Clonal hematopoiesis in human aging and disease Jaiswal, Siddhartha; Ebert, Benjamin L
Science (American Association for the Advancement of Science),
11/2019, Letnik:
366, Številka:
6465
Journal Article
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As people age, their tissues accumulate an increasing number of somatic mutations. Although most of these mutations are of little or no functional consequence, a mutation may arise that confers a ...fitness advantage on a cell. When this process happens in the hematopoietic system, a substantial proportion of circulating blood cells may derive from a single mutated stem cell. This outgrowth, called "clonal hematopoiesis," is highly prevalent in the elderly population. Here we discuss recent advances in our knowledge of clonal hematopoiesis, its relationship to malignancies, its link to nonmalignant diseases of aging, and its potential impact on immune function. Clonal hematopoiesis provides a glimpse into the process of mutation and selection that likely occurs in all somatic tissues.
Ribosomopathies compose a collection of disorders in which genetic abnormalities cause impaired ribosome biogenesis and function, resulting in specific clinical phenotypes. Congenital mutations in ...RPS19 and other genes encoding ribosomal proteins cause Diamond-Blackfan anemia, a disorder characterized by hypoplastic, macrocytic anemia. Mutations in other genes required for normal ribosome biogenesis have been implicated in other rare congenital syndromes, Schwachman-Diamond syndrome, dyskeratosis congenita, cartilage hair hypoplasia, and Treacher Collins syndrome. In addition, the 5q− syndrome, a subtype of myelodysplastic syndrome, is caused by a somatically acquired deletion of chromosome 5q, which leads to haploinsufficiency of the ribosomal protein RPS14 and an erythroid phenotype highly similar to Diamond-Blackfan anemia. Acquired abnormalities in ribosome function have been implicated more broadly in human malignancies. The p53 pathway provides a surveillance mechanism for protein translation as well as genome integrity and is activated by defects in ribosome biogenesis; this pathway appears to be a critical mediator of many of the clinical features of ribosomopathies. Elucidation of the mechanisms whereby selective abnormalities in ribosome biogenesis cause specific clinical syndromes will hopefully lead to novel therapeutic strategies for these diseases.
Mesenchymal stem cells (MSCs) reside in the perivascular niche of many organs, including kidney, lung, liver, and heart, although their roles in these tissues are poorly understood. Here, we ...demonstrate that Gli1 marks perivascular MSC-like cells that substantially contribute to organ fibrosis. In vitro, Gli1+ cells express typical MSC markers, exhibit trilineage differentiation capacity, and possess colony-forming activity, despite constituting a small fraction of the platelet-derived growth factor-β (PDGFRβ)+ cell population. Genetic lineage tracing analysis demonstrates that tissue-resident, but not circulating, Gli1+ cells proliferate after kidney, lung, liver, or heart injury to generate myofibroblasts. Genetic ablation of these cells substantially ameliorates kidney and heart fibrosis and preserves ejection fraction in a model of induced heart failure. These findings implicate perivascular Gli1+ MSC-like cells as a major cellular origin of organ fibrosis and demonstrate that these cells may be a relevant therapeutic target to prevent solid organ dysfunction after injury.
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•Gli1 marks a perivascular network of MSC-like cells across major organs•Gli1+ cells are a CFU-F enriched fraction of the interstitial PDGFRβ+ population•Upon organ injury resident Gli1+ cells expand and become myofibroblasts•Genetic ablation of Gli1+ cells ameliorates fibrosis and rescues organ function
The cellular origins of fibrosis in different tissues are unclear. Kramann et al. show that Gli1 marks a network of perivascular mesenchymal-stem-cell-like cells that generate myofibroblasts and play a central role in organ fibrosis after injury, and ablating these cells ameliorates fibrosis and rescues organ function.
