Sialylated Glycans Regulate MUC13 and the Proto-Oncogenes Pim-1 and Myc to Control Hematopoietic Stem and Progenitor Cell Numbers

The enzyme β-1-4 galactosyltransferase 1 (β4GalT1) plays a critical role in thrombopoiesis by modulating sialo-glycan (sialyl N-acetyl-lactosamine or LacNAc) content and function of the β1 integrin on megakaryocytes (MKs) (Nat. Commun. 2020;11(1):356). Recent data, however, point to a more complex role for β4GalT1 in hematopoiesis, as the promoter region of its conserved gene, B4galt1, is rich in enhancer sequences for transcription factors associated with cell identity and pro-oncogenic regulatory programs. Here, we investigated the homeostasis of hematopoietic stem and progenitor cells (HSPCs) in B4galt1-/- mice. We demonstrate that lack of Sialylated LacNAc synthesis perturbs HSPCs beyond the homing deficiency associated with lack of homing sialo-glycan motifs. Flow cytometry analysis showed that B4galt1-/- mouse bone marrows have increased numbers of Long-Term HSCs (LT-HSCs, defined as LineageNeg/Sca-1Pos/c-KitPos/CD150Pos/CD48Neg). The increase in HSC numbers led us to investigate their phenotypic and functional features further. While quiescence markers in B4galt1-/- LT-HSCs were indistinguishable relative to controls, LT-HSCs expressed more of the platelet marker CD41 on their surface, supporting a highly expanded CD41+ subset of LT-HSCs. Platelet-bias of LT-HSCs has been associated with inflammation and aging. However, our data do not support an increased cytokine inflammatory profile in the bone marrow. Instead, single-cell RNA sequencing (scRNA seq) of sorted β4galt1-/- LineageNeg/Sca-1Pos/c-KitPos (LSK) cells showed a significantly increased expression of the proto-oncogene Pim-1, its target, Myc, and the heavily O-glycosylated transmembrane receptor mucin 13 (MUC13), compared to control cells. Analysis of LT-HSC glycan expression using lectin microarray showed the expected decrease in N-glycosylation associated with B4galt1 deficiency, but also an increase in O-glycans, consistent with overexpression of MUC13, expression of which was enriched compared to other surface mucins. The data show that B4galt1 deletion leads to overexpression of the proto-oncogenes Pim-1, Myc, and MUC13 in HSPCs. The data suggest that MUC13-associated O-glycans and glyco-synthetic genes are potential therapeutic targets for hematologic malignancies since mucins have anti-inflammatory functions and alterations in mucin expression are with inflammation and cancer. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Hematopoietic Stem and Progenitor Cells Locally Produce Neutrophils Necessary To Resolve S. Aureus-Infected Wounds

Blood ◽

10.1182/blood.v122.21.4710.4710 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4710-4710

Author(s):

Patrick C Falahee ◽

Jennifer L Granick ◽

Delsheen Dahmubed ◽

Scott I Simon

Keyword(s):

Progenitor Cells ◽

Conflicts Of Interest ◽

Critical Role ◽

Innate Immune ◽

Direct Stimulation ◽

Hematopoietic Stem ◽

On Demand ◽

Infected Wounds ◽

Stem And Progenitor Cells ◽

Deficient Mice

Staphylococcus aureus is a frequent cause of chronic nosocomial skin and soft tissue infections that can spread to muscle, bone and connective tissue. During the normal inflammatory response to infection, a heterogeneous population of circulating and bone marrow (BM)-derived cells are recruited to the site of injury that collectively contributes to host defense and tissue repair. Included among these are polymorphonuclear leukocytes (PMN), which serve a critical role as the first-line of defense in the innate immune response to S. aureus. Through detection and intervention of the number of PMN accessing the wound in a transgenic mouse model of S. aureus infected skin wounds, we discovered that a subset of hematopoietic stem and progenitor cells (HSPC) that are lineage negative, Sca-1+ and c-kit+ (LSK cells) traffic to the site of infection, where they undergo local granulopoiesis and account for up to 30% of total PMN found within the abscess. Blocking trafficking of LSK revealed that local expansion into PMN is critical for clearance of bacteria and efficient wound closure. To determine if toll like receptor (TLR) signaling contributed to local granulopoiesis, we compared the capacity of multi-potent LSK cells from WT, TLR2-deficient or MyD88-deficient mice transferred into wounds functioned in a similar manner to those trafficking into WT wounds in terms of PMN expansion and resolution of infection. LSK isolated and adoptively transferred from BM of WT mice into WT, TLR2-deficient or MyD88-deficient mice produced equivalent numbers of PMN and contributed to wound resolution. In contrast, LSK derived from TLR2- or MyD88-deficient mice that were transferred into WT wounds produced few PMN, indicating that TLR2 and MyD88 are both necessary for local granulopoiesis in response to S. aureus infection. The signaling pathway involved downstream production of PGE2 that acts in an autocrine manner to signal LSK cell expansion and myeloid proliferation. Local administration of PGE2 to infected wounds of TLR2- or MyD88-deficient mice restored PMN production and rescued resolution of infection in knockout mice. These findings shed light on a novel innate immune mechanism by which stem and progenitor cells traffic to S. aureus-infected wounds and produce PMN following direct stimulation in a manner dependent on TLR2/MyD88 signaling. Current studies are focused on the process of local granulopoiesis in terms of: The local granulopoietic niche and comparing it with myeloid proliferation in BM; The antibacterial capacity of PMN locally produced versus systemically recruited to the wound; Identification of molecular pathways parallel or downstream of PGE2 that are critical for on demand production of PMN within infection. An overall goal is to strategically manipulate the process of on demand production of PMN to more efficiently battle chronic and persistent infections as may occur in immune compromised patients. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

IP3 3-Kinase B Controls Hematopoietic Stem Cell Homeostasis and Prevents Lethal Hematopoietic Failure in Mice

Blood ◽

10.1182/blood.v124.21.250.250 ◽

2014 ◽

Vol 124 (21) ◽

pp. 250-250

Author(s):

Karsten Sauer

Keyword(s):

Stem Cell ◽

Hematopoietic Stem Cell ◽

Conflicts Of Interest ◽

Cell Activity ◽

Hematopoietic Stem ◽

Stem And Progenitor Cells ◽

Phosphoinositide 3 Kinase ◽

And Function

Tight regulation of hematopoietic stem cell (HSC) homeostasis ensures life-long hematopoiesis and prevents blood cancers. The mechanisms balancing HSC quiescence with expansion and differentiation into hematopoietic progenitors are incompletely understood. Here, we identify inositoltrisphosphate (IP3) 3-kinase B (Itpkb) as a novel essential regulator of HSC quiescence and function. Young Itpkb-/- mice accumulated phenotypic HSC which were less quiescent and proliferated more than wildtype controls. Itpkb-/- HSC downregulated quiescence and stemness associated mRNAs, but upregulated activation, oxidative metabolism, protein synthesis and lineage associated transcripts. Although they showed no significant homing defects and had normal to elevated viability, Itpkb-/- HSC had a severely reduced competitive long-term repopulating potential. Aging Itpkb-/- mice lost hematopoietic stem and progenitor cells and died with severe anemia. Wildtype HSC normally repopulated Itpkb-/- hosts, indicating a HSC-intrinsic Itpkb requirement. In vitro, Itpkb-/- HSC had reduced cobblestone-area forming cell activity and showed increased stem cell factor activation of the phosphoinositide 3-kinase (PI3K) effector Akt. This was reversed by exogenous provision of the Itpkb product IP4, a known PI3K/Akt antagonist. Itpkb-/- HSC also showed transcriptome changes consistent with hyperactive Akt/mTOR signaling. Thus, we propose that Itpkb ensures HSC quiescence and function in part by limiting cytokine-induced PI3K signaling in HSC. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Identification and Function of Hematopoietic Stem and Progenitor Cell Specific Micrornas.

Blood ◽

10.1182/blood.v116.21.2631.2631 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2631-2631

Author(s):

Bernhard Gentner ◽

Alice Giustacchini ◽

Francesco Boccalatte ◽

Giulia Schira ◽

Massimo Saini ◽

...

Keyword(s):

Cell Biology ◽

Conflicts Of Interest ◽

Human Cord Blood ◽

Hematopoietic Stem ◽

Long Run ◽

Stem And Progenitor Cells ◽

Phosphoinositide 3 Kinase ◽

And Function

Abstract Abstract 2631 Little is known about microRNA function in hematopoietic stem and progenitor cells (HSPC). Using a lentivector genetic reporter strategy to functionally detect miRNA activity in hematopoietic cells at single cell resolution, we identified several miRNAs which were specifically expressed in mouse and human HSC and early progenitors, defined according to cell surface phenotype and functional repopulation assays. One of these HSPC-specific miRNAs, miR-126, was further studied. We generated a stable miR-126 knockdown (kd) or forced its expression (“knock-in”, ki) in mouse HSPC using lentiviral vectors. Kd or ki cells were competitively transplanted with congenic, control vector-transduced cells, and hematopoietic chimerism was followed for >1 year in both primary and secondary recipients. miR-126 kd HSPC displayed enhanced myeloid and/or lymphoid contribution during the early phases of reconstitution, while they subsequently contributed similarly as the control cells. When this steady state bone marrow (BM) was transplanted into secondary recipients, we noted an even more pronounced over-contribution of miR-126 kd cells to hematopoiesis. In the long run, however, some secondary mice showed signs of exhaustion of miR-126 kd cells. These data suggest that miR-126 kd enhances hematopoiesis, likely at the stem/early progenitor level and in particular under stress conditions. On the other hand, forced expression of miR-126 (ki) resulted in an early competitive disadvantage in vivo, with progressively decreasing contribution to all hematopoietic lineages, paralleled by a nearly complete depletion of Kit+Sca+Lin- (KSL) miR-126 ki cells in the BM at 6 weeks after transplant. At 3 weeks post-transplant, when miR-126 ki KSL cells could still be detected, we found an increased proliferative index in these cells as judged by EdU incorporation in vivo, paralleled by a higher hematopoietic output respect to control cells at week 2–4 after transplant. These data suggest that miR-126 ki might favor HSC commitment at the cost of self-renewal. This phenotype was specific for miR-126 and not due to vector toxicity, as we demonstrate stable, long term overexpression of several control miRNAs in vivo. Moreover, miR-126 ki cells showed normal clonogenic activity in vitro. We then optimized a protocol to stably knock down miR-126 in human cord blood (huCB) HSPC, and validated this approach by demonstrating upregulation of previously described miR-126 targets including the beta subunit of phosphoinositide-3-kinase. Manipulation of miR-126 activity changed cell growth and differentiation of huCB, and we show altered activation of key signal transduction pathways upon miR-126 kd. Identification of additional miR-126 targets is ongoing using unbiased proteomic and transcriptomic approaches. In summary, these data suggest that a narrow range of miR-126 activity is required for robust and sustained HSC function, and that its manipulation may provide novel insights into stem cell biology. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

The role of the PZP domain of AF10 in acute leukemia driven by AF10 translocations

Nature Communications ◽

10.1038/s41467-021-24418-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Brianna J. Klein ◽

Anagha Deshpande ◽

Khan L. Cox ◽

Fan Xuan ◽

Mohamad Zandian ◽

...

Keyword(s):

Critical Role ◽

Cellular Transformation ◽

Acute Leukemias ◽

Hematopoietic Stem ◽

Nucleosome Core ◽

Stem And Progenitor Cells ◽

Transforming Activity

AbstractChromosomal translocations of the AF10 (or MLLT10) gene are frequently found in acute leukemias. Here, we show that the PZP domain of AF10 (AF10PZP), which is consistently impaired or deleted in leukemogenic AF10 translocations, plays a critical role in blocking malignant transformation. Incorporation of functional AF10PZP into the leukemogenic CALM-AF10 fusion prevents the transforming activity of the fusion in bone marrow-derived hematopoietic stem and progenitor cells in vitro and in vivo and abrogates CALM-AF10-mediated leukemogenesis in vivo. Crystallographic, biochemical and mutagenesis studies reveal that AF10PZP binds to the nucleosome core particle through multivalent contacts with the histone H3 tail and DNA and associates with chromatin in cells, colocalizing with active methylation marks and discriminating against the repressive H3K27me3 mark. AF10PZP promotes nuclear localization of CALM-AF10 and is required for association with chromatin. Our data indicate that the disruption of AF10PZP function in the CALM-AF10 fusion directly leads to transformation, whereas the inclusion of AF10PZP downregulates Hoxa genes and reverses cellular transformation. Our findings highlight the molecular mechanism by which AF10 targets chromatin and suggest a model for the AF10PZP-dependent CALM-AF10-mediated leukemogenesis.

Download Full-text

3008 – OXYGEN TENSION REGULATES CALCIUM SIGNALING AND FUNCTION IN HEMATOPOIETIC STEM AND PROGENITOR CELLS

Experimental Hematology ◽

10.1016/j.exphem.2020.09.030 ◽

2020 ◽

Vol 88 ◽

pp. S40

Author(s):

Paige Dausinas ◽

Jacob Slack ◽

Christopher Basile ◽

Anish Karlapudi ◽

Heather O'Leary

Keyword(s):

Calcium Signaling ◽

Progenitor Cells ◽

Oxygen Tension ◽

Hematopoietic Stem ◽

Stem And Progenitor Cells ◽

And Function

Download Full-text

Distinct roles of integrins α6 and α4 in homing of fetal liver hematopoietic stem and progenitor cells

Blood ◽

10.1182/blood-2006-10-051276 ◽

2007 ◽

Vol 110 (7) ◽

pp. 2399-2407 ◽

Cited By ~ 39

Author(s):

Hong Qian ◽

Elisabeth Georges-Labouesse ◽

Alexander Nyström ◽

Anna Domogatskaya ◽

Karl Tryggvason ◽

...

Keyword(s):

Progenitor Cells ◽

Fetal Liver ◽

Integrin Receptors ◽

Hematopoietic Stem ◽

Blocking Antibody ◽

Stem And Progenitor Cells ◽

Integrin Α4 ◽

And Function ◽

Blocking Antibodies

Homing of hematopoietic stem cells (HSCs) into the bone marrow (BM) is a prerequisite for establishment of hematopoiesis during development and following transplantation. However, the molecular interactions that control homing of HSCs, in particular, of fetal HSCs, are not well understood. Herein, we studied the role of the α6 and α4 integrin receptors for homing and engraftment of fetal liver (FL) HSCs and hematopoietic progenitor cells (HPCs) to adult BM by using integrin α6 gene–deleted mice and function-blocking antibodies. Both integrins were ubiquitously expressed in FL Lin−Sca-1+Kit+ (LSK) cells. Deletion of integrin α6 receptor or inhibition by a function-blocking antibody inhibited FL LSK cell adhesion to its extracellular ligands, laminins-411 and -511 in vitro, and significantly reduced homing of HPCs to BM. In contrast, the anti-integrin α6 antibody did not inhibit BM homing of HSCs. In agreement with this, integrin α6 gene–deleted FL HSCs did not display any homing or engraftment defect compared with wild-type littermates. In contrast, inhibition of integrin α4 receptor by a function-blocking antibody virtually abrogated homing of both FL HSCs and HPCs to BM, indicating distinct functions for integrin α6 and α4 receptors during homing of fetal HSCs and HPCs.

Download Full-text

Critical role for Gimap5 in the survival of mouse hematopoietic stem and progenitor cells

The Journal of Cell Biology ◽

10.1083/jcb1933oia7 ◽

2011 ◽

Vol 193 (3) ◽

pp. i7-i7

Author(s):

Yuhong Chen ◽

Mei Yu ◽

Xuezhi Dai ◽

Mark Zogg ◽

Renren Wen ◽

...

Keyword(s):

Progenitor Cells ◽

Critical Role ◽

Hematopoietic Stem ◽

Stem And Progenitor Cells

Download Full-text

Astrocyte-neuron crosstalk through Hedgehog signaling mediates cortical circuit assembly

10.1101/2020.07.15.204263 ◽

2020 ◽

Author(s):

Yajun Xie ◽

Aaron T. Kuan ◽

Wengang Wang ◽

Zachary T. Herbert ◽

Olivia Mosto ◽

...

Keyword(s):

Cortical Neurons ◽

Molecular Mechanisms ◽

Synapse Formation ◽

Critical Role ◽

Shh Signaling ◽

Shh Pathway ◽

Cortical Astrocytes ◽

Functional Features ◽

And Function ◽

Circuit Assembly

SUMMARYNeuron-glia relationships play a critical role in the regulation of synapse formation and neuronal specification. The cellular and molecular mechanisms by which neurons and astrocytes communicate and coordinate are not well understood. Here we demonstrate that the canonical Sonic hedgehog (Shh) pathway is active in cortical astrocytes, where it acts to coordinate layer-specific synaptic connectivity and functional circuit development. We show that Ptch1 is a Shh receptor that is expressed by cortical astrocytes during development and that Shh signaling is necessary and sufficient to promote the expression of layer-specific astrocyte genes involved in regulating synapse formation and function. Loss of Shh in layer V neurons reduces astrocyte complexity and coverage by astrocytic processes in tripartite synapses, moreover, cell-autonomous activation of Shh signaling in astrocytes promotes cortical excitatory synapse formation. Together, these results suggest that Shh secreted from deep layer cortical neurons acts to specialize the molecular and functional features of astrocytes during development to shape circuit assembly and function.

Download Full-text

Re-Exposure of Cord Blood (CB) to Non-Inherited Maternal HLA Antigens (NIMA) Improves Transplant Outcome in Patients (pts) with Hematologic Malignancies and May Reduce Relapse.

Blood ◽

10.1182/blood.v114.22.661.661 ◽

2009 ◽

Vol 114 (22) ◽

pp. 661-661

Author(s):

Jon J van Rood ◽

Cladd E Stevens ◽

Jacqueline Smits ◽

Carmelita Carrier ◽

Carol Carpenter ◽

...

Keyword(s):

Conflicts Of Interest ◽

Chronic Gvhd ◽

Hla Antigens ◽

Human Leukocyte ◽

Hematologic Malignancies ◽

Hematopoietic Stem ◽

Leukocyte Antigens ◽

Grade Ii ◽

The Impact ◽

Related Mortality

Abstract Abstract 661 CB hematopoietic stem cell transplantation (CBT) can be successful even if donor and recipient are not fully matched for human leukocyte antigens (HLA). This may result, at least in part, from tolerance-inducing events during pregnancy, but this concept has not been tested to date. Hence we analyzed the impact of fetal exposure to NIMA of the HLA-A, -B antigens or -DRB1 alleles on the outcome of 1121 pts with hematologic malignancies. All pts received single CB units provided by the NYBC, for treatment of ALL (N=451), AML (N=376), CML (N=116), MDS (N=79), other (N=99); 22% were transplanted in advanced stage. Median age was 9.7 years (range: 0.1-67); 29% of recipients were >16 years. Most pts (96%) received myeloablative cytoreduction. Sixty-two pts received fully matched grafts while 1059 received units mismatched (MM) for one or two HLA antigens. Of these, 79 (7%) had a MM antigen which was identical to a donor NIMA (Example: Pt: A1, A3; CBU: A1, A2; mother-CBU: A1, A3; A3 is NIMA). NIMA match was found in 25 recipients with one HLA MM and 54 of those with two MM. The NIMA match was identified after the transplant and was not used in unit selection. In multivariate analyses, NIMA matched transplants (NMTs), showed faster neutrophil recovery (RR=1.3, p=0.043), even for grafts with cell dose <3×107 (RR=1.6, p=0.053). There was no difference in the incidence of acute (grade II-IV) or chronic GvHD. 3-year relapse risk (cumulative incidence 22%) was reduced compared to 1 or 2 HLA MM no NIMA matched transplants, especially in pts with myelogenous malignancies given units with 1 HLA MM (RR=0.2, p=0.074). Further, 3-year transplant-related mortality was reduced (RR=0.7, p=0.034), particularly in pts ≥5 years old (RR=0.5, p=0.006), as was the 3-year overall mortality (RR= 0.7, p=0.029 and RR=0.6, p=0.015, respectively). As a result, in the NMTs, treatment failure (relapse or death) was significantly lower, particularly in pts ≥5 years (RR=0.7, p=0.019) and DFS was significantly improved (figure) and was similar to that of the 0 HLA MM group. These findings are the first indication that donor exposure to NIMA can improve post-transplant survival in unrelated CBT and might reduce relapse. We propose to include the NIMA of CB units in search algorithms. Thus, for pts lacking fully HLA matched grafts, HLA MM but NIMA matched CB units could be selected preferentially, since no adverse effects were seen. This strategy of selecting HLA MM grafts with optimal outcome effectively “expands” the current CB Inventory several-fold.Patient GroupNRR(95% Cl)p value0 MM360.5(0.3–0.8)0.0051 MM / NIMA Match180.4(0.2–0.9)0.0262 MM / NIMA Match400.8(0.5–1.2)0.3091 MM / No NIMA Match229reference group2 MM / No NIMA Match4871.1(0.9–1.3)0.365 Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Characterization of Hematopoietic Stem Cell Frequency and Function In Unexplained Anemia of the Elderly

Blood ◽

10.1182/blood.v116.21.2047.2047 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2047-2047

Author(s):

Wendy Pang ◽

Elizabeth Price ◽

Irving L. Weissman ◽

Stanley L. Schrier

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

In Vitro Culture ◽

Progenitor Cells ◽

The Elderly ◽

Elderly Subjects ◽

Hematopoietic Stem ◽

Stem And Progenitor Cells ◽

And Function

Abstract Abstract 2047 Anemia is both a highly prevalent and clinically important condition that causes significant morbidity and mortality in the elderly population. While anemia in the elderly can be attributed to a number of causes, approximately 30% of elderly subjects with anemia have no overt etiology and fall under the category of unexplained anemia of the elderly (UA). There is increasing evidence to suggest that changes in the frequency and/or function of hematopoietic stem and progenitor cells may contribute to the onset and pathophysiology of age-associated hematological conditions, such as UA. Hematopoietic stem cells (HSC) reside at the top of the hematopoietic hierarchy and can differentiate, via increasingly committed downstream progenitors, into all the mature cells of the hematopoietic system. Human myelo-erythroid development proceeds through a set of oligopotent progenitors: HSC give rise to multipotent progenitors (MPP), which give rise to common myeloid progenitors (CMP), which in turn give rise to granulocyte-macrophage progenitors (GMP) and megakaryocyte-erythrocyte progenitors (MEP). We use flow cytometry and in vitro culture of sorted human HSC (Lin-CD34+CD38-CD90+CD45RA-), MPP (Lin-CD34+CD38-CD90-CD45RA-), CMP (Lin-CD34+CD38+CD123+CD45RA-), GMP (Lin-CD34+CD38+CD123+CD45RA+), and MEP (Lin-CD34+CD38+CD123-CD45RA-) from hematologically normal young (23 samples; age 20–35) and elderly (11 samples; age 65+) and UA (5 samples; age 65+) bone marrow samples in order to characterize the changes in the distribution and function of hematopoietic stem and progenitor populations during the aging process and, in particular, in the development of UA. We found that UA patients contain higher frequencies of HSC compared to both elderly normal (1.5-fold; p<0.03) and young normal samples (2.8-fold; p<10-5). We also found increased frequencies of MPP from UA patients compared to MPP from elderly normal (2.6-fold; p<0.002) and young normal samples (5.8-fold; p<0.04). While we observed similar frequencies of CMP among the three groups, we found a notable trend suggesting decreased frequencies of GMP and corresponding increased frequencies of MEP in UA patients. Functionally, HSC from the three groups exhibit statistically insignificant differences in the efficiency of colony formation under the myeloid differentiation-promoting methylcellulose-based in vitro culture conditions; however, on average, HSC from elderly bone marrow samples, regardless of the presence or absence of anemia, tend to form fewer colonies in methylcellulose. Interestingly, HSC from UA patients produce more granulocyte-monocyte (CFU-GM) colonies and fewer erythroid (CFU-E and BFU-E) colonies, compared to HSC from normal samples (p<0.001). Similarly, CMP from UA patients, compared to normal CMP, yield skewed distributions of myeloid-erythroid colonies when plated in methylcellulose, significantly favoring production of CFU-GM colonies over CFU-E and BFU-E colonies (p<0.003). Additionally, MEP from UA patients form both CFU-E and BFU-E colonies in methylcellulose albeit at a significantly lower efficiency than MEP from normal bone marrow samples (p<0.01). This is the first study to examine the changes in hematopoietic stem and progenitor populations in UA patients. The changes in the distribution of hematopoietic stem and progenitor cells in UA patients indicate that the HSC and MPP populations, and possibly also the MEP population, expand in the context of anemia, potentially in response to homeostatic feedback mechanisms. Nevertheless, these expanded populations are functionally impaired in their ability to differentiate towards the erythroid lineage. Our data suggest that there are intrinsic defects in the HSC population of UA patients that lead to poor erythroid differentiation, which can be readily observed even in the earliest committed myelo-erythroid progenitors. We have generated gene expression profiling data from these purified hematopoietic stem and progenitor populations from UA patients to try to identify biological pathways and markers relevant to disease pathogenesis and potential therapeutic targets. Disclosures: Weissman: Amgen, Systemix, Stem cells Inc, Cellerant: Consultancy, Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Schrier:Celgene: Research Funding.

Download Full-text