Polypeptide growth factors, methods of making them, polynucleotides encoding them, antibodies to them, and methods of using them are disclosed. The polypeptides comprise an amino acid segment that is at least 70% identical to residues 52-179 of SEQ ID NO:2 or residues 258-370 of SEQ ID NO:2. Multimers of the polypeptides are also disclosed. The polypeptides, multimeric proteins, and polynucleotides can be used in the study and regulation of cell and tissue development, as components of cell culture media, and as diagnostic agents.