Distinct Notch1 and BCL11B requirements mediate human γδ/αβ T cell development [BCL11B_coculture]

Notch-dependent BCL11B induction converts thymus seeding precursor cells into committed T cell progenitors that subsequently differentiate into T cells bearing either the γδ or αβ T cell receptor. In human, strong Notch activation favors γδ T cell development at the expense of αβ-lineage differentiation, but the underlying molecular mechanism has remained unclear. Therefore, we performed paired mRNA and miRNA profiling across 11 stages of human T cell development, including developing γδ T cells. We identify the miR-17-92 cluster as a direct Notch target and show that miR-17 promotes human TCRγδ T cell development by targeting BCL11B, a gene required for αβ but not for γδ T cell development. Thus, following its role as a licensing factor to induce BCL11B expression in early T cell precursors, Notch activation limits BCL11B expression through miR-17 until thymocytes have passed the β-selection checkpoint when Notch activation is turned off. Hereby Notch prevents premature BCL11B upregulation that is required for αβ-lineage differentiation and this results in preferential γδ-lineage differentiation. Our work unravels a dual role for Notch in controlling BCL11B expression during intrathymic differentiation and provides a unique resource for understanding the mRNA/miRNA interactions that control human T cell development. We used microarrays in order to profile gene expression in CD34+ thymocytes before culture and after 5 or 10 days culture on OP9 stromal cells expressing Notch ligands JAG1, JAG2, DLL1 or DLL4. Gene expression was profiled in CD34+ thymocytes before and after culture on OP9 stromal cells expressing JAG1, JAG2, DLL1 or DLL4. Cultured cells were harvested after 5 days or 10 days of culture and sorted for CD45+. 2 independent experiments were performed, using 2 different thymus donors (2 replicates for each experimental setup).