Complex Interactions in Regulation of Haematopoiesis—An Unexplored Iron Mine

Iron is one of the most abundant metals on earth and is vital for the growth and survival of life forms. It is crucial for the functioning of plants and animals as it is an integral component of the photosynthetic apparatus and innumerable proteins and enzymes. It plays a pivotal role in haematopoiesis and affects the development and differentiation of different haematopoietic lineages, apart from its obvious necessity in erythropoiesis. A large amount of iron stores in humans is diverted towards the latter process, as iron is an indispensable component of haemoglobin. This review summarises the important players of iron metabolism and homeostasis that have been discovered in recent years and highlights the overall significance of iron in haematopoiesis. Its role in maintenance of haematopoietic stem cells, influence on differentiation of varied haematopoietic lineages and consequences of iron deficiency/overloading on development and maturation of different groups of haematopoietic cells have been discussed.

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Ernest Armstrong McCulloch. 21 April 1926—20 January 2011

Biographical Memoirs of Fellows of the Royal Society ◽

10.1098/rsbm.2017.0019 ◽

2017 ◽

Vol 64 ◽

pp. 317-339

Author(s):

Tak Wah Mak

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Blood Disorders ◽

Haematopoietic Stem Cells ◽

Vast Array ◽

Cellular Physiology ◽

Haematopoietic Cells ◽

The World ◽

Big Picture ◽

Dual Capacity

Ernest Armstrong McCulloch was half of the brilliant partnership that discovered haematopoietic stem cells (HSCs) and changed how we think about human tissue generation and regeneration. Based at the Ontario Cancer Institute (now the Princess Margaret Cancer Centre) in Toronto, the haematologist ‘Bun’ McCulloch, together with James E. Till, a physicist with a steel-trap mind, exercised their penchant for adventurous ‘big picture’ thinking in devising experiments to identify stem cells. This exceptional team was the first to demonstrate that HSCs have the dual capacity to self-renew and to differentiate into a vast array of mature haematopoietic cells. Their trainees, as well as investigators elsewhere, built on McCulloch and Till's findings not only to isolate and characterize HSCs and progenitors derived from them, but also to devise therapies for certain blood disorders. Later in his career, Ernest focused on characterizing the malignant cells of human leukaemias and determining the effects of various drugs on leukaemic cell growth. The implications of Till and McCulloch's work continue to be profound and underpin many significant breakthroughs in our knowledge of normal cellular physiology, pathophysiology, tumorigenesis and tissue transplantation. Indeed, regenerative medicine owes its very existence to the stem cell discoveries of McCulloch, Till and others. At times eccentric and demanding, but always well spoken, incisive and erudite, Ernest personified the outstanding research scientist cloaked in Canadian modesty. His legacy lives on in the bright therapeutic future emerging from the rigorous stem cell research being conducted in Canada and around the world.

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Transcriptional Regulation of the LMO2 T-Cell Leukaemia Oncogene.

Blood ◽

10.1182/blood.v106.11.2728.2728 ◽

2005 ◽

Vol 106 (11) ◽

pp. 2728-2728

Author(s):

Josette-Renée Landry ◽

Sarah Kinston ◽

Kathy Knezevic ◽

Anthony R. Green ◽

Berthold Göttgens

Keyword(s):

Stem Cells ◽

T Cell ◽

Cell Lines ◽

Molecular Mechanisms ◽

Regulatory Elements ◽

Proximal Promoter ◽

Cell Leukaemia ◽

Haematopoietic Stem Cells ◽

Haematopoietic Cells

Abstract Transcriptional control has long been identified as a key mechanism regulating the formation and subsequent behaviour of haematopoietic stem cells. We have used a comparative genomics approach to identify transcriptional regulatory elements of the LMO2 gene, a transcriptional cofactor originally identified through its involvement in T-cell leukaemia and subsequently shown to be critical for the formation of haematopoietic stem cells and endothelial development. An initial stringent search for homology between evolutionary distant species demonstrated that, apart from the coding exons, high level of identity between mammalian, amphibian and fish sequences was restricted to the proximal promoter region of LMO2. Real-time RT-PCR expression analysis identified this promoter as the predominant source of transcription in haematopoietic tissue. Transient and stable transfections indicated that the proximal promoter was active in haematopoietic progenitor and endothelial cell lines and this activity was shown to depend on three conserved Ets sites which were bound in vivo by Elf1, Fli1 and Ets1. Transgenic analysis demonstrated that the LMO2 proximal promoter was sufficient for expression in endothelial cells in vivo. However, no haematopoietic expression was observed indicating that additional enhancers are required to mediate transcription from the proximal promoter in haematopoietic cells. To identify additional elements involved in haematopoietic expression of LMO2, we have performed a less restrictive search for conserved sequences by comparing the human, dog, rat and mouse LMO2 loci to the marsupial opossum LMO2 locus. The addition of the opossum locus, and removal of the more distant fish and amphibian sequences from the alignment, resulted in the discovery of eleven conserved regions. These sequences represent candidate haematopoietic regulatory regions as they contain conserved transcription factor binding sites (E boxes, Ets and Gata sites) previously shown to regulate several other haematopoietic genes. We will present results from a systematic analysis of these regions for enhancer activity in both haematopoietic cell lines and transgenic mice, which suggest that several of these elements indeed act as enhancers. Taken together, our experiments will provide a framework for the transcriptional hierarchies within which LMO2 exerts its function in normal haematopoietic cells. Moreover, the current studies will serve as a platform to examine potential molecular mechanisms that can cause ectopic expression of LMO2 in T-cell progenitors with the ultimate consequence of developing T-ALL.

