Msn, short for moesin, is a member of the ezrin-radixin-moesin family. It connects the cell membrane to the actin-based cytoskeleton, regulating cell morphology. It is also involved in various cellular processes and associated with multiple signaling pathways such as β-catenin-RUNX2 axis and PKC-CREB signaling [2,3].

In immunodeficiency, a novel hemizygous mutation (c.68 A > G, p.N23S) in the MSN gene was found in a patient presenting with recurrent fever, oral ulcers, dermatomyositis-like symptoms, EBV infection, and eventually developing nasal-type NK/T-cell lymphoma. The patient had attenuated MSN protein expression, impaired T-cell proliferation and migration [1]. In two brothers with repeated lung infections, a hemizygous missense mutation (c.511C > T:p.R171W) in exon 5 of the MSN gene was detected, which is an X-linked recessive genetic disease involving respiratory system damage [4].

In colorectal cancer, MSN silencing inhibits cell proliferation, adhesion, migration, and invasion, while overexpression accelerates these processes, indicating its role in CRC progression via the β-catenin-RUNX2 axis [2]. In triple-negative breast cancer, MSN significantly stimulates breast cancer cell proliferation and invasion in vitro and tumor growth in vivo, and targeting MSN or its downstream molecules shows potential as a therapeutic strategy [3].

In conclusion, Msn plays essential roles in maintaining normal immune function, and its mutations can lead to immunodeficiency-related diseases. In cancer, Msn promotes the progression of colorectal and triple-negative breast cancers. The study of Msn through genetic models helps in understanding the mechanisms of these diseases, providing potential targets for treatment.