Functional role of Nuclear Fators-I in hematopoietic ontogenesis

Nuclear Factor I (NFI) transcriptional factors constitute a family of four members, NFI-A, B, C and X, known for their positive and negative transcriptional regulatory roles in a cell type and promoter specific context. We previously identified NFI-A as a relevant target of the myeloid regulator microRNA-223, then we found that its levels play a key role in directing hematopoietic progenitors to the erythroid or granulocytic lineage. This prompted us to examine whether the expression of NFI-A and/or other NFIs factors could regulate primitive and definitive hematopoiesis in vivo. To this end we initially studied the expression pattern of NFIs factors in different tissues and stages of embryo development of CD1 mice. Our preliminary results indicate that NFI-A presents the most interesting expression pattern among NFIs factors, being express in hematopoietic tissues earlier and at the highest level during embryo development. In addition, performing colony-forming progenitor assays, we found NFI-A expression in primitive erythroid progenitor and during definitive hematopoietic colonies production, implicating it in having a possible role in primitive and definitive hematopoiesis. To elucidate the role of NFI-A in hematopoiesis we used two different strains of NFI-A-/- mice: B6N31 and B6hyb129mice. Histological examinations of hematopoietic tissues of NFI-A-/- mice showed that Nfi-A disruption results in hypocellularity of hematopoietic compartment together with a marked decrease of M/E ratio. Genes expression analysis performed on B6N31 hematopoietic tissues indicates that NFI-A -/- mice have a delay in the repression of embryonic β-globins and a perinatal decrease in adult globins expression, suggesting an involvement for NFI-A in the control of β-globins switching. In addiction NFI-A -/- hematopoietic tissues presents an up-regulation of NFI-B expression, indicating its possible action as compensator of NFI-A. To investigate about the role of NFI-A in adult hematopoiesis, we performed complete blood counts of peripheral blood from adults B6N31 NFI-A +/- and we observed a decreased MCV, an increased RDW and a decreased MCH compared with adult NFI-A +/+ B6N31 mice, demonstrating an haploinsufficiency of NFI-A factor and an altered hemoglobin synthesis. These data indicates that NFI-A could be involved in the pathogenesis of hematological diseases, further underlying its importance in hematopoietic development.