The Mouse Homeobox Gene, Gbx2: Genomic Organisation and Expression in Pluripotent Cells in Vitro and in Vivo

Abstract

The Gbx2 homeodomain is widely conserved in metazoans. We investigated the mouseGbx2locus by isolation and characterization of genomic clones and by physical localization to the genome. TheGbx2gene contained a single intron that separated the proposed functional protein domains. This organization was conserved with humanGBX2.Physical localization ofGbx2to Chromosome 1C5–E1 indicated that the genomic relationship between the linkedGbx2andEn1genes differs between mouse and human, making it unlikely to be of functional significance. We also extended the known expression pattern ofGbx2beyond the gastrulation stage embryo and the developing CNS to pluripotent cellsin vitroandin vivo. Gbx2expression was demonstrated in undifferentiated embryonic stem cells but was downregulated in differentiated cell populations. In the embryo,Gbx2expression was detected before primitive streak formation, in the inner cell mass of the preimplantation embryo.Gbx2is therefore a candidate control gene for cell pluripotency and differentiation in the embryo.