The present invention provides SELF protein having controlling effects on growth and differentiation of undifferentiated cells, wherein the protein contains a novel EGF-like repeat sequence, SELF gene encoding the same, a recombinant vector and a transformed cell containing the SELF gene, a method for treatment or prophylaxis with SELF protein or a recombinant expression vector containing SELF gene, SELF promoter, a recombinant vector and a transformed cell containing SELF promoter, and a screening method using the transformed cell containing SELF promoter.