TFPI targeting vector with 5′ DNA probe Southern blot screening. (A) Schematic representation of the introduction of the targeting vector and subsequent removal of the PGK-NEO cassette using flippase-mediated flippase recombination target site. (B) 129Sv/J embryonic stem cells were screened for successful targeting of TFPI exon 4 using Southern blot analysis that used a 5′ DNA probe differentiating wild-type and floxed alleles. (C) Germline transmission of the targeting vector was also assessed using Southern blot screening.