MS4A1 encodes CD20, a membrane-spanning protein primarily expressed on B-lymphocytes that serves multiple critical functions in immune regulation and calcium signaling. The protein functions as a store-operated calcium channel component, promoting calcium influx following B-cell receptor activation, which is essential for B-cell development, differentiation, and activation 1. CD20 interacts with multiple surface proteins including CD40, MHCII, CD53, CD81, and CD82, and its signaling propensity is linked to B-cell receptor function 1. Beyond B-cells, MS4A1 is also expressed in T-cell subsets, particularly CD8+CD20+ T cells that function in cancer immunosurveillance but are suppressed in tumor microenvironments 2. The gene produces multiple mRNA isoforms with distinct 5' untranslated regions that regulate CD20 protein expression through translational control mechanisms 3. In disease contexts, MS4A1 expression is associated with patient survival in colorectal cancer and serves as a therapeutic target, with anti-CD20 monoclonal antibodies like rituximab being widely used in B-cell malignancies 1 2. Additionally, MS4A1 has been implicated in lung adenocarcinoma progression through regulation of macrophage polarization via the HIPPO pathway 4.