MYSM1, a deubiquitinating enzyme, is a crucial regulator in diverse biological processes. It belongs to the metalloprotease family and has SANT and SWIRM domains. MYSM1 can localize to the nucleus, where it regulates gene expression by deubiquitinating histone H2A and interacting with other transcriptional regulators, and also has a cytosolic form that modulates innate immunity signal transduction pathways [2]. It is involved in stem cell function, immune responses, and is associated with the pathogenesis of various diseases [1]. The high sequence homology between murine and human MYSM1, along with similar phenotypes in Mysm1 -deficient models, makes mouse models valuable for studying human Mysm1 -deficiency syndromes [1].

In Mysm1 -deficient mice, there are abnormal developments across multiple tissues and organs. For example, Mysm1 knockdown in mice by crossing Mysm1 floxed mice with Nestin-Cre mice led to abnormal brain development with microcephaly, as Mysm1 deletion promoted neural stem cell (NSC) proliferation and apoptosis, depleting the stem cell pool, and skewing NSCs towards neurogenesis instead of astrogliogenesis [3]. In the hematopoietic system, loss of MYSM1 in a bone marrow failure disorder led to selectively disadvantaged hematopoietic stem cells (HSCs), with reduced protein synthesis in HSCs resulting in increased ferroptosis [5]. Genetic knockdown of MYSM1 significantly mitigated doxorubicin-induced cardiomyopathy, and cardiomyocyte-specific knockdown protected the heart from doxorubicin-induced cardiotoxicity [4]. Mysm1 -deficient mice also exhibit a hyper-inflammatory response, acute tissue damage, and high mortality upon virus infection due to the loss of MYSM1's suppression of the cGAS-STING pathway [6].

In conclusion, MYSM1 is an important regulator in multiple biological processes, including stem cell function, immunity, and tissue development. Mysm1 knockout or conditional knockout mouse models have revealed its roles in various disease conditions such as neurodevelopmental disorders, hematopoietic disorders, cardiotoxicity, and immune-related diseases. These findings provide valuable insights into the etiology of human Mysm1-deficiency syndromes and suggest MYSM1 as a potential therapeutic target in related diseases.