MiR-125a Is a critical modulator for neutrophil development

MicroRNAs are universal post-transcriptional regulators in genomes. They have the ability of buffering gene expressional programs, contributing to robustness of biological systems and playing important roles in development, physiology and diseases. Here, we identified a microRNA, miR-125a, as a positive regulator of granulopoiesis. MiR125a knockout mice show reduced infiltration of neutrophils in the lung and alleviated tissue destruction after endotoxin challenge as a consequence of decreased neutrophil numbers. Furthermore, we demonstrated that this significant reduction of neutrophils was due to impaired development of granulocyte precursors to mature neutrophils in an intrinsic manner. We showed that Socs3, a critical repressor for granulopoiesis, was a target of miR-125a. Overall, our study revealed a new microRNA regulating granulocyte development and supported a model in which miR-125a acted as a fine-tuner of granulopoiesis.
Author summary MicroRNAs are critical epigenetic modulators in development, physiology and disease processes. Many miRNAs are involved in immune cell development and function, like miR-150 for B cells, miR-181a for T cells. However, studies of miRNAs involvement in granulocyte development and function and related diseases are still limited. In this study, we developed engineering MiR125a knockout mice to study the function of miR-125a in vivo. We identified MiR125a knockout mice had decreased neutrophil numbers and reduced infiltration of neutrophils in the lung in LPS shock model. We deduced that this significant reduction of neutrophils was due to impaired development of granulocyte precursors to mature neutrophils in an intrinsic manner. Furthermore, we demonstrated that Socs3, a major repressor that negatively regulates granulocyte development, was a target of miR-125a. This finding not only reveals a new microRNA involving granulocyte development, but also provides insights into the new mechanism of miR-125a during action in endotoxemia.