A newly identified gene MK, specifies for a heparin binding factor, is transiently expressed in the midgestation period of embryogenesis and in the early stages of embryonal carcinoma cell differentiation. In late embryos and the adult, MK gene is expressed only in the kidney. MK plays decisive roles not only in growth regulation but also in regulation of cell differentiation. The encoding sequence of mature peptide of MK was obtained by RT-PCR from human fetal kidney and was cloned into pBV221, after transfering into E.coli. A highly expressed vector of MK was constructed.