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:IKKa, a major regulator of noncanonical and canonical NF-kB pathways, is essential for B-lymphocyte maturation and secondary lymph organ formation. No evidence of IKKa regulating early B cell development currently exists. Here we found reduced pre-pro-B and pro-B cells but increased myeloid-erythroid lineages in the bone marrow (BM) of knockin mice expressing reduced and kinase-dead IKKa (KA/KA). The KA/KA BM cells recaptured their defects in wild-type recipients and KA/KA fetal liver displayed reduced B cells but increased progenitors. IKKa inactivation impaired both NF-kB pathways and deregulated expression of many genes required for early B cell commitment and hematopoiesis, including downregulated Pax5, IRF4, and Ikaros expression, but increased C/EBPa, GATA1, and Stat3 levels. Reintroduced combined NF-kB components, Pax5, and IKKa promoted BM B cell differentiation and repressed myeloid-erythroid lineages. Our studies revealed a new function of IKKa in a coordinated development process of B-lineage and erythroid-myeloid lineages during hematopoiesis via multiple pathways. Microarray analysis was performed on RNA isolated from the BM of B220+ cells isolated from 4-week old WT and KA/KA mice using affymetrix mouse 430 2.0 array chip, containing 45,000 genes, at the Laboratory of Molecular Technology SAIC-Frederick. Data were normalized, and log2 transformations were generated using Partek software (St. Louis, MO, USA).
Project description:Drosophila mushroom body (MB) γ neurons undergo axon pruning during metamorphosis through a process of localized degeneration of specific axon branches. Developmental axon degeneration is initiated at the onset of metamorphosis by the pre-pupal rise in the steroid hormone ecdysone. This study identifies genes that alter their expression in MB neurons at the onset and early steps of axon pruning. Keywords: timecourse
Project description:Human pluripotent stem cells (hPSCs) provide a potential resource for the generation of functional blood cells in vitro. However, it remains largely unknown about the mechanism underlying hPSC-derived hematopoiesis. Here, we identified platelet endothelial aggregation receptor-1 (PEAR1) as a potential regulator of early hematopoietic development of hPSCs. We found that the expression of PEAR1 was gradually increased during endothelial and hematopoietic development. The hematopoietic potential was enriched in PEAR1+ population and PEAR1 could be used as a potential marker to enrich hemogenic endothelium. Moreover, knockout of PEAR1 impaired the hematopoietic potential of hPSCs. Collectively, our findings demonstrate that PEAR1 is required for early hematopoiesis and can be potentially used for establishing new strategies to produce more functional blood cells from hPSCs.
Project description:Multiple transcription factors regulate B cell commitment, which coordinates with myeloid–erythroid lineage differentiation. One such factor, NF-kB, has long been speculated to regulate early B cell development; however, this issue remains controversial. IKKa is required for splenic B cell maturation, but not for bone marrow (BM) B cell development. Here, we unexpectedly found defective BM B cell development and an increased myeloid–erythroid lineages in kinase-dead IKKa (KA/KA) knock-in mice. Markedly increased cytosolic p100, an NF-kB2 inhibitory form, and reduced nuclear NF-kB p65, RelB, p50, and p52, as well as IKKa, was observed in KA/KA splenic and BM B cells. Several B- and myeloid–erythroid-cell regulators, including Pax5, were deregulated in KA/KA BM B cells. Using fetal liver and BM congenic transplants, and IKKa deletion from early hematopoietic cells in mice, this defect was identified as B cell intrinsic and as an early event during hematopoiesis. Re-expression of IKKa, Pax5, or combined NF-kB molecules promoted B cell development, but repressed myeloid–erythroid cell differentiation in KA/KA BM B cells. Together, these results demonstrate that IKKa regulates B-lineage commitment via combined canonical and noncanonical NF-kB transcriptional activity to target Pax5 expression during hematopoiesis.
Project description:Here we tracked transcriptome changes over ten human hematopoietic stem and early progenitor populations, defining the transcriptional dynamics underlying the first steps of commitment. Most of the transcriptional programs observed extended beyond lineage boundaries. In particular, multi-lymphoid progenitors (MLPs) presented a hybrid transcriptional state with elements of lymphoid and myeloid programs, but also stem cell characteristics.