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MAEA is an E3 ubiquitin ligase promoting autophagy and maintenance of haematopoietic stem cells

Nature Communications ◽

10.1038/s41467-021-22749-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Qiaozhi Wei ◽

Sandra Pinho ◽

Shuxian Dong ◽

Halley Pierce ◽

Huihui Li ◽

...

Keyword(s):

Stem Cells ◽

Ubiquitin Ligase ◽

Kinase Inhibitor ◽

E3 Ubiquitin Ligase ◽

Surface Expression ◽

Haematopoietic Stem Cells ◽

Receptor Signalling ◽

Haematopoietic Cells ◽

Ubiquitin Ligase Activity ◽

Proliferation And Differentiation

AbstractHaematopoietic stem cells (HSCs) tightly regulate their quiescence, proliferation, and differentiation to generate blood cells during the entire lifetime. The mechanisms by which these critical activities are balanced are still unclear. Here, we report that Macrophage-Erythroblast Attacher (MAEA, also known as EMP), a receptor thus far only identified in erythroblastic island, is a membrane-associated E3 ubiquitin ligase subunit essential for HSC maintenance and lymphoid potential. Maea is highly expressed in HSCs and its deletion in mice severely impairs HSC quiescence and leads to a lethal myeloproliferative syndrome. Mechanistically, we have found that the surface expression of several haematopoietic cytokine receptors (e.g. MPL, FLT3) is stabilised in the absence of Maea, thereby prolonging their intracellular signalling. This is associated with impaired autophagy flux in HSCs but not in mature haematopoietic cells. Administration of receptor kinase inhibitor or autophagy-inducing compounds rescues the functional defects of Maea-deficient HSCs. Our results suggest that MAEA provides E3 ubiquitin ligase activity, guarding HSC function by restricting cytokine receptor signalling via autophagy.

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MAEA is an E3 ubiquitin ligase promoting autophagy and maintenance of haematopoietic stem cells

10.21203/rs.3.rs-123031/v1 ◽

2020 ◽

Author(s):

Qiaozhi Wei ◽

Sandra Pinho ◽

Shuxian Dong ◽

Halley Pierce ◽

Fumio Nakahara ◽

...

Keyword(s):

Stem Cells ◽

Ubiquitin Ligase ◽

Kinase Inhibitor ◽

E3 Ubiquitin Ligase ◽

Surface Expression ◽

Haematopoietic Stem Cells ◽

Haematopoietic Cells ◽

Ubiquitin Ligase Activity ◽

Proliferation And Differentiation ◽

And Function

Abstract Haematopoietic stem cells (HSCs) tightly regulate their quiescence, proliferation, and differentiation to generate blood cells during the entire lifetime. The mechanisms by which these critical activities are balanced are still unclear. Here, we report that Macrophage-Erythroblast Attacher (MAEA, also known as EMP), a receptor thus far only identified in erythroblastic island1, is a membrane-associated E3 ubiquitin ligase subunit essential for HSC maintenance and lymphoid commitment. Maea is highly expressed in HSCs and its deletion in mice severely impairs HSC quiescence and function and leads to a lethal myeloproliferative syndrome. Mechanistically, we have found that the surface expression of several haematopoietic cytokine receptors (e.g. MPL, FLT3) is stabilised in the absence of Maea, thereby prolonging their intracellular signalling. This is associated with impaired autophagy flux in HSCs, but not in mature haematopoietic cells. Administration of receptor kinase inhibitor or autophagy-inducing compounds rescues the functional defects of Maea-deficient HSCs. These results suggest that MAEA provides E3 ubiquitin ligase activity, guarding HSC function by restricting cytokine receptor signalling via autophagy.

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Deletion of IKK2 in haematopoietic cells of adult mice leads to elevated interleukin-6, neutrophilia and fatal gastrointestinal inflammation

Cell Death and Disease ◽

10.1038/s41419-020-03298-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Karla C. Fischer ◽

Carmel P. Daunt ◽

Cédric S. Tremblay ◽

Sheila Dias ◽

James E. Vince ◽

...

Keyword(s):

Stem Cells ◽

Interleukin 6 ◽

Critical Role ◽

Tumour Necrosis Factor Receptor ◽

Haematopoietic Stem Cells ◽

Haematopoietic Cells ◽

Haematopoietic Cell ◽

Iκb Kinase ◽

Recombination System ◽

Gastrointestinal Inflammation

AbstractThe IκB kinase complex, consisting of IKK1, IKK2 and the regulatory subunit NEMO, is required for NF-κB signalling following the activation of several cell surface receptors, such as members of the Tumour Necrosis Factor Receptor superfamily and the Interleukin-1 Receptor. This is critical for haematopoietic cell proliferation, differentiation, survival and immune responses. To determine the role of IKK in the regulation of haematopoiesis, we used the Rosa26Cre-ERT2 Cre/lox recombination system to achieve targeted, haematopoietic cell-restricted deletion of the genes for IKK1 or IKK2 in vivo. We found that the IKK complex plays a critical role in haematopoietic cell development and function. Deletion of IKK2, but not loss of IKK1, in haematopoietic cells led to an expansion of CD11b/Gr-1-positive myeloid cells (neutrophilia), severe anaemia and thrombocytosis, with reduced numbers of long-term haematopoietic stem cells (LT-HSCs), short-term haematopoietic stem cells (ST-HSCs) and multipotential progenitor cells (MPPs), increased circulating interleukin-6 (IL-6) and severe gastrointestinal inflammation. These findings identify distinct functions for the two IKK catalytic subunits, IKK1 and IKK2, in the haematopoietic system.

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