Project description:NFATc1 plays a critical role in double-negative thymocyte survival and differentiation. However, the signals that regulate Nfatc1 expression are unknown. Here we show a developmental stage-specific differential expression pattern of Nfatc1 driven by the distal (P1) or proximal (P2) promoters in thymocytes. Whereas, preTCR-negative thymocytes exhibited only P2 promoter-derived Nfatc1b expression, preTCR-positive thymocytes expressed both Nfatc1b and P1 promoter-derived Nfatc1a transcripts. Inducing NFATc1a activity from P1 promoter in preTCR-negative thymocytes, in addition to the NFATc1a from P2 promoter impaired thymocyte development resulting in severe T cell lymphopenia. Additionally, we show that NFATc1 activity suppressed the B-lineage potential of immature thymocytes, and consolidated their differentiation to T cells. Further, in the pTCR-positive DN3 cells, a threshold level of NFATc1 activity was vital in facilitating T cell differentiation and to prevent T-acute lymphoblastic leukemia (T-ALL) development. Altogether, our results show NFATc1 activity is crucial in determining the T cell fate of thymocytes.
Project description:In thymus hematopoietic precursor cells differentiate into αβ T cells, γδ T cells, mucosa-associated invariant T cells (MAIT), and natural killer T (NKT) cells. We show that both ablation of NFATc1 or its induction during the DN stages of thymocyte development leads to an almost normal thymocyte development but a marked increase in γδ T cells. The γδ cells deficient for NFATc1 acquire an NKT γδ cell phenotype that exhibits the expression of CD4 co-receptor, the NK1.1 marker, the augmented usage of the Vγ1.1 and Vδ6.3 segments, and an increased in IL4 and IFN-γ production.
Project description:In thymus hematopoietic precursor cells differentiate into αβ T cells, γδ T cells, mucosa-associated invariant T cells (MAIT), and natural killer T (NKT) cells. We show that both ablation of NFATc1 or its induction during the DN stages of thymocyte development leads to an almost normal thymocyte development but a marked increase in γδ T cells. The γδ cells deficient for NFATc1 acquire an NKT γδ cell phenotype that exhibits the expression of CD4 co-receptor, the NK1.1 marker, the augmented usage of the Vγ1.1 and Vδ6.3 segments, and an increased in IL4 and IFN-γ production.
Project description:In thymus hematopoietic precursor cells differentiate into αβ T cells, γδ T cells, mucosa-associated invariant T cells (MAIT), and natural killer T (NKT) cells. We show that both ablation of NFATc1 or its induction during the DN stages of thymocyte development leads to an almost normal thymocyte development but a marked increase in γδ T cells. The γδ cells deficient for NFATc1 acquire an NKT γδ cell phenotype that exhibits the expression of CD4 co-receptor, the NK1.1 marker, the augmented usage of the Vγ1.1 and Vδ6.3 segments, and an increased in IL4 and IFN-γ production.
Project description:The endocardium interacts with the myocardium to promote proliferation and morphogenesis during the later stages of heart development. However, the role of the endocardium in early cardiac ontogeny remains under-explored. Given the shared origin, subsequent juxtaposition, and essential cell-cell interactions of endocardial and myocardial cells throughout heart development, we hypothesized that paracrine signaling from the endocardium to the myocardium is critical for initiating early differentiation of myocardial cells. To test this, we generated an in vitro, endocardial-specific ablation model using the diphtheria toxin receptor under the regulatory elements of the NFATc1 genomic locus (NFATc1-DTR) Early treatment of NFATc1-DTR embryoid bodies with diphtheria toxin efficiently ablated endocardial cells, which significantly attenuated the percent of beating EBs in culture and expression of early and late myocardial differentiation markers. The addition of Bmp2 during endocardial ablation partially rescued myocyte differentiation, maturation and function. Therefore, we conclude that early stages of myocardial differentiation rely on endocardial paracrine signaling mediated in part by Bmp2. Our findings provide novel insight into early endocardial-myocardial interactions that can be explored to promote early myocardial development and growth.
Project description:Lmo2 is an oncogenic transcription factor that is a frequent target of chromosomal abnormalities in this T-cell acute lymphoblastic leukemia (T-ALL). In transgenic mouse models, overexpression of Lmo2 causes thymocyte self-renewal leading to T-cell leukemia with long latency. However, the requirement of Lmo2 for maintenance of overt leukemia is poorly understood. We found that Lyl1, a critical cofactor for Lmo2-induced leukemia, is frequently lost in cell lines derived from Lmo2-transgenic mice, raising the possibility that Lmo2 function is dispensable at this stage. To study this, we developed a Tetracycline-repressible knock-in mouse model (Vav-TRE-Lmo2), which expresses Lmo2 throughout the haematopoietic system. This led to specific effects on T-cell development and the development of T-cell leukemia with long latency, preceded by the presence of self-renewing T-cells in the thymus. Repression of Lmo2 overcame the Lmo2-induced thymocyte developmental block at the preleukemic stage and led to elimination of Lmo2-induced thymocyte self-renewal in vivo. In contrast, Lmo2 function was dispensable for the majority of overt Lmo2-induced T-cell leukemias as well as leukemia-derived cell lines, implying an evolution of oncogene addiction in the majority of T-cell leukemias. Lmo2-dependence in T-ALL was associated with an immature gene expression profile, but could not be predicted by immunophenotype or assessment of Notch pathway activation. Thus, Lmo2 can give rise to both Lmo2-depenent and –independent T-cell leukemias. The Vav-TRE-Lmo2 model should be useful to determine the molecular features associated with Lmo2-dependence, as well as the critical components of the Lmo2-induced self-renewal pathways in T-ALL.