficiency* / Q000235:genetics; D008099:Liver / Q000166:cytology* / Q000196:embryology; D008280:Magnetics; D023421:Models, Animal; D053652:Nuclear Transfer Techniques; D013552:Swine
chemical_list: D005700:Galactosyltransferases
keywords: Double-selection; FACS; Gal-KO; Magnetic beads; SCNT; Swine