EHA Library - The official digital education library of European Hematology Association (EHA)

A NOVEL ROLE FOR IRON REGULATORY PROTEINS IN HEMATOPOIESIS
Author(s): ,
Michael Bonadonna
Affiliations:
virus-associated carcinogenesis,German Cancer Research Center,Heidelberg,Germany
,
Elisabeth Tybl
Affiliations:
virus-associated carcinogenesis,German Cancer Research Center,Heidelberg,Germany
,
Gael Palais
Affiliations:
virus-associated carcinogenesis,German Cancer Research Center,Heidelberg,Germany
,
Ruzhica Bogeska
Affiliations:
Heidelberg Institute for Stem Cell Technology and Experimental Medicine,Heidelberg,Germany
,
Sandro Altamura
Affiliations:
Department of Pediatric Hematology, Oncology and Immunology,University of Heidelberg,Heidelberg,Germany
,
Michael Milsom
Affiliations:
Division of Experimental Hematology,German Cancer Research Center,Heidelberg,Germany
Bruno Galy
Affiliations:
virus-associated carcinogenesis,German Cancer Research Center,Heidelberg,Germany
(Abstract release date: 05/14/20) EHA Library. Galy B. 06/12/20; 294924; S104
Bruno Galy
Bruno Galy
Contributions
Abstract

Abstract: S104

Type: Presidential Symposium

Session title: Presidential Symposium

Background

Research in the past few years uncovered the critical importance of metabolism for the control of stem cell behavior and lineage specification in the hematopoietic system. While much of the focus has been on intermediary and energy metabolism, the role of trace elements such as iron in hematopoietic cell fate decisions remains ill understood. The metal is known to be critical for hemoglobin synthesis and thus for erythropoiesis. Yet, iron is a co-factor required for a plethora of metabolic processes, raising the question of its importance for other aspects of hematopoiesis.

Aims

In mammals, cellular iron homeostasis is orchestrated posttranscriptionally by the iron regulatory proteins (IRP)-1 and -2, which control the fate of mRNAs encoding key iron management proteins in the cell. In the present study, we sought to determine the role of IRP-mediated iron homeostasis for steady-state adult hematopoiesis, using mouse reverse genetics.

Methods

We generated a mouse model enabling acute disruption of IRP function in the entire body during adulthood, based on Cre/LoxP technology. We used multi-color flow cytometry to determine the impact of IRP deficiency on the cellular composition of the hematopoietic system. Specific hematopoietic cell populations were sorted by FACS, and their transcriptome was analyzed using RNA-Seq (RNA sequencing) together with gene/functional enrichment clustering approaches. Reciprocal bone-marrow chimeric mice were created to study the selective role of IRPs in hematopoietic versus non-hematopoietic tissues. Finally, hematopoietic progenitor cells derived from IRP-mutant mice were grown and differentiated ex vivo to investigate the cell intrinsic functions of the IRPs in neutropoiesis.

Results

Acute, body-wide disruption of IRP function results in bone marrow aplasia, associated with a decrease in the number of both myeloid cells and erythrocytes in peripheral blood. Flow cytometry analysis of bone marrow cells revealed an enlargement of the stem cell compartment as well as of early and common progenitor cells, possibly reflecting an attempt of the hematopoietic process to replenish the blood system. Yet, this response does not result in expansion of differentiated cells, and is on the contrary accompanied by a decrease in the abundance of erythroid and myeloid cells, more specifically granulocytes. Indeed, we observed impaired progression of erythroid precursors from the baso- to the poly- and ortho-chromatic stages, most likely due to functional iron insuficiency. Importantly, hematopoietic progenitor cells also fail to differentiate into granulocytes, and instead give rise to seemingly “immature” neutrophils. Based on reciprocal bone marrow transplantation experiments in vivo and an ex vivo cell culture model, we could demonstrate that IRPs support neutrophil differentiation in a cell intrinsic manner. Furthermore, transcriptome profiling suggests that IRPs may be important for adequate remodeling of cellular metabolism during neutrophil differentiation in the bone marrow.

Conclusion

IRPs seem not strictly required for the multiplication of stem and progenitor cells, but are critical at later stages of hematopoiesis, in particular for the development of neutrophils. This work uncovers a previously unrecognized role for the IRPs and iron metabolism in adult hematopoiesis, beyond the making of red blood cells.

Session topic: 29. Iron metabolism, deficiency and overload

Keyword(s): Granulopoiesis, Hematopoiesis, Iron metabolism

Abstract: S104

Type: Presidential Symposium

Session title: Presidential Symposium

Background

Research in the past few years uncovered the critical importance of metabolism for the control of stem cell behavior and lineage specification in the hematopoietic system. While much of the focus has been on intermediary and energy metabolism, the role of trace elements such as iron in hematopoietic cell fate decisions remains ill understood. The metal is known to be critical for hemoglobin synthesis and thus for erythropoiesis. Yet, iron is a co-factor required for a plethora of metabolic processes, raising the question of its importance for other aspects of hematopoiesis.

Aims

In mammals, cellular iron homeostasis is orchestrated posttranscriptionally by the iron regulatory proteins (IRP)-1 and -2, which control the fate of mRNAs encoding key iron management proteins in the cell. In the present study, we sought to determine the role of IRP-mediated iron homeostasis for steady-state adult hematopoiesis, using mouse reverse genetics.

Methods

We generated a mouse model enabling acute disruption of IRP function in the entire body during adulthood, based on Cre/LoxP technology. We used multi-color flow cytometry to determine the impact of IRP deficiency on the cellular composition of the hematopoietic system. Specific hematopoietic cell populations were sorted by FACS, and their transcriptome was analyzed using RNA-Seq (RNA sequencing) together with gene/functional enrichment clustering approaches. Reciprocal bone-marrow chimeric mice were created to study the selective role of IRPs in hematopoietic versus non-hematopoietic tissues. Finally, hematopoietic progenitor cells derived from IRP-mutant mice were grown and differentiated ex vivo to investigate the cell intrinsic functions of the IRPs in neutropoiesis.

Results

Acute, body-wide disruption of IRP function results in bone marrow aplasia, associated with a decrease in the number of both myeloid cells and erythrocytes in peripheral blood. Flow cytometry analysis of bone marrow cells revealed an enlargement of the stem cell compartment as well as of early and common progenitor cells, possibly reflecting an attempt of the hematopoietic process to replenish the blood system. Yet, this response does not result in expansion of differentiated cells, and is on the contrary accompanied by a decrease in the abundance of erythroid and myeloid cells, more specifically granulocytes. Indeed, we observed impaired progression of erythroid precursors from the baso- to the poly- and ortho-chromatic stages, most likely due to functional iron insuficiency. Importantly, hematopoietic progenitor cells also fail to differentiate into granulocytes, and instead give rise to seemingly “immature” neutrophils. Based on reciprocal bone marrow transplantation experiments in vivo and an ex vivo cell culture model, we could demonstrate that IRPs support neutrophil differentiation in a cell intrinsic manner. Furthermore, transcriptome profiling suggests that IRPs may be important for adequate remodeling of cellular metabolism during neutrophil differentiation in the bone marrow.

Conclusion

IRPs seem not strictly required for the multiplication of stem and progenitor cells, but are critical at later stages of hematopoiesis, in particular for the development of neutrophils. This work uncovers a previously unrecognized role for the IRPs and iron metabolism in adult hematopoiesis, beyond the making of red blood cells.

Session topic: 29. Iron metabolism, deficiency and overload

Keyword(s): Granulopoiesis, Hematopoiesis, Iron metabolism

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