Myelodysplastic syndrome (MDS) is clonal disorder characterized by ineffective hematopoiesis and a tendency to evolve into acute myeloid leukemia (AML). Genetic studies have enabled the ...identification of a set of recurrently mutated genes central to the pathogenesis of MDS, which can be organized into a limited number of cellular processes, including RNA splicing, epigenetic and traditional transcriptional regulation, and signal transduction. The sequential accumulation of mutations drives disease evolution from asymptomatic clonal hematopoiesis to frank MDS, and, ultimately, to secondary AML. This detailed understanding of the molecular landscape of MDS, coupled with the emergence of cost- and time-effective methodologies for DNA sequencing has led to the introduction of genetic studies into the clinical realm. Here, we review recent advances in our genetic understanding of MDS, with a particular focus on the emerging role for mutational data in clinical management as a potential tool to assist in diagnosis, risk stratification, and therapeutic decision-making.
The 2010 and 2017 editions of the European LeukemiaNet (ELN) recommendations for diagnosis and management of acute myeloid leukemia (AML) in adults are widely recognized among physicians and ...investigators. There have been major advances in our understanding of AML, including new knowledge about the molecular pathogenesis of AML, leading to an update of the disease classification, technological progress in genomic diagnostics and assessment of measurable residual disease, and the successful development of new therapeutic agents, such as FLT3, IDH1, IDH2, and BCL2 inhibitors. These advances have prompted this update that includes a revised ELN genetic risk classification, revised response criteria, and treatment recommendations.
Lenalidomide acts by a novel drug mechanism—modulation of the substrate specificity of the CRL4CRBN E3 ubiquitin ligase. In multiple myeloma, lenalidomide induces the ubiquitination of IKZF1 and ...IKZF3 by CRL4CRBN. Subsequent proteasomal degradation of these transcription factors kills multiple myeloma cells. In del(5q) myelodysplastic syndrome, lenalidomide induces the degradation of CK1α, which preferentially affects del(5q) cells because they express this gene at haploinsufficient levels. In the future, modulation of ubiquitin ligase function may enable us to target previously “undruggable” proteins.
Recent genetic analyses of large populations have revealed that somatic mutations in hematopoietic cells leading to clonal expansion are commonly acquired during human aging. Clonally restricted ...hematopoiesis is associated with an increased risk of subsequent diagnosis of myeloid or lymphoid neoplasia and increased all-cause mortality. Although myelodysplastic syndromes (MDS) are defined by cytopenias, dysplastic morphology of blood and marrow cells, and clonal hematopoiesis, most individuals who acquire clonal hematopoiesis during aging will never develop MDS. Therefore, acquisition of somatic mutations that drive clonal expansion in the absence of cytopenias and dysplastic hematopoiesis can be considered clonal hematopoiesis of indeterminate potential (CHIP), analogous to monoclonal gammopathy of undetermined significance and monoclonal B-cell lymphocytosis, which are precursor states for hematologic neoplasms but are usually benign and do not progress. Because mutations are frequently observed in healthy older persons, detection of an MDS-associated somatic mutation in a cytopenic patient without other evidence of MDS may cause diagnostic uncertainty. Here we discuss the nature and prevalence of CHIP, distinction of this state from MDS, and current areas of uncertainty regarding diagnostic criteria for myeloid malignancies.
Myelodysplastic syndrome (MDS) is a clonal disease that arises from the expansion of mutated haematopoietic stem cells. In a spectrum of myeloid disorders ranging from clonal haematopoiesis of ...indeterminate potential (CHIP) to secondary acute myeloid leukaemia (sAML), MDS is distinguished by the presence of peripheral blood cytopenias, dysplastic haematopoietic differentiation and the absence of features that define acute leukaemia. More than 50 recurrently mutated genes are involved in the pathogenesis of MDS, including genes that encode proteins involved in pre-mRNA splicing, epigenetic regulation and transcription. In this Review we discuss the molecular processes that lead to CHIP and further clonal evolution to MDS and sAML. We also highlight the ways in which these insights are shaping the clinical management of MDS, including classification schemata, prognostic scoring systems and therapeutic approaches.
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