title: Identifying genes preferentially expressed in undifferentiated embryonic stem cells.
abstract: BACKGROUND
  The mechanism involved in the maintenance and differentiation of embryonic stem (ES) cells is incompletely understood.
  
  
  RESULTS
  To address this issue, we have developed a retroviral gene trap vector that can target genes expressed in undifferentiated ES cells. This gene trap vector harbors both GFP and Neo reporter genes. G-418 drug resistance was used to select ES clones in which the vector was integrated into transcriptionally active loci. This was then followed by GFP FACS profiling to identify ES clones with reduced GFP fluorescence and, hence, reduced transcriptional activity when ES cells differentiate. Reduced expression of the GFP reporter in six of three hundred ES clones in our pilot screening was confirmed to be down-regulated by Northern blot analysis during ES cell differentiation. These six ES clones represent four different genes. Among the six integration sites, one was at Zfp-57 whose gene product is known to be enriched in undifferentiated ES cells. Three were located in an intron of a novel isoform of CSL/RBP-J kappa which encodes the key transcription factor of the LIN-12/Notch pathway. Another was inside a gene that may encode noncoding RNA transcripts. The last integration event occurred at a locus that may harbor a novel gene.
  
  
  CONCLUSIONS
  Taken together, we demonstrate the use of a novel retroviral gene trap vector in identifying genes preferentially expressed in undifferentiated ES cells.
authors.affiliation: Department of Genetics, Harvard Medical School, Boston, MA 02115, USA. xli@genetics.med.harvard.edu
authors.forename: Xiajun
authors.initials: X
authors.lastname: Li
authors.forename: Philip
authors.initials: P
authors.lastname: Leder
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression; D017930:Genes, Reporter; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice
chemical_list: D049452:Green Fluorescent Proteins