Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic cytokine that plays a crucial role
in the embryonic and postnatal development of various organs including the mammary gland. We
cloned bovine HGF and its c-Met receptor cDNAs, and examined their expression during mammary
gland development in dairy cows. The 2.5-kbp HGF cDNA clone contained a 2190 bp open reading
frame coding a 730 amino acid protein, while the 4.8-kbp c-Met cDNAclone contained a 4152 bp open
reading frame coding a 1384 amino acid protein. The bovine HGF and c-Met sequences exhibited
more than 87% identity with those of other mammals. RT-PCR analysis revealed ubiquitous expression
of both HGF and c-Met mRNAs in various bovine tissues tested. HGF mRNA was detected only
in the inactive stage of bovine mammary gland development and not in the developing, lactating, and
involuting stages, while c-Met mRNA was detected in the inactive and involuting stages. Immunohistochemical
analysis demonstrated that the c-Met protein was found on mammary epithelial cells in
the inactive, developing, and involuting stages, and on myoepithelial cells in all stages. These results
suggest pivotal roles of HGF and c-Met in the development of bovine mammary gland.
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