Mouse CD4+/CD8+ thymocytes from miR-181a1/b1 KO vs WT. Mus musculus

miR-181a1/b1, miR-181a2/b2, and miR-181c/d belong to a highly conserved family of microRNA clusters, yet their role in vivo is poorly understood. Here we show that the miR-181a1/b1 cluster is absolutely essential for NKT development and is a critical determinant of thymocyte proliferation, survival and T-cell receptor α locus rearrangement. Furthermore, while individual ablation of miR-181a2/b2 and miR-181c/d revealed no overt phenotypes, compound mutant mice lacking both miR-181a1/b1 and miR-181a2/b2 display decreased survival, reduced body weight, and abnormal B cell development. Mechanistically, we reveal that miR-181 regulates PTEN, a key tumor suppressor whose abundance determines key metabolic adaptations required to meet the biosynthetic demands of highly proliferative tissues. These results provide important insights into the physiological function of this family of microRNAs in vivo; moreover, it places miR-181 as a central regulator of the PI3K signaling pathway and cellular metabolism. Overall design: Three sorted populations of double positive (DP) thymocytes from each of two conditions (WT and miR181a1/b1 -/- mice)