Transgenic expression of cyclin D1 in thymic epithelial precursors promotes epithelial and T cell development

We previously reported that precursors within the keratin (K) 8⁺5⁺ thymic epithelial cell (TEC) subset generate the major cortical K8⁺5^- TEC population in a process dependent on T lineage commitment. This report demonstrates that expression of a cyclin D1 transgene in K8⁺5⁺ TECs expands this subset and promotes TEC and thymocyte development. Cyclin D1 transgene expression is not sufficient to induce TEC differentiation in the absence of T lineage-committed thymocytes because TECs from both hCD3ε transgenic and hCD3ε/cyclin D1 double transgenic mice remain blocked at the K8⁺5⁺ maturation stage. However, enforced cyclin D1 expression does expand the developmental window during which K8⁺5⁺ cells can differentiate in response to normal hemopoietic precursors. Thus, enhancement of thymic function may be achieved by manipulating the growth and/or survival of TEC precursors within the K8⁺5⁺ subset.