Clonal Evolution In Fanconi Anemia; The Role of HOXA9

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 126-126
Author(s):  
Grover C Bagby ◽  
Jane Yates ◽  
Praveen Anur ◽  
Keaney Rathbