Martinez-A, C. | bioRxiv Science

bioRxiv2021

Chromatin reader Dido3 regulates the genetic network of B cell differentiation

The development of hematopoietic cell lineages is a highly complex process that is governed by a delicate interplay of various transcription factors. The expression of these factors is influenced, in part, by epigenetic signatures that define each stage of cell differentiation. In particular, the formation of B lymphocytes depends on the sequential silencing of stemness genes and the balanced expression of interdependent transcription factors, along with DNA rearrangement. We have investigated the impact that the deficiency of DIDO3, a protein involved in chromatin status readout, has on B cell differentiation within the hematopoietic compartment of mice. Our findings revealed significant impairments in the successive stages of B cell development. The absence of DIDO3 resulted in remarkable alterations in the expression of essential transcription factors and differentiation markers, which are crucial for orchestrating the differentiation process. In addition, the somatic recombination process, which is responsible for generation of antigen receptor diversity, was also adversely affected. These observations highlight the vital role of epigenetic regulation, in particular the involvement of DIDO3, in ensuring proper B cell differentiation. This study show new mechanisms underlying disruptive alterations which deepen our understanding of hematopoiesis and may potentially lead to insights that aid in the development of therapeutic interventions for disorders involving aberrant B cell development.

molecular biology↗

bioRxiv2021

Mitochondrial oxidative stress drives IL-12/IL-18-induced IFN-gamma production by CD4+ T cells and is controlled by Fas

Mitochondrial activation and mROS production are crucial for CD4+ T cell responses and have a role in naive cell signaling after TCR activation. However, little is known about their role in recall responses driven by cytokine signaling. Here, we found that mROS are required for IL-12 plus IL-18-driven production of IFN-{gamma}, an essential cytokine in inflammatory and autoimmune disease development. In particular, memory-like cells obtained after activation-induced differentiation showed faster and augmented mROS accumulation and increased IFN-{gamma} production in response to IL-12 plus IL-18 compared to naive T cells. In contrast, mROS induction was similar in naive and memory-like cells after TCR-dependent signaling. Taken together these results suggested that memory-like CD4+ T cells treated by IL-12 plus IL-18 attained conditions for an extraordinary mROS-producing potential. mROS inhibition significantly downregulated the production of IFN-{gamma} and the expression of CD44 activation marker, suggesting a direct mROS effect on the activation of memory-like T cells. Mechanistically, mROS was required for optimal activation of key signaling pathways that drive IFN-{gamma} production after IL-12 plus IL-18 T cell stimulation, such as PKC-{theta}, AKT and STAT4 phosphorylation, and NF-{kappa}B activation. Notably, we identified increased mROS as key promoters of hyperactivation and IFN-{gamma} overproduction in Fas-deficient lpr memory-like CD4+ T cells compared to WT cells, following IL-12 plus IL-18 stimulation. mROS inhibition significantly reduced the population of disease-associated CD44hiCD62Llo lpr CD4+ T cells and their IFN-{gamma} production. These findings uncover a previously unidentified role for Fas in regulating mitochondrial ROS production by memory-like T cells. This apoptosis-independent Fas activity might contribute to the accumulation of CD44hiCD62Llo CD4+ T cells that produce increased IFN-{gamma} levels in lpr mice. Overall, our findings pinpoint mROS as central regulators of TCR-independent signaling, and support mROS pharmacological targeting to control aberrant immune responses in autoimmune-like disease.

immunology↗