The line was obtained by microinjection of a circular murine BAC transgene (RP23-53E2) previously modified by recombineering at the ATG of the Col1a1 gene of a rabbit-beta-globin intron-cre/ERT2 cassette followed by a flipped PGK-Tn5-Kana/NeoR cassette. The subline 6.1 was analyzed and cryopreserved.