Unveiling differentiation trajectories of T lymphocytes with single cell resolution

• Applicant: Professor Dr. Dominic Grün
• Subject Area: Cell Biology ; Bioinformatics and Theoretical Biology
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 371991985

The emergence of the distinct blood lineages from hematopoietic stem cells in the bone marrow of mammalian organisms is an attractive model for adult stem cell differentiation. In particular, understanding hematopoietic cell fate decisions is prerequisite to the development of novel, targeted therapeutic treatments for blood and immune diseases.Decades of research have been dedicated to elucidate stem, progenitor, and mature cell types within the bone marrow and within lymphoid organs, such as thymus and spleen. From this research a hematopoietic lineage tree has emerged, that is sub-divided into discrete states characterized based on few cell surface markers. Recent studies employing single cell mRNA-sequencing and lineage-tracing utilizing cell barcoding have revealed substantial heterogeneity within progenitor populations previously considered homogenous.In this project, we will perform a high-resolution analysis of T lymphocyte differentiation comprising early progenitor stages in the bone marrow, i. e. common lymphoid progenitors, and subsequent differentiation stages within the thymus. To this end, we will apply single-cell-mRNA sequencing to thousands of cells covering all differentiation stages and simultaneously measure the expression of cell surface markers, traditionally used to define discrete differentiation stages, by flow cytometry. This permits a direct comparison of the de novo identified stages to the conventional differentiation stages defined based on cell surface markers and enables the discovery of previously hidden heterogeneity. With our recently published algorithms we will resolve sub-types on the differentiation trajectories of T lymphocytes and assemble these into a high-resolution lineage tree. With these data we will attempt to characterize T lineage progenitors in the bone marrow and to elucidate cell fate decisions and cell type plasticity within the thymus. We will utilize our findings for in-depth follow-up experiments.We anticipate that the results of the project presented here can substantially improve the understanding of T cell differentiation and provide the basis for investigating aberrant differentiation in diseases such as leukemia.

• DFG Programme: Research Grants