Expression of the mC26 gene encoding GlyCAM-1 in the lactating mouse mammary gland

We previously reported the partial sequence of a cloned genomic DNA, mC26, which codes for a protein highly expressed in the lactating mouse mammary gland [mC26: Satow et al. (1986) J. Biochem. 99, 1639-1643; partial sequence: Kawamura et al. (1987) J. Biochem. 101, 103-110]. In this study, we sequenced the EcoRI-HindIII fragment (5,394 bp) of this gene and found that this gene contains a sequence completely (100%) homologous to the cDNA sequence currently reported to code for GlyCAM-1, a putative ligand for L-selectin. We show by means of an RNA protection assay that the mRNA of this gene is expressed in the mammary glands of lactating mice as well as in the lymph nodes. Semi-quantitative analysis of expression of the mC26 gene in the mammary glands revealed that the amount of mRNA was not detectable in the early stage of pregnancy, increased in the late stage, and remained quite abundant during lactation. The potential role of this gene highly expressed in the mammary gland in a stage-specific and tissue-specific manner is discussed.