The allele was generated by inserting 2 loxP sites downstream of exon 3 and exon 7 of the Thbs1 gene, respectively. An FRT (flippase recognition target) site flanked neomycin positive selection cassette was also included right before the 3-loxP site. After homologous recombination in SV129-derived ES cells, the neomycin cassette was removed prior to injection of recombinant cells into C57BL/6 blastocysts. (J:318633)