By analyzing hematopoietic stem cell proliferation regulators produced by stroma cells, a cDNA library is constructed and novel hematopoiesis-associated genes are isolated. Genes encoding the proteins as specified in the following (a) or (b): (a) having an amino acid sequence represented by one of SEQ ID NOS selected from the group consisting of SEQ ID NOS: 2, 4, 6, 8, 10 and 12; or (b) having an amino acid sequence derived from the amino acid sequence as defined in the above (a) by deletion, substitution or addition of one to several amino acids and having an activity of regulation hematopoietic stem cell proliferation.