Mef2d, short for myocyte enhancer factor 2D, is a key transcription factor in the development of skeletal, cardiac, and neural tissues [4]. It is involved in various biological processes such as embryonic development, nervous system regulation, muscle cell differentiation, and the development of B-and T-cells [4]. In the immune system, Mef2d has been found to potentiate type-2 immune responses and allergic lung inflammation by regulating GATA3-dependent type-2 lymphocyte differentiation [2].

In disease-related research, in B-progenitor acute lymphoblastic leukaemia (B-ALL), MEF2D rearrangements with genes like BCL9, CSF1R, etc. are associated with a distinct gene expression profile, immunophenotype, and poor outcome [1]. In hepatocellular carcinoma, MEF2D promotes the expression of PD-L1, preventing CD8+ T-cell-mediated antitumor immunity [3]. In gastric cancer, overexpressing MEF2D in mouse models promotes liver metastasis, while knockdown inhibits it [5]. In breast cancer, knockout of MEF2D in mouse mammary epithelial cells leads to neoplastic transformation, suggesting it may act as a tumor suppressor [6].

In conclusion, Mef2d is crucial for normal tissue development and immune responses. Its dysregulation is involved in multiple diseases including leukemia, liver and gastric cancers, and breast cancer. Gene knockout models in mice have been instrumental in revealing its role in these disease processes, providing insights for potential therapeutic strategies.