Project description:Ligation of the B cell antigen receptor (BCR) initiates humoral immunity. However, mere BCR signaling without appropriate co-stimulation commits B cells to death rather than to differentiation into immune effector cells. How BCR activation depletes potentially autoreactive B cells while simultaneously primes for receiving rescue and differentiation signals from cognate T lymphocytes remains unknown. Here, using a mass spectrometry-based proteomic approach to identify cytosolic/nuclear shuttling elements, we uncover transcription factor EB (TFEB) as a central BCR-controlled rheostat that drives activation-induced apoptosis, and concurrently, promotes the reception of co-stimulatory rescue signals by supporting B cell migration and antigen presentation. CD40 co-stimulation prevents TFEB-driven cell death, while enhancing and prolonging TFEB’s nuclear residency, which hallmarks antigenic experience also of memory B cells. In mice, TFEB shapes the transcriptional landscape of germinal center B cells. Within the germinal center, TFEB facilitates the dark zone entry of light-zone-residing centrocytes through regulation of chemokine receptors and, by balancing the expression of Bcl-2/BH3-only family members, integrates antigen-induced apoptosis with T cell-provided CD40 survival signals. Thus, TFEB reprograms antigen-primed germinal center B cells for cell fate decisions.
Project description:Comparison of gene expression differences between Dnmt3L heterozygous and wildtype pachytene spermatocytes, and similarly between Dnmt3L heterozygous and wildtype round spermatids which were isolated from the Dnmt3L knockout mouse line. This array was conducted to address the hypothesis that Dnmt3L heterozygosity results in deregulated gene expression within spermatocytes and spermatids. Results show that Dnmt3L heterozygosity causes numerous genes to be differentially regulated on a genome-wide level, showing that DNMT3L has an important role in regulating gene expression within these male germ cells.
Project description:Serum response factor (SRF) is a transcription factor essential for cell proliferation, differentiation, and migration, and is required for primitive streak and mesoderm formation in the embryo. The canonical roles of SRF are mediated by a diverse set of context-dependent cofactors. Here we show that SRF physically interacts with CTCF and cohesin subunits at TAD boundaries and loop anchors. SRF reinforces the insulation of TADs and promotes the formation of long-range chromatin loops. In ES cells, SRF associates with Oct4, Sox2, and Nanog and contributes to the formation of 3D pluripotency hubs. Our findings reveal new roles of SRF in higher-order chromatin organization.
Project description:Klhl6 belongs to the KLHL gene family, which is composed of an N-terminal BTB-POZ domain and 4 to 6 Kelch motifs in tandem. Several of these proteins function as adaptors of the Cullin3 E3 ubiquitin ligase complex. Here we report that Klhl6 deficiency induces, as previously described, a two-fold reduction in mature B cells. However, we find that this deficit is centered on the inability of transitional T1 B cells to survive and to progress toward the T2 B cell stage, whereas cells that have passed this step generate normal germinal centers upon a T-dependent immune challenge. Klhl6-deficient T1 B cells showed a two-fold over-expression of genes linked with cell proliferation, including most targets of the APC/C complex, a set of genes whose expression is precisely down-modulated upon culture of splenic transitional B cells in presence of BAFF. These results thus suggest a delay in the differentiation process of Klhl6-deficient B cells between the immature and transitional stage. We further show, in the BL2 Burkitt’s lymphoma cell line, that KLHL6 interacts with Cullin3, but also that it binds to HBXIP/Lamtor5, a protein involved in cell cycle regulation and cytokinesis. Finally, we report that KLHL6, which is recurrently mutated in B cell lymphomas, is an off-target of the normal somatic hypermutation process taking place in germinal center B cells in both mice and humans, thus leaving open, whether, in spite of the lack of impact of Klhl6 deficiency on germinal center B cell expansion, mutants could contribute to the oncogenic process.
Project description:The first wave of hematopoiesis is the primitive hematopoiesis, which produces embryonic erythroid and myeloid cells. Primitive erythrocytes are thought to be generated from bipotent hemangioblasts, but the molecular basis remains unclear. Transcriptional repressors Gfi1aa and Gfi1b have been shown to cooperatively promote primitive erythrocytes differentiation from hemangioblasts in zebrafish. However, the mechanism of these repressors during the primitive wave is largely unknown. Herein, by functional analysis of zebrafish gfi1aasmu10, gfi1bsmu11, gfi1absmu12 single, double, and triple mutants, we found that Gfi1aa not only plays a predominant role in primitive erythropoiesis but also synergizes with Gfi1ab. To screen Gfi1aa downstream targets, we performed RNA-seq and ChIP-seq analysis and found two endothelial transcription factors, etv2 and sox7, to be repressed by Gfi1aa. Genetic analysis demonstrated Gfi1aa to promote hemangioblast differentiation into primitive erythrocytes by inhibiting both etv2 and sox7 in a Lsd1-dependent manner. Moreover, the H3K4me1 level of etv2 and sox7 were increased in gfi1aa mutant. Taken together, these results suggest that Gfi1aa/Lsd1-dependent etv2/sox7 downregulation is critical for hemangioblast differentiation during primitive hematopoiesis by inhibition of endothelialization. The different and redundant roles for Gfi1(s), as well as their genetic and epigenetic regulation during primitive hematopoiesis, help us to better know the molecular basis of the primitive hematopoiesis and sheds light on the understanding the Gfi1(s) related pathogenesis.
Project description:Comparison of gene expression differences between Dnmt3L heterozygous and wildtype pachytene spermatocytes, and similarly between Dnmt3L heterozygous and wildtype round spermatids which were isolated from the Dnmt3L knockout mouse line. This array was conducted to address the hypothesis that Dnmt3L heterozygosity results in deregulated gene expression within spermatocytes and spermatids. Results show that Dnmt3L heterozygosity causes numerous genes to be differentially regulated on a genome-wide level, showing that DNMT3L has an important role in regulating gene expression within these male germ cells. Three preparations each of Dnmt3L purified wildtype spermatocytes, wildtype spermatids, heterozygous spermatids, and two preparations of heterozygous spermatocytes were isolated for a total of 11 samples. Each preparation was made up of cells isolated from 10 mice.