Project description:We compared gene expression differences in Lyl-1 knockout vs wildtype LMPPs KO allele described in Pub Med ID: 21387538 LMPPS were purified as Lineage-negative, Sca-1+ c-Kit+ (LSK) and Flt3-high from both Lyl1-null and WT mice on C57Bl/6 background
Project description:The first lymphoid-restricted progeny of hematopoietic stem cells (HSCs) are lymphoid-primed multipotent progenitors (LMPPs), which have little erythromyeloid potential but retain lymphoid, granulocyte, and macrophage differentiation capacity. Despite recent advances in the identification of LMPPs, the transcription factors essential for their generation remain to be identified. Here, we demonstrated that the E2A transcription factors were required for proper development of LMPPs. Within HSCs and LMPPs, E2A proteins primed expression of a subset of lymphoid-associated genes and prevented expression of genes that are not normally prevalent in these cells, including HSC-associated and nonlymphoid genes. E2A proteins also restricted proliferation of HSCs, MPPs, and LMPPs and antagonized differentiation of LMPPs toward the myeloid fate. Our results reveal that E2A proteins play a critical role in supporting lymphoid specification from HSCs and that the reduced generation of LMPPs underlies the severe lymphocyte deficiencies observed in E2A-deficient mice.
Project description:We report the gene expression profile of single cell BM LMPPs that are either responsive to Notch signals, or unresponsive to Notch signals due to absence of expression of RBPJ, a key mediator of the Notch signaling pathway.
Project description:We compared gene expression differences in Atxn1L knockout vs wildtype HSCs KO allele described in Pub Med ID: 22014525 HSCs were purified as Lineage-negative, Sca-1+ c-Kit+ (LSK), CD150+ and Side population from both Atxn1L-null and WT mice on C57Bl/6 background
Project description:The transcription factor PU.1 is a central regulator of hematopoiesis, required for the normal differentiation of the myeloid and lymphoid lineages. Due to its essential role in early development and the importance of PU.1 in regulating several defining markers of lymphoid progenitors, its precise function in early lymphopoiesis has remained unclear. Using conditional mutagenesis and alternative lineage identification strategies, we demonstrate the developmental stage restricted function for PU.1 in early lymphopoiesis. PU.1 was required for efficient generation of “lymphoid primed multipotent progenitors (LMPPs)” from hematopoietic stem cells and was essential for the subsequent formation of “common lymphoid progenitors (CLPs)”. In contrast, further differentiation into the B cell lineage was independent of PU.1. The function of PU.1 was dosage sensitive as loss of one allele decreased all stages of early lymphopoiesis. PU.1 expression mirrored its functional role during lineage differentiation. PU.1 peaked at LMPPs and was maintained in CLPs, before being down regulated in committed pro-B cells. Examination of the transcriptional changes in PU.1 conditionally deficient LSK cells revealed that PU.1 activates lymphoid and dendritic cell associated genes in LMPPs, while repressing genes normally expressed in neutrophils. These data identify PU.1 as a critical regulator of lymphoid priming and the transition between LMPPs and CLPs.
Project description:Capturing where and how multipotency is lost is crucial to understand how blood formation is controlled. Blood lineage specification is currently thought to occur downstream of multipotent haematopoietic stem cells (HSC). Here we show that, in human, the first lineage restriction events occur within the CD19-CD34+CD38-CD45RA-CD49f+CD90+ (49f+) HSC compartment to generate myelo-lymphoid committed cells with no erythroid differentiation capacity. At single-cell resolution, we observe a continuous but polarised organisation of the 49f+ compartment, where transcriptional programmes and lineage potential progressively change along a gradient of opposing cell surface expression of CLEC9A and CD34. CLEC9AhiCD34lo cells contain long-term repopulating multipotent HSCs with slow quiescence exit kinetics, whereas CLEC9AloCD34hi cells are restricted to myelo-lymphoid differentiation and display infrequent but durable repopulation capacity. We thus propose that human HSCs gradually transition to a discrete lymphoid-primed state, distinct from lymphoid-primed multipotent progenitors, representing the earliest entry point into lymphoid commitment.
Project description:Tcf1 is necessary for optimal T lineage development. Tcf1 deficient progenitors fail to initiate the T lineage program in vitro and development is severely defective in vivo. We used microarrays to assess the overal global gene expression differences from Tcf1 wildtype and deficient lymphoid biased progenitors cultures on Notch-ligand expressing stroma to determine if Tcf1 deficient progenitors are able to intiate the T lineage specification program. Abstract of manuscript: The thymus imposes the T cell fate on incoming multipotent progenitors, but the molecular mechanisms are poorly understood. We show that transcription factor Tcf1 initiates T-lineage-specific gene expression. Tcf1 is downstream of Notch1 signaling and expressed in early T-cell progenitors. Progenitors deficient for Tcf1 are unable to initiate normal T-lineage specification. Conversely, ectopic expression of Tcf1 in hematopoietic progenitors is sufficient to induce expression of T-lineage specific genes in vitro. Thus, our study identifies Tcf1 as critically involved in the establishment T cell identity. Tcf1 wildtype and deficient bone marrow lymphoid primed progenitors (LMPPs, Lineage marker- Sca+kit+Flt3high) were harvested in triplicate and seeded onto OP9-DL4 expressing stroma for 4 days upon which highly pure lineage negative and Thy1+CD25+ T cells were cell sorted for expression analysis. The lineage negative populations represent three seperate mice from each genotype and the Thy1+CD25+T lineage population represents two replicates from the Tcf1 wildtype group. No Thy1+CD25+ T lineage cells develop from Tcf1 deficient progentiors.
Project description:LMPPs comprise of heterogeneous populations which are progenitors of lymphocytes and myeloid cells. We aim to identify the difference of distribution of the diverse populations from CP-CML versus BC-CML patients.
Project description:T cells have the potential to maintain immunological memory and self-tolerance by recognizing antigens from pathogens or tumors. In pathological situations, failure to generate de novo T cells causes immunodeficiency resulting in acute infections and complications. Hematopoietic stem cells (HSC) transplantation constitutes a valuable option to restore proper immune function. However, delayed T cell reconstitution is observed compared to other lineages. To overcome this difficulty, we developed a new approach to identify populations with efficient lymphoid reconstitution properties. To this end, we use a DNA barcoding strategy based on the insertion into a cell chromosome of a lentivirus (LV) carrying a non-coding DNA fragment named barcode (BC). These will segregate through cell divisions and be present in cells' progeny. The remarkable characteristic of the method is that different cell types can be tracked simultaneously in the same mouse. Thus, we in vivo barcoded LMPP and CLP progenitors to test their ability to reconstitute the lymphoid lineage. Barcoded progenitors were co-grafted in immuno-compromised mice and their fate analyzed by evaluating the BC composition in transplanted mice. The results highlight the predominant role of LMPP progenitors for lymphoid generation and reveal valuable novel insights to be reconsidered in clinical transplantation assays.