Sus scrofa OPN gene was cloned by RT-PCR,its phylogenetic tree was constructed,and its expression was studied by semi-quantity RT-PCR combined Western-blot.The result showed that complete CDS of OPN was 909 bp,coded 303 amino acids,and its characteristic motifs included:(1) a potential calcium phosphate apatite binding region of eight consecutive Asp residues beginning at amino acid 86;(2) a cell-attachment Gly-Arg-Gly-Asp-Ser(GRGDS) sequence(residues 153-157);and(3) a thrombin RS cleavage site(residues 163 and 164).The phylogenetic tree showed that the relationship between S.scrofa and swine was the most close,but farthest between S.scrofa and Danio rerio.OPN gene experienced a wide variation during evolution.S.scrofa OPN mRNA was extensively expressed in different tissues,higher in heart,stomach,kidney,ovary,and lower in liver,spleen,lung,small intestine,muscle,and uterus.Different tissues expressed proteins with different weights and there were three patterns of expression,i.e.,70 ku,70 ku and 45 ku,as well as 70 ku,45 ku and 24 ku.