Final Report Summary - HDAC HEMATOPOIESIS (Role of Class IIa Histone deacetylases in hematopoietic cell differentiation)
Adult hematopoiesis is characterised by the generation of all blood cell types. To achieve this, Hematopoietic stem cells (HSCs) differentiate into Common myeloid progenitors (CMPs) and Lymphoid-primed multipotent progenitors (LMPPs). CMPs give rise to Megakaryocyte / erythrocyte progenitors (MEPs) and Granulocyte / macrophage progenitors (GMPs), whereas LMPPs still have the capacity to choose between the myelomonocytic and lymphoid lineages. Common lymphoid progenitors (CLPs) have the potential to differentiate into B and T lymphocytes, as well as Natural killer (NK) cells. Since the stability of every differentiation step is critical, each transition is tightly regulated at the transcriptional level through the action of lineage-restricted transcription factors that induce genes characteristic of particular cellular states. Surprisingly, very little is known on the role of gene transcriptional repressors, such as Histone deacetylases (HDACs), in the lineage specification and differentiation of hematopoietic cells.
The goal of my research proposal was to investigate the role of HDAC7 in lineage commitment and differentiation of hematopoietic cells. The specific objectives of the Marie Curie IRG project are:
- Objective 1. Identification of HDAC7 target genes in B cell precursors (pre-B cells) by ChIP-seq
- Objective 2. Role of HDAC7 during the reprogramming of pre-B cells into macrophages
- Objective 3. Role of HDAC7 in B cell development.
We have observed that, similar to B cell specific genes, HDAC7 expression is dramatically downregulated during the transdifferentiation of pre-B cells into macrophages. Co-immunoprecipitation experiments show that HDAC7 interacts with MEF2C and not with IKAROS, PAX5 and E2A in pre-B cells. Chromatin immunoprecipitation (ChIP) experiments show that HDAC7 is recruited to the MEF2 binding sites present in the promoter of key genes for myeloid cells. Re-expression of HDAC7 interferes with the transdifferentiation of pre-B cells into macrophages at both the functional level and the establishement of the myeloid genetic program.
To investigate the role of HDAC7 in B lymphocyte development in vivo we have performed a conditional knockout approach. We have observed that HDAC7 deletion in pro-B cells results in a block of B cell development at that developmental stage. Specifically we have found a diminished number of pre-B cells (CD43-) and a dramatic reduction of immature B cells (IgM+) in the bone marrow. In the spleen, we observe a severe impairment in the generation of B cells (B220+). No differences are observed in the number of thymocytes between knockout and littermate control mice. Taken together, these results demonstrate that HDAC7 is crucial for the development of B lymphocytes in vivo.
With the execution of the project we have identified the first lineage specific transcriptional repressor in the hematopoietic system. We have demonstrated that HDAC7 is recruited to and represses lineage inappropriate genes in B cell precursors. The down-regulation of HDAC7 is a critical event for the proper transdifferentiation of pre-B cells into macrophages. Using conditional knockout mice we have demonstrated that specific deletion of HDAC7 in pro-B cells results in a dramatic block in B cells development at the pro-B cell stage in the bone marrow. Taken together, the findings obtained with the execution of the Marie Curie IRG grant demonstrate that HDAC7 is a key transcriptional repressor for the development and identity of B lymphocytes.
The goal of my research proposal was to investigate the role of HDAC7 in lineage commitment and differentiation of hematopoietic cells. The specific objectives of the Marie Curie IRG project are:
- Objective 1. Identification of HDAC7 target genes in B cell precursors (pre-B cells) by ChIP-seq
- Objective 2. Role of HDAC7 during the reprogramming of pre-B cells into macrophages
- Objective 3. Role of HDAC7 in B cell development.
We have observed that, similar to B cell specific genes, HDAC7 expression is dramatically downregulated during the transdifferentiation of pre-B cells into macrophages. Co-immunoprecipitation experiments show that HDAC7 interacts with MEF2C and not with IKAROS, PAX5 and E2A in pre-B cells. Chromatin immunoprecipitation (ChIP) experiments show that HDAC7 is recruited to the MEF2 binding sites present in the promoter of key genes for myeloid cells. Re-expression of HDAC7 interferes with the transdifferentiation of pre-B cells into macrophages at both the functional level and the establishement of the myeloid genetic program.
To investigate the role of HDAC7 in B lymphocyte development in vivo we have performed a conditional knockout approach. We have observed that HDAC7 deletion in pro-B cells results in a block of B cell development at that developmental stage. Specifically we have found a diminished number of pre-B cells (CD43-) and a dramatic reduction of immature B cells (IgM+) in the bone marrow. In the spleen, we observe a severe impairment in the generation of B cells (B220+). No differences are observed in the number of thymocytes between knockout and littermate control mice. Taken together, these results demonstrate that HDAC7 is crucial for the development of B lymphocytes in vivo.
With the execution of the project we have identified the first lineage specific transcriptional repressor in the hematopoietic system. We have demonstrated that HDAC7 is recruited to and represses lineage inappropriate genes in B cell precursors. The down-regulation of HDAC7 is a critical event for the proper transdifferentiation of pre-B cells into macrophages. Using conditional knockout mice we have demonstrated that specific deletion of HDAC7 in pro-B cells results in a dramatic block in B cells development at the pro-B cell stage in the bone marrow. Taken together, the findings obtained with the execution of the Marie Curie IRG grant demonstrate that HDAC7 is a key transcriptional repressor for the development and identity of B lymphocytes.