A gene encoding a polypeptide having an activity to support proliferation or survival of hematopoietic stem cells or hematopoietic progenitor cells is isolated by comparing expressed genes between cells which support proliferation or survival of hematopoietic stem cells or hematopoietic progenitor cells and cells which do not support the proliferation or survival. Proliferation or survival of hematopoietic stem cells or hematopoietic progenitor cells is supported by using stromal cells in which the isolated gene is expressed or a gene product of the isolated gene.