Selective advantage of mutant stem cells in human clonal hematopoiesis is associated with attenuated response to inflammation and aging.

Clonal hematopoiesis (CH) arises when hematopoietic stem cells (HSCs) acquire mutations, most frequently in the DNMT3A and TET2 genes, conferring a competitive advantage through mechanisms that remain unclear. To gain insight into how CH mutations enable gradual clonal expansion, we used single-cell multi-omics with high-fidelity genotyping on human CH bone marrow (BM) samples. Most of the selective advantage of mutant cells occurs within HSCs.

The Hematopoietic Bone Marrow Niche Ecosystem.

The bone marrow (BM) microenvironment, also called the BM niche, is essential for the maintenance of fully functional blood cell formation (hematopoiesis) throughout life. Under physiologic conditions the niche protects hematopoietic stem cells (HSCs) from sustained or overstimulation. Acute or chronic stress deregulates hematopoiesis and some of these alterations occur indirectly via the niche.

Enhanced differentiation of functional human T cells in NSGW41 mice with tissue-specific expression of human interleukin-7.

Humanized mouse models have become increasingly valuable tools to study human hematopoiesis and infectious diseases. However, human T-cell differentiation remains inefficient. We generated mice expressing human interleukin-7 (IL-7), a critical growth and survival factor for T cells, under the control of murine IL-7 regulatory elements.

Splicing factor YBX1 mediates persistence of JAK2-mutated neoplasms.

Janus kinases (JAKs) mediate responses to cytokines, hormones and growth factors in haematopoietic cells. The JAK gene JAK2 is frequently mutated in the ageing haematopoietic system and in haematopoietic cancers. JAK2 mutations constitutively activate downstream signalling and are drivers of myeloproliferative neoplasm (MPN).

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition).

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells.

Comparative RNAi Screens in Isogenic Human Stem Cells Reveal SMARCA4 as a Differential Regulator.

Large-scale RNAi screens are a powerful approach to identify functions of genes in a cell-type-specific manner. For model organisms, genetically identical (isogenic) cells from different cell types are readily available, making comparative studies meaningful. However, large-scale screens in isogenic human primary cells remain challenging.

Epigenetic aging of human hematopoietic cells is not accelerated upon transplantation into mice.

Background: Transplantation of human hematopoietic stem cells into immunodeficient mice provides a powerful in vivo model system to gain functional insights into hematopoietic differentiation. So far, it remains unclear if epigenetic changes of normal human hematopoiesis are recapitulated upon engraftment into such "humanized mice." Mice have a much shorter life expectancy than men, and therefore, we hypothesized that the xenogeneic environment might greatly accelerate the epigenetic clock.

Improved Human Erythropoiesis and Platelet Formation in Humanized NSGW41 Mice.

Human erythro-megakaryopoiesis does not occur in humanized mouse models, preventing the in vivo analysis of human hematopoietic stem cell (HSC) differentiation into these lineages in a surrogate host. Here we show that stably engrafted KIT-deficient NOD/SCID Il2rgKit (NSGW41) mice support much improved human erythropoiesis and platelet formation compared with irradiated NSG recipients. Considerable numbers of human erythroblasts and mature thrombocytes are present in the bone marrow and blood, respectively.

GSK3 Deficiencies in Hematopoietic Stem Cells Initiate Pre-neoplastic State that Is Predictive of Clinical Outcomes of Human Acute Leukemia.

Initial pathway alternations required for pathogenesis of human acute myeloid leukemia (AML) are poorly understood. Here we reveal that removal of glycogen synthase kinase-3α (GSK-3α) and GSK-3β dependency leads to aggressive AML. Although GSK-3α deletion alone has no effect, GSK-3β deletion in hematopoietic stem cells (HSCs) resulted in a pre-neoplastic state consistent with human myelodysplastic syndromes (MDSs).

Improved HSC reconstitution and protection from inflammatory stress and chemotherapy in mice lacking granzyme B.

The serine protease granzyme B (GzmB) is stored in the granules of cytotoxic T and NK cells and facilitates immune-mediated destruction of virus-infected cells. In this study, we use genetic tools to report novel roles for GzmB as an important regulator of hematopoietic stem cell (HSC) function in response to stress. HSCs lacking the GzmB gene show improved bone marrow (BM) reconstitution associated with increased HSC proliferation and mitochondrial activity.