Project description:Cells from the myeloid and lymphoid lineages fulfill distinct functions with specific shapes and intra-cellular architectures. The role of cytokines in the regulation of HSC differentiation has been intensively studied but our understanding of the potential contribution of inner cell architecture is relatively poor. Here we studied the early commitment of human HSC and identified specific microtubule network rearrangements and nucleus shape changes that accompany cells differentiation toward the myeloid lineage. This work established the role of microtubules in the mechanical regulation of nucleus shape, chromatin architecture and HSC differentiation and open new perspectives in our appreciation of the implication of intra-cellular forces in the early specification of the myeloid lineage.
Project description:Breast carcinoma amplified sequence 2 (BCAS2), a core component of the hPrP19 complex, plays crucial roles in various physiological and pathological processes. However, whether BCAS2 has functions other than being a key RNA-splicing regulator within the nucleus remains unknown. Here, we show that BCAS2 is essential for primitive hematopoiesis in zebrafish and mouse embryos. The activation of Wnt/β-catenin signal, which is required for hematopoietic progenitor differentiation, is significantly decreased upon depletion of bcas2 in zebrafish embryos and mouse embryonic fibroblasts (MEFs). Interestingly, BCAS2 deficiency has no obvious impact on the splicing efficiency of β-catenin pre-mRNA, while significantly attenuating β-catenin nuclear accumulation. Moreover, we find that BCAS2 directly binds to β-catenin via its coiled-coil domains, thereby sequestering β-catenin within the nucleus. Thus, our results uncover a previously unknown function of BCAS2 in promoting Wnt signaling by enhancing β-catenin nuclear retention during primitive hematopoiesis.
Project description:Proper control of inflammatory responses is essential for embryonic development, but the underlying mechanism is poorly understood. Here, we show that under physiological conditions, inactivation of ISG15, an inflammation amplifier, is associated with the interaction of Beclin 1 (Becn1), via its ECD domain, with STAT3 in the major fetal hematopoietic organ of mice. Conditional loss of Becn1 caused sequential dysfunction and exhaustion of fetal liver hematopoietic stem cells, leading to lethal inflammatory cell-biased hematopoiesis in the fetus. Molecularly, the absence of Becn1 resulted in the release of STAT3 from Becn1 tethering and subsequent phosphorylation and translocation to the nucleus, which in turn directly activated the transcription of ISG15 in fetal liver hematopoietic cells, coupled with increased ISGylation and production of inflammatory cytokines, whereas inactivating STAT3 reduced ISG15 transcription and inflammation but improved hematopoiesis potential, and further silencing ISG15 mitigated the above collapse in the Becn1 null hematopoietic lineage. The Becn1-STAT3-ISG15 axis remains functional in Atg5/7-disrupted fetal hematopoietic organs. These results suggest that Becn1, in an autophagy-independent manner, secures hematopoiesis and survival of the fetus by directly inhibiting STAT3-ISG15 activation to prevent cytokine storms. Our findings highlight a previously undocumented role of Becn1 in governing ISG15 to safeguard the fetus.
Project description:Human cytomegalovirus extensively alters nuclear organization and the cellular transcriptome, yet our understanding of these events remains relatively limited. Here, chromatin conformation capture reveals that cytomegalovirus dramatically alters chromosome organization at both large-scale and local compartment levels. Nascent transcriptomics further reveals the extent to which transcriptional changes correlate with compartment changes, while also uncovering infection-induced read-in and read-through events that result in the expression of normally repressed neuronal genes in infected fibroblasts. Moreover, we find that viral genomes preferentially localize to the most abundant and euchromatic compartments of the host, further dysregulating transcription of subsets of host genes. Finally, we show that microtubule-derived forces on the nucleus regulate viral interactions with host chromatin as well as local compartment interactions, which in turn influences infection-induced transcriptional reprogramming. Combined, our findings reveal the extent to which HCMV alters chromatin organization and transcriptional activity, along with the contribution of microtubules to these processes.
Project description:Human cytomegalovirus extensively alters nuclear organization and the cellular transcriptome, yet our understanding of these events remains relatively limited. Here, chromatin conformation capture reveals that cytomegalovirus dramatically alters chromosome organization at both large-scale and local compartment levels. Nascent transcriptomics further reveals the extent to which transcriptional changes correlate with compartment changes, while also uncovering infection-induced read-in and read-through events that result in the expression of normally repressed neuronal genes in infected fibroblasts. Moreover, we find that viral genomes preferentially localize to the most abundant and euchromatic compartments of the host, further dysregulating transcription of subsets of host genes. Finally, we show that microtubule-derived forces on the nucleus regulate viral interactions with host chromatin as well as local compartment interactions, which in turn influences infection-induced transcriptional reprogramming. Combined, our findings reveal the extent to which HCMV alters chromatin organization and transcriptional activity, along with the contribution of microtubules to these processes.