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Research Article: A Zap70 gain-of-function mutation alters mouse thymic maturation

Date Published: 2026-10-06

Abstract:
The tyrosine kinase ZAP-70 is essential for T-cell activation and development, but the mechanisms regulating its activity remain unclear. Previous studies showed that the Src-family kinase LCK binds phosphorylated tyrosine 319 of ZAP-70 via its SH2 domain. Additionally, a gain-of-function ZAP-70 mutation involving the YEEI motif enhances LCK recruitment and TCR-mediated signaling. To investigate the physiological consequences of enhanced ZAP-70-LCK interaction in vivo , we generated a knock-in mouse model expressing the Zap70 YEEI gain-of-function mutation. Analysis of thymocyte development revealed that the Zap70 YEEI mutation altered T-cell maturation, resulting in increased differentiation of thymic regulatory T (Treg) cells and reduced thymic negative selection. In the peripheral T-cell compartment, mutant mice exhibited decreased surface expression of the TCR?? complex and an increased frequency of memory CD4 T cells. These findings indicate that enhancing the ZAP-70-LCK interaction modifies signaling thresholds during thymic selection and peripheral T-cell homeostasis. Collectively, our results demonstrate that a gain-of-function mutation in Zap70 significantly reshapes T-cell development and maturation, highlighting the importance of regulated ZAP-70-LCK interactions in establishing immune tolerance and maintaining T-cell compartment balance.

Introduction:
Host defense against malignancies and pathogens relies heavily on T cell-mediated immunity. The hallmark of this system is its antigen-specific recognition, which facilitates a potent yet self-controlled immune response across a vast array of challenges. Upon the engagement of the T cell receptor (TCR), a precisely orchestrated sequence of intracellular signaling pathways is initiated, driving the activation, expansion, and functional maturation of T cells. Furthermore, these signaling mechanisms are vital during…

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