Micro RNA regulation of T‐cell development

Summary Micro RNA s are short, 19–24 nucleotide long, RNA molecules capable of regulating the longevity and, to a lesser extent, translation of messenger RNA (m RNA ) species. The function of the micro RNA network, and indeed, even that of individual micro RNA species, can have profoundly different roles in even a single cell type as the micro RNA /m RNA composition evolves. As the role of micro RNA within T cells has come under increasing scrutiny, several distinct checkpoints have been demonstrated to have a particular reliance on micro RNA regulation. Micro RNA s are arguably most important in T cells during the earliest and last stages in T‐cell biology. The first stages of early thymic differentiation have a crucial reliance on the micro RNA network, while later stages and peripheral homeostasis are largely, although not completely, micro RNA ‐independent. The most profound effects on T cells are in the activation of effector and regulatory functions of conventional and regulatory T cells, where micro RNA deficiency results in a near‐complete loss of function. In this review, we focus on integrating the research on individual micro RNA into a more global understanding of the function of the micro RNA regulatory network in T cells.