Zinc finger protein Zfp335 controls early T cell development and survival through β-selection-dependent and -independent mechanisms

T cell development in the thymus undergoes the process of differentiation, selective proliferation and survival from CD4 ^- CD8 ^- double negative (DN) stage to CD4 ⁺ CD8 ⁺ double positive (DP) stage prior to the formation of CD4 ⁺ helper and CD8 ⁺ cytolytic T cells ready for circulation. Each developmental stage is tightly regulated by sequentially-operating molecular networks, of which only limited numbers of transcription regulators have been deciphered. Here we identified Zfp335 transcription factor as a new player in the regulatory network controlling thymocyte development. We demonstrate that Zfp335 intrinsically controls DN to DP transition, as T cell-specific deficiency in Zfp335 leads to a substantial accumulation of DN3 along with reduction of DP, CD4 ⁺ and CD8 ⁺ thymocytes. This developmental blockade at DN stage results from the impaired intracellular TCRβ expression as well as increased susceptibility to apoptosis in thymocytes. Transcriptomic and ChIP-seq analyses revealed a direct regulation of transcription factors Bcl6 and Rorc by Zfp335. Importantly, enhanced expression of TCRβ and Bcl6/RorγT restores the developmental defect during DN3 to DN4 transition and improves thymocytes survival, respectively. These findings identify a critical role of Zfp335 in controlling T cell development by maintaining intracellular TCRβ expression-mediated β- selection and independently activating cell survival signaling.