Abstract

Foxp3+ regulatory T-cells (Treg) are considered to mainly differentiate in the thymus and protect against autoimmunity. However, the physiological significance of peripheral Treg differentiation is still unclear, due to a lack of methods to identify newly formed cells in vivo. In addition, the mechanism of Treg generation in the thymus is still obscure, because of difficulties in defining temporal sequences of developmental events in vivo.

In order to solve these problems, recently we have established a ground-breaking approach using Fluorescent Timer protein that spontaneously and irreversibly changes its emission spectrum. We have developed novel Timer reporters using key genes for T-cell functions, and validated the new reporter systems by in silico, in vitro, and in vivo experiments. By developing Foxp3Timer reporter, we reveal the mechanisms of dynamic Treg differentiation processes in the thymus and in the periphery. In addition, by developing a novel Timer reporter for a TCR -downstream immediate early gene, we establish a TCR -responsive Timer reporter system, and thereby reveal temporal sequences of T-cell differentiation events upon TCR signalling in vivo.