Understanding hematopoiesis from a single-cell standpoint.

The cellular diversity of the hematopoietic system has been extensively studied, and a plethora of cell surface markers have been used to discriminate and prospectively purify different blood cell types. However, even within phenotypically identical fractions of hematopoietic stem and progenitor cells or lineage-restricted progenitors, significant functional heterogeneity is observed when single cells are analyzed. To address these challenges, researchers are now using techniques to follow single cells and their progeny to improve our understanding of the underlying functional heterogeneity. On November 19, 2015, Dr. David Kent and Dr. Leïla Perié, two emerging young group leaders, presented their recent efforts to dissect the functional properties of individual cells with a webinar series organized by the International Society for Experimental Hematology. Here, we provide a summary of the presented methods for cell labeling and clonal tracking and discuss how these different techniques have been employed to study hematopoiesis.MRC, Wellcome-Trust, BloodwiseThis is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.exphem.2016.03.00

A track of the clones: new developments in cellular barcoding.

International experts from multiple disciplines gathered at Homerton College in Cambridge, UK from September 12-14, 2018 to consider recent advances and emerging opportunities in the clonal tracking of hematopoiesis in one of a series of StemCellMathLab workshops. The group included 35 participants with experience in the fields of theoretical and experimental aspects of clonal tracking, and ranged from doctoral students to senior professors. Data from a variety of model systems and from clinical gene therapy trials were discussed, along with strategies for data analysis and sharing and challenges arising due to underlying assumptions in data interpretation and communication. Recognizing the power of this technology underpinned a group consensus of a need for improved mechanisms for sharing data and analytical protocols to maintain reproducibility and rigor in its application to complex tissues.We thank the BBSRC (BB/R021465/1), the German Stem Cell Network, the Wellcome-MRC Cambridge Stem Cell Institute and the Labex CelTisPhyBio (No. ANR-10-LBX-0038) for funds to support this workshop and the conference staff at Homerton Colleg

To portray clonal evolution in blood cancer, count your stem cells

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En quête de métaphores, une proposition méthodologique. Le cas des sols agricoles

International audienceWe present a method for identifying the various metaphors used in a scientific field, and seeing how they can best serve research and its applications. Starting with the metaphors used to talk about agricultural soils, we created this method to facilitate understanding and the formulation of responses that are up to the social and ecological issues at stake. As each metaphor sheds a singular light on the issue under study, but leaves other aspects "in the dark" too, it is crucial to study and use a plurality of metaphors. The method consists in: revealing a diversity of metaphors; organizing them into sets; specifying and questioning the elements of understanding provided by each set, but also its limits; completing these insights by questioning specialists on the subject. The result allows to lively knowledge and perceptions sharing, open to dialogue between science and society, which in the case of soils offers new ways of considering and studying them in order to better counter their degradation.Nous présentons une méthode pour relever les différentes métaphores utilisées dans un domaine scientifique, et voir comment elles peuvent servir au mieux la recherche et ses applications. Prenant comme point de départ les métaphores utilisées pour parler des sols agricoles, nous avons élaboré cette méthode d’enquête métaphorique pour accompagner la compréhension et la formulation de réponses à la hauteur des enjeux sociaux et écologiques autour des sols agricoles. Comme chaque métaphore apporte un éclairage singulier sur la question étudiée, mais laisse d’autres aspects « dans l’ombre », il apparaît essentiel d’étudier et d’utiliser les métaphores dans leur pluralité. La méthode consiste : à révéler une diversité de métaphores ; à les organiser par ensembles ; à préciser et questionner les éléments de compréhension apportés par chaque ensemble, mais également ses limites ; à compléter ces éclairages en interrogeant les spécialistes du sujet. Il en résulte un partage vivant des connaissances et des représentations, ouvert au dialogue entre sciences et société, qui dans le cas des sols offre de nouvelles façons de les considérer et les étudier afin de mieux contrer leur dégradation

CellDestiny: A RShiny application for the visualization and analysis of single-cell lineage tracing data

International audienceSingle-cell lineage tracing permits the labeling of individual cells with a heritable marker to follow the fate of each cell's progeny. Over the last twenty years, several single-cell lineage tracing methods have emerged, enabling major discoveries in developmental biology, oncology and gene therapies. Analytical tools are needed to draw meaningful conclusions from lineage tracing measurements, which are characterized by high variability, sparsity and technical noise. However, the single cell lineage tracing field lacks versatile and easy-to-use tools for standardized and reproducible analyses, in particular tools accessible to biologists. Here we present CellDestiny, a RShiny app and associated web application developed for experimentalists without coding skills to perform visualization and analysis of single cell lineage-tracing datasets through a graphical user interface. We demonstrate the functionality of CellDestiny through the analysis of (i) lentiviral barcoding datasets of murine hematopoietic progenitors; (ii) published integration site data from Wiskott-Aldrich Symdrome patients undergoing gene-therapy treatment; and (iii) simultaneous barcoding and transcriptomic analysis of murine hematopoietic progenitor differentiation in vitro. In summary, CellDestiny is an easy-to-use and versatile toolkit that enables biologists to visualize and analyze single-cell lineage tracing data

Hematopoiesis in numbers

Hematopoiesis is a dynamic process in which stem and progenitor cells give rise to the ~10 13 blood and immune cells distributed throughout the human body. We argue that a quantitative description of hematopoiesis can help consolidate existing data, identify knowledge gaps, and generate new hypotheses. Here, we review known numbers in murine and, where possible, human hematopoiesis, and consolidate murine numbers into a set of reference values. We present estimates of cell numbers, division and differentiation rates, cell size, and macromolecular composition for each hematopoietic cell type. We also propose guidelines to improve the reporting of measurements and highlight areas in which quantitative data are lacking. Overall, we show how quantitative approaches can be used to understand key properties of hematopoiesis

The Branching Point in Erythro-Myeloid Differentiation

Development of mature blood cell progenies from hematopoietic stem cells involves the transition through lineage-restricted progenitors. The first branching point along this developmental process is thought to separate the erythro-myeloid and lymphoid lineage fate by yielding two intermediate progenitors, the common myeloid and the common lymphoid progenitors (CMPs and CLPs). Here, we use single-cell lineage tracing to demonstrate that so-called CMPs are highly heterogeneous with respect to cellular output, with most individual CMPs yielding either only erythrocytes or only myeloid cells after transplantation. Furthermore, based on the labeling of earlier progenitors, we show that the divergence between the myeloid and erythroid lineage develops within multipotent progenitors (MPP). These data provide evidence for a model of hematopoietic branching in which multiple distinct lineage commitments occur in parallel within the MPP pool

A track of the clones: new developments in cellular barcoding

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