The GPI-anchored protein CD109 protects hematopoietic progenitor cells from undergoing erythroid differentiation induced by TGF-β.

Although a glycosylphosphatidylinositol-anchored protein (GPI-AP) CD109 serves as a TGF-β co-receptor and inhibits TGF-β signaling in keratinocytes, the role of CD109 on hematopoietic stem progenitor cells (HSPCs) remains unknown. We studied the effect of CD109 knockout (KO) or knockdown (KD) on TF-1, a myeloid leukemia cell line that expresses CD109, and primary human HSPCs. CD109-KO or KD TF-1 cells underwent erythroid differentiation in the presence of TGF-β. CD109 was more abundantly expressed in hematopoietic stem cells (HSCs) than in multipotent progenitors and HSPCs of human bone marrow (BM) and cord blood but was not detected in mouse HSCs. Erythroid differentiation was induced by TGF-β to a greater extent in CD109-KD cord blood or iPS cell-derived megakaryocyte-erythrocyte progenitor cells (MEPs) than in wild-type MEPs. When we analyzed the phenotype of peripheral blood MEPs of patients with paroxysmal nocturnal hemoglobinuria who had both GPI(+) and GPI(-) CD34+ cells, the CD36 expression was more evident in CD109- MEPs than CD109+ MEPs. In summary, CD109 suppresses TGF-β signaling in HSPCs, and the lack of CD109 may increase the sensitivity of PIGA-mutated HSPCs to TGF-β, thus leading to the preferential commitment of erythroid progenitor cells to mature red blood cells in immune-mediated BM failure.