Targeting strategy to generate the Gp1ba-Cre mouse. The mouse Gp1ba gene consists of a 5′ untranslated exon (1), followed by a short intron and an exon (2) containing the open reading frame encoding GPIbα protein.⁵⁸  The targeting strategy enables the generation of a constitutive KI of a T2A-iCre in the endogenous Gp1ba locus. The sequences for the T2A and the open reading frame of iCre have been inserted between the last amino acid and the translation termination codon in exon 2 of Gp1ba. Puromycin resistance (positive selection marker) is flanked by FRT sites and inserted downstream of the mouse 3′ untranslated region. The constitutive KI allele is obtained after in vivo Flp-mediated removal of the selection marker and expresses a chimeric transcript harboring the iCre gene fused to the Gp1ba gene via the T2A sequence. TK, thymidine kinase.