Dynamic changes of nonepithelial thymic stroma during thymus organogenesis

The thymic stroma provides the microenvironment for T cell lineage commitment, development, maturation, and repertoire selection. While the thymic epithelial cell (TEC) compartment is relatively well characterised, a comparably detailed analysis of the non-TEC stromal compartment including the endothelial cells and fibroblasts is currently lacking. Here, we probe the composition of thymic mesenchymal cells and their dynamic change during thymus organogenesis. Using a single cell transcriptomic approach, we identify previously unappreciated heterogeneity within the non-TEC stromal compartment and demonstrate dynamic shifts within non-TEC stromal cell populations over thymic development. We then use a compound heterozygous model (Tbx1+/-Crkl+/-) for 22q11.2DS syndrome to show that significant reductions of multiple mesenchymal subpopulations associated with functional defects and accelerated aging are associated with the thymic hypoplasia observed in this condition. Thus, we provided a comprehensive picture of non-TEC thymic stromal development and their functional defects in a disease model of thymic hypoplasia. Overall design: Thymic stromal cells - 10X gene expression: non-TEC thymic stroma over development (n=8) and thymic stroma wild-type vs. Tbx1+/-Crkl+/- mice (n=6); RNA-seq wild-type thymic stroma mice