Coiled-coil domain containing 134 (CCDC134), a characterized secreted protein, may serve as an immune cytokine and illustrates its potent antitumor effects by augmenting CD8+ T-cell-mediated immunity. Additionally, CCDC134 may also act as a novel regulator of human alteration/deficiency in activation 2a, and be involved in the p300-CBP-associated factor complex and affect its acetyltransferase activity. To clarify the biological and pathological function of CCDC134, the present study generated a viable and fertile Ccdc134fl/fl mouse strain that allowed temporal and spatial control of gene ablation. Ccdc134−/− embryos generated by crossing of Ccdc134fl/fl mice with human β-actin-Cre or zona pellucida 3-Cre transgenic mice were embryonic lethal from embryonic day (E)12.5 to birth. Ccdc134 loss was associated with severe hemorrhages in the brain ventricular space and neural tube, pale and abnormal livers, cardiac hypertrophy and placental distress. Furthermore, it was demonstrated that a fraction of E13.5 fetal livers and brains exhibited reduced cell proliferation and vascular endothelial cell defects. CCDC134 also exhibited a dynamic and specific expression pattern during embryo development. The present results suggest that Ccdc134 may have specific biological functions in regulating mouse embryonic development.

Modulation of surface T cell antigen receptor (TCR) expression is crucial for proper T cell development and maintenance of mature T cell function at steady state and upon stimulation. We previously determined that CCDC134 (coiled-coil domain containing 134), a cytokine-like molecule that served as a potential member of the γc cytokine family, contributes to antitumor responses by augmenting CD8+ T cell-mediated immunity. Here we show that T cell-specific deletion of Ccdc134 decreased peripheral mature CD4+ and CD8+ T cells, which resulted in impaired T cell homeostasis. Moreover, Ccdc134-deficient T cells exhibited an attenuated response to TCR stimulation in vitro, showing lower activation and proliferative capacity. This was further reflected in vivo, rendering mice refractory to T cell-mediated inflammatory and antitumor responses. More importantly, CCDC134 is associated with TCR signaling components, including CD3ϵ, and attenuated TCR signaling in Ccdc134-deficient T cells via altered CD3ϵ ubiquitination and degradation. Taken together, these findings suggest a role for CCDC134 as a positive regulator of TCR-proximal signaling and provide insight into the cell-intrinsic functional consequences of Ccdc134 deficiency in the attenuation of T cell-mediated inflammatory and antitumor responses.