The MicroBar project has made significant advances both methodology and biological understanding of hematopoiesis. The team successfully achieved its main goals: developing new tools for lineage tracing in humans, advancing the study of blood cell formation in mice and human. These efforts have yielded significant scientific discoveries and produced tools that are now available for wider use in research and clinical applications.
The first major goal of the project was to develop a new technological pipeline for single-cell lineage (SCLin) tracing in humans. Initially, we explored using microsatellite data for lineage tracing, but the approach encountered significant limitations due to high levels of missing data. This led to the publication of a methodological paper that outlined these challenges and prompted a shift in strategy. We then focused on using mitochondrial mutations as an alternative approach for lineage tracing. This led to the development of the first statistical method for identifying lineage-informative mitochondrial mutations from single-cell data.
The second major goal was to apply SCLin methods to study blood cell development in mice.
A breakthrough came with the creation of the DRAG mouse model, a genetically modified system that generates lineage barcodes through recombination of artificial gene segments. This allowed us to perform lineage tracing without the need for lentiviral infection or transplantation. Using this system, we uncovered key insights into how hematopoietic stem cells function during aging. Contrary to the long-held belief that stem cells become exhausted with age, we found that in their native environment, older stem cells continue to contribute to blood production without showing signs of functional decline.
Additionally, we identified a critical link between hematopoietic stem cell metabolism and their lineage specification. We discovered that hematopoietic stem cells undergo metabolic changes to support myelopoiesis (the production of some white blood cells), with the pentose phosphate pathway playing a pivotal role in this process. This finding opens potential avenues for using metabolic interventions to influence immune cell production.
The third objective focused on applying the lineage-tracing techniques developed in the project to human samples. Using human bone marrow and cord blood, we successfully traced cell lineages and are currently finalizing our analysis to uncovered new insights into human hematopoiesis.
The results of the MicroBar project have been disseminated through numerous publications in peer reviewed scientific journals, including Nature Genetics, Nature Communications, Blood, and IEEE/ACM, as well as several conference presentations. Several computational tools and bioinformatics pipelines developed during the project have been made available to the wider research community as open access. These include software packages that facilitate the analysis of single-cell lineage data and the identification of lineage-informative mitochondrial mutations.
The innovative methodologies developed through MicroBar have broad applications in both basic and clinical research. The lineage-tracing techniques can be used to study stem cell behavior in various contexts, including normal development and disease progression, and are particularly relevant for understanding diseases like leukemia. The project’s findings and resources are now available for further research, and the tools we developed will continue to be used in future studies to explore hematopoiesis and other stem cell-related processes.
