TGFβ determines morphology and key cellular processes of activated CD4+ T cells
During an immune response, cells are simultaneously exposed to multiple cytokine signals that collectively determine their phenotype. Transforming growth factor {beta} (TGF{beta}) is a pleiotropic cytokine acting as a key regulator of T-cell differentiation with activating and suppressive effects on their immune function. Here, we systematically analyze the cellular responses of CD4+ T cells to TGF{beta} across diverse cytokine environments in the presence or absence of TGF{beta}. We found that TGF{beta} had a profound dominant effect independent of the presence of other cytokines, modulating the expression of more than 4,000 genes. In the presence of TGF{beta}, cells exhibit lower expression of translation-related and apoptosis-related genes, accompanied by increased survival of activated T cells. Notably, cells cultured in the presence of TGF{beta} were smaller in size while preserving their proliferative ability. Accordingly, we identified a dense network of transcription factors that were modulated by TGF{beta}, suggesting a core gene set connecting TGF{beta} signaling to the regulation of T-cell size. We found N-Myc to be at the center of this network, and we directly show that TGF{beta} regulates its gene expression level, protein level, and nuclear localization. Our work provides a system to study cell size control and demonstrate the profound effect of TGF{beta} in the modulation and regulation of T-cell properties, expanding its role beyond guiding their phenotype. Significance StatementTGF{beta} is a key determinant of CD4+ T-cell differentiation; however, understanding its effect on additional aspects of T-cell state is lacking. Here, we systematically studied the role of TGF{beta} in regulating T-cell physiology. Exposing cells to diverse combinations of cytokines enabled us to distill the core effect of TGF{beta}. We found TGF{beta} to have a profound effect on multiple cellular processes critical to T-cell function. Significantly, TGF{beta} induced smaller T-cells both in vitro and in vivo, suggesting that TGF{beta} could skew the population towards tissue infiltration and residency. Furthermore, TGF{beta} can be used to fine-tune T-cell size, providing a system for studying cell size control. Overall, our findings demonstrate the profound effect of TGF{beta} in the regulation of T-cell physiology.