Construction of recombinant plasmid and pcDNA3.1 vector.. A) 1% Agarose DNA gel electrophoresis for three positive TA clone plasmids digested by restriction enzyme EcoR I and Kpn I; lane 1 to lane 3: three positive TA clone plasmids; lane M: DL-3000 marker. B) 1% Agarose DNA gelelectrophoresis for pcDNA3.1-CD44st digested with two restriction enzymes: EcoR I and Kpn I; lane 1 to lane 3: three positive plasmids, respectively; lane M: DL-10000 Marker.[9, 10, 19]. B) (1) Standard CD44, which lacks the entire variable region. (2) pMeta-1; Exons v4 to v7 were inserted in turn into the intermediate part of exons 5 and 17. (3) pMeta-2; Exons v6 and v7 were interposed between exons 5 and 17 . DNA sequencing confirmed that the reconstructed plasmid contained the sequence of the CD44st gene, which was composed of exons 1 to 4, exons 16 to 17, and 1 to 205 bases of 20 exons (Figure 2). The new gene sequence was sent to the National Center for Biotechnology Information (NCBI) for publication and registered with the number FJ216964.