LIM domain only 2 (rhombotin-like 1), also known as LMO2, RBTNL1, RBTN2, RHOM2, LIM Domain Only Protein 2, TTG2, and T-Cell Translocation Protein 2, is a protein which in humans is encoded by the LMO2 gene. LMO2 encodes a cysteine-rich, two LIM domain protein that is required for yolk sac erythropoiesis.The LMO2 protein has a central and crucial role in hematopoietic development and is highly conserved. Aberrant LMO2 expression is a significant feature of T cell acute lymphoblastic leukaemia with multiple described mechanisms of activation.