Detection of Smad5 mRNA in the immortalized myeloid leukemia cell lines KG1 and HL-60, as well as low density mononuclear, high density polymorphonuclear and CD34⁺ selected cells isolated from normal human BM. The entire coding region of Smad5 was amplified by PCR from RNA isolated from the various sources and analyzed on an agarose gel. In all cell populations analyzed, a single band representing the full length coding region was found.