Engineering MAPT transgenes in responder mouse lines: A schematic illustration. Col1A1, collagen; Type I, α1 gene; 3′-UTR, the three prime untranslated region; G418^R, an open reading frame encoding aminoglycoside phosphotransferase from the Tn5 transposon that confers resistance to geneticin; FRT, flippase (FLP) recognition target; Hygro^R, an open reading frame encoding aminoglycoside phosphotransferase from E. coli that confers resistance to hygromycin; Pgk promoter, the mouse phosphoglycerate kinase 1 promoter; ATG, the start codon; Prnp/MAPT, DNA sequence encoding the 0N4R isoform of human tau inserted in the mouse prion protein gene encoding partial introns 1 and 2 plus exons 2-3; SV40 poly(A), simian virus 40 polyadenylation tail; CAG promoter, a synthetic promoter engineered from the cytomegalovirus early enhancer element, the chicken β-actin promoter, and the splice acceptor of the rabbit β-globin gene; FLPe, an open reading frame encoding a fusion between simian virus 40 nuclear localization signal and the S. cerevisiae site-specific recombinase FLP.