Tcf-1 (encoded by Tcf7) not only plays critical roles in promoting T cell development and differentiation but also has been identified as a tumor suppressor involved in preventing T cell malignancy. However, the comprehensive mechanisms of Tcf-1 involved in T cell transformation remain poorly understood. In this study, Tcf7^fl/fl mice were crossed with Vav-cre, Lck-cre, or Cd4-cre mice to delete Tcf-1 conditionally at the beginning of the HSC, DN2–DN3, or DP stage, respectively. The defective T cell development phenotypes became gradually less severe as the deletion stage became more advanced in distinct mouse models. Interestingly, consistent with Tcf7^−/− mice, Tcf7^fl/flVav-cre mice developed aggressive T cell lymphoma within 45 weeks, but no tumors were generated in Tcf7^fl/flLck-cre or Tcf7^fl/flCd4-cre mice. Single-cell RNA-seq (ScRNA-seq) indicated that ablation of Tcf-1 at distinct phases can subdivide DN1 cells into three clusters (C1, C2, and C3) and DN2–DN3 cells into three clusters (C4, C5, and C6). Moreover, Tcf-1 deficiency redirects bifurcation among divergent cell fates, and clusters C1 and C4 exhibit high potential for leukemic transformation. Mechanistically, we found that Tcf-1 directly binds and mediates chromatin accessibility for both typical T cell regulators and proto-oncogenes, including Myb, Mycn, Runx1, and Lyl1 in the DN1 phase and Lef1, Id2, Dtx1, Fyn, Bcl11b, and Zfp36l2 in the DN2–DN3 phase. The aberrant expression of these genes due to Tcf-1 deficiency in very early T cells contributes to subsequent tumorigenesis. Thus, we demonstrated that Tcf-1 plays stage-specific roles in regulating early thymocyte development and transformation, providing new insights and evidence for clinical trials on T-ALL leukemia.

Tcf-1（由Tcf7编码）不仅在促进 T 细胞发育和分化中起关键作用，而且已被确定为参与预防 T 细胞恶性肿瘤的肿瘤抑制因子。然而，Tcf-1 参与 T 细胞转化的综合机制仍然知之甚少。在本研究中，将 Tcf7 ^fl/fl小鼠与Vav -cre、Lck -cre 或Cd4 -cre 小鼠杂交，分别在 HSC、DN2-DN3 或 DP 阶段开始时有条件地删除 Tcf-1。随着缺失阶段在不同的小鼠模型中变得更加先进，有缺陷的 T 细胞发育表型逐渐变得不那么严重。有趣的是，与Tcf7一致^-/-小鼠，Tcf7 ^fl/fl Vav -cre 小鼠在 45 周内发展为侵袭性 T 细胞淋巴瘤，但在Tcf7 ^fl/fl Lck -cre 或Tcf7 ^fl/fl Cd4 -cre 小鼠中未产生肿瘤。单细胞 RNA-seq (ScRNA-seq) 表明，在不同阶段消融 Tcf-1 可以将 DN1 细胞细分为三个簇（C1、C2 和 C3），并将 DN2-DN3 细胞细分为三个簇（C4、C5 和C6)。此外，Tcf-1 缺乏重定向了不同细胞命运之间的分叉，并且簇 C1 和 C4 表现出很高的白血病转化潜力。从机制上讲，我们发现 Tcf-1 直接结合并介导典型 T 细胞调节因子和原癌基因（包括Myb ）的染色质可及性, Mycn , Runx1和Lyl1在 DN1 阶段和Lef1, Id2, Dtx1, Fyn, Bcl11b和Zfp36l2在 DN2-DN3 阶段。由于非常早期的 T 细胞中 Tcf-1 缺乏，这些基因的异常表达有助于随后的肿瘤发生。因此，我们证明了 Tcf-1 在调节早期胸腺细胞发育和转化中发挥阶段特异性作用，为 T-ALL 白血病的临床试验提供了新的见解和证据。