Biology subjects

Thielecke, L.

Publications and source records attributed to Thielecke, L..

5 recordsLinked to original sources

bioRxiv2025

Long-term clonal analysis using stochastic models reveals heterogeneity and quiescence of hematopoietic stem cells

Hematopoietic stem cells (HSCs) maintain lifelong production of blood by balancing self-renewal and differentiation. However, certain aspects of their divisional dynamics, namely the role of quiescence and the intrinsic heterogeneity of the HSC pool, are not completely understood. High-resolution clonal tracking provides a powerful resource to investigate such dynamics as the data captures patterns of clonal persistence, dilution and late clonal emergence. Here, we apply mechanistic mathematical modeling to longitudinal clonal data from non-human primates to explore structural requirements that underlie the observed dynamical patterns. We show that models treating HSCs as a single, homogeneous population can explain the gradual loss of clonal diversity, but fail to reproduce clone size distributions and the long-term persistence of small and late-appearing clones. To address this, we propose a stochastic, two-compartment model in which HSCs transition reversibly between an actively cycling state and a quiescent, potentially niche-bound state. Compared to the simpler one-compartment model, this advanced framework provides a substantially improved fit for different metrics, consistently captures clone size distributions and explains the delayed activation and sustained coexistence of small and large clones. These results provide quantitative evidence that heterogeneity within the HSC pool, particularly the existence of a reversible quiescent state, is critical to account for clonal aspects of long-term hematopoiesis. Our findings highlight how clonal data can uncover underlying regulatory mechanisms and supports a central role for niche-mediated HSC quiescence in maintaining stable and diverse blood production over time. HighlightsO_LIClonal data offers a robust approach to explore hematopoietic stem cell dynamics C_LIO_LIHomogeneous HSC population cannot reproduce observed long-term clonal patterns C_LIO_LINiche-mediated quiescence improves model fit across different clonality metrics C_LIO_LIModel results suggest reversible transition between HSC quiescence and activation C_LI

bioinformatics↗

bioRxiv2020

Age-independent influence of hematopoietic stem and progenitor cell populations during hematopoietic reconstitution

Hematopoietic stem cell transplantation (HSCT) following myeloablative conditioning represents the only curative treatment option to overcome numerous hematologic malignancies. Despite the overall clinical success to achieve reconstitution of the blood system in many patients, the length of the aplastic phase until recovery response remains a critical parameter for patient survival. Fatal infections are the major risk factor for immunocompromised individuals and in many cases lead to transplant related morbidity and mortality. Therefore, we hypothesized that transplants from young donors might be beneficial for the spatiotemporal blood reconstitution in comparison to old grafts. Here we report on our multicolor-coded barcode system (BC32) to track hematopoietic stem and progenitor cell (HSPC) populations in a murine model of HSCT. By using different experimental settings of young and aged donor and recipient animals we compared the influence of age on graft composition, leukocyte recovery and more precisely, the contribution of individual HSPC subpopulations to the process. We show that blood reconstitution is substantially driven and maintained by HSCs and MPPs, while the latter accounted for higher output rates than HSCs, confirmed by FACS and NGS analyses. Reconstitution patterns were highly polyclonal and stable in all animals aside from variability between individual animals. This leads to the conclusion that HSPCs home, engraft and differentiate independently of donor and recipient age in our experimental conditions. Our findings add to ongoing efforts to expand the application of HSCT in older individuals while minimizing therapy related risks resulting from intensive myeloablative conditioning or incomplete blood reconstitution.

cell biology↗

bioRxiv2019

genBaRcode - a comprehensive R package for genetic barcode analysis

MotivationGenetic barcodes have been established as an efficient method to trace clonal progeny of uniquely labeled cells by introducing artificial genetic sequences into the corresponding genomes. The assessment of those sequences, relies on next generation sequencing and the subsequent analysis aiming to identify sequences of interest and correctly quantifying their abundance.\n\nResultsWe developed the genBaRcode package as a toolbox combining the flexibility of digesting next generation sequencing reads with or without a sophisticated barcode structure, with a variety of error correction approaches and the availability of several types of visualization routines. Furthermore, a graphical user interface was incorporated to allow also less experienced R users package-based analyses. Finally, the provided tool is intended to bridge the gap between generating and analyzing barcode data and thereby supporting the establishment of standardized and reproducible analysis strategies.\n\nAvailabilityThe genBaRcode package is available at CRAN (https://cran.r-project.org/pack-age=genBaRcode).\n\nContactlars.thielecke@tu-dresden.de

bioinformatics↗

bioRxiv2018

Engrafted parenchymal brain macrophages differ from host microglia in transcriptome, epigenome and responsiveness to challenge

Microglia are yolk sac-derived macrophages residing in the parenchyma of brain and spinal cord, where they interact with neurons and other glial cells by constantly probing their surroundings with dynamic extensions. Following different conditioning paradigms and bone marrow (BM) / hematopoietic stem cell (HSC) transplantation, graft-derived cells seed the brain and persistently contribute to the parenchymal brain macrophage compartment. Here we establish that these cells acquire over time microglia characteristics, including ramified morphology, longevity, radio-resistance and clonal expansion. However, even following prolonged CNS residence, transcriptomes and epigenomes of engrafted HSC-derived macrophages remain distinct from yolk sac-derived host microglia. Furthermore, BM graft-derived cells display discrete responses to peripheral endotoxin challenge, as compared to host microglia. Also in human HSC transplant recipients, engrafted cells remain distinct from host microglia, extending our finding to clinical settings. Collectively, our data emphasize the molecular and functional heterogeneity of parenchymal brain macrophages and highlight potential clinical implications for patients treated by HSC gene therapy.

immunology↗

bioRxiv2018

Hematopoietic stem cells differentiate into restricted myeloid progenitors before cell division

Hematopoietic stem cells (HSCs) continuously replenish all blood cell types through a series of differentiation steps that involve the generation of lineage-committed progenitors as well as necessary expansion due to repeated cell divisions. However, whether cell division in HSCs precedes differentiation is unclear. To this end, we used an HSC cell tracing approach and Ki67RFP knock-in mice to assess simultaneously divisional history, cell cycle progression, and differentiation of adult HSCs in vivo. Our results reveal that HSCs are able to differentiate into restricted progenitors, especially common myeloid progenitors, restricted megakaryocyte-erythroid progenitors (PreMEs) and pre-megakaryocyte progenitors (PreMegs), without undergoing cell division and even before entering the S phase of the cell cycle. Additionally, the phenotype of the undivided but differentiated progenitors correlated with expression of lineage-specific genes that manifested as functional differences between HSCs and restricted progenitors. Thus, HSC fate decisions appear to be uncoupled from physical cell division. Our results facilitate a better understanding of the mechanisms that control fate decisions in hematopoietic cells. Our data, together with separate findings from embryonic stem cells, suggest that cell division and fate choice are independent processes in pluripotent and multipotent stem cells.

cell biology↗