Mrtfa, also known as Megakaryoblastic Leukemia 1 (MKL1), is a coactivator of serum response factor (SRF). SRF participates in several critical cellular functions including cell growth and apoptosis. Mrtfa couples transcriptional regulation to actin cytoskeleton dynamics, and the Mrtfa-SRF complex targets genes encoding cytoskeletal proteins and immediate early genes. It promotes the differentiation of many cell types, such as muscle and hematopoietic cells, and its interactions with other proteins broaden its cellular roles [1].

In primary hematopoietic cells, knockout of Mrtfa decreases megakaryocyte (Mk) maturation causing thrombocytopenia, while Mrtfa overexpression in HEL cells enhances megakaryopoiesis. Mrtfa increases the genomic association and activity of SRF and upregulates genes that enhance primary human megakaryopoiesis [2]. In cardiomyocytes, Cypher/ZASP deficiency leads to destabilization of F-actin, increased G-actin levels, impeding Mrtfa nuclear localisation and SRF transcription, resulting in impaired cardiomyocyte maturation [3]. In human coronary artery smooth muscle cells, Mrtfa promotes lipid accumulation, and its inhibition reduces lipid accumulation [4]. In ERα positive breast cancer cells, Mrtfa nuclear accumulation remodels ERα location and functions, shifting its activity from nuclear genome regulation to extra-nuclear non-genomic signaling [5]. In disseminated cancer cells, Mrtf activation by pericyte-like spreading is critical for metastatic colonization [6]. Genetic disruption of Mrtf-SRF interaction or an Mrtf/SRF inhibitor impacts quiescent ovarian cancer cell gene expression and induces quiescence in various cancer cells [7]. Knockdown of WAVE2 in myoblasts reduces filamentous actin levels, increases globular actin, impairs Mrtfa nuclear translocation, and suppresses myogenic differentiation [8].

In conclusion, Mrtfa plays essential roles in cell differentiation, hematopoiesis, lipid homeostasis, and cancer-related processes. Gene knockout and other functional studies in various models, especially in cells related to specific diseases like megakaryoblastic leukemia, cardiomyopathy, and cancer, have revealed its importance in these biological functions and disease conditions, providing potential therapeutic targets.