As the CXCR4 expression on HSPCs has been shown to increase in patients with MDS, we hypothesized that the CXCR4 expression level may be useful for discriminating clonal hematopoiesis by healthy HSPCs from premalignant clonal hematopoiesis by HSPCs with somatic mutations. The gene discussed is CXCR4; the disease is myelodysplastic syndrome.