The Role of NFI-A in Hematopoietic Lineage Specification and Differentiation

Hematopoietic lineage commitment and differentiation is governed largely by a selective combination of transcription factors (TFs). The TF Nuclear Factor I-A (NFI-A) is a member of the NFI TF family that are known for their positive and negative transcriptional regulatory roles in a cell type and promoter specific context. NFI-A has a major role in brain development, and shows a unique pattern of expression in the developing mouse embryo. NFI-A was previously noted by our group as a relevant target of the myeloid regulator microRNA-223, whereas nothing is known on its role in normal human erythrogranulopoiesis. Here we have identified NFI-A as being necessary for directing hematopoietic progenitors (HPCs) to the erythroid (E) or granulocytic (G) lineage. In cord blood CD34+ HPCs placed in hematopoietic unilineage culture differentiation systems, we demonstrated a lineage specific expression pattern of NFI-A: during E differentiation it is strongly upregulated whereas during G differentiation is markedly downregulated. Using lentiviral vectors encoding NFI-A and siNFI-A for expression in myeloid cell lines and in CD34+ HPCs, we showed that NFI-A is required for E differentiation and its overexpression enhances E differentiation under suboptimal erythropoietin concentrations. Conversely, the silencing of NFI-A during unilineage G differentiation is required as its overexpression blocks G differentiation. Using an (E+G) bilineage culture system exogenous manipulation of NFI-A was found to direct HPCs to the E or G fate. Finally, a dual and opposite transcriptional action of NFI-A was identified by activating the β-globin promoter and repressing G-CSF receptor expression. Our current microarray based studies implicate NFI-A in upregulating a subset of erythroid genes in CD34+ transduced HPCs (related to globin and heme biosynthesis and important erythrocyte membrane structural proteins). Ongoing characterization of NFI-A during hematopoietic ontogeny in the mouse implicates it in possibly having a role in primitive erythropoiesis and future studies using NFI-A-/- mice in combination with lentiviral technology will allow a deep examination of NFI-A function during both primitive and definitive embryonic hematopoiesis. Our data indicating the necessity of proper levels of NFIA during hematopoietic differentiation of erythroid and granulocytic compartments indicates that NFI-A could be involved in the pathogenesis of haematological diseases further underlying its importance in hematopoietic development.