Endoglin gene-trapped clone. (A) Sequences of 5′ and 3′ RACE products. Lowercase letters represent endoglin cDNA sequence, including cording region (bold). Capital letters represent En2 splice acceptor (5′ RACE) or Pax2 splice donor sequence (3′ RACE) derived from the gene-trap vector. Underline indicates a Pax2 intronic sequence. (B) Schematic representation of genomic structure of endoglin wild-type and gene-trapped loci. Boxes represent exons, and the cording region is filled. The integration site of the gene-trap vector is indicated by an asterisk. B indicates BamHI; H, HindIII; X, XbaI. (C) In vitro expression of lacZ reporter for endoglin. EF indicates undifferentiated ES cells on embryonic fibroblast; EB, embryoid body; days 4, 5, and 6, differentiated ES cells on the OP9 feeder cell layer. Scale bars, 50 μm.