Schematic representation of the MαIIbtk transgene. The proximal promoter region of the murine α_IIb gene (up to the EcoR1 site) was amplified by PCR to mutate the endogenous α_IIb ATG initiation codon (at position +32) to ATC. The distal 5′-flanking region was then added to replace the PGK promoter in pPNT plasmid. The tk gene starts at site HincII (open box). The 4.2-kb HindIII fragment excised from the plasmid for the production of transgenic animals is represented by arrows.