Epidermal growth factor-like domain 8 inhibits the survival and proliferation of mouse thymocytes.

Thymic epithelial cells (TECs) play a critical role in T-cell development through their intercellular interactions and by producing various soluble proteins, such as growth factors, cytokines and chemokines. In this study, we report a new role for epidermal growth factor-like domain 8 (EGFL8) in the regulation of the survival and proliferation of mouse thymocytes. Mouse recombinant EGFL8 (rEGFL8) protein was produced using an E. coli system and its biological role in mouse thymocytes was determined. The injection of rEGFL8 in mice in vivo resulted in a decrease in the weight of the thymus, as well as in the number of total thymocytes; rEGFL8 also inhibited thymocyte proliferation and induced thymocyte apoptosis. Furthermore, rEGFL8 suppressed the expression of the Notch downstream targets, Hes1 and Hey1, in mouse thymocytes and TECs, indicating that EGFL8 negatively regulates the Notch signaling pathway in these cells. The identification of the role of EGFL8 in thymocytes may aid in the determination of the fate of thymocytes during T-cell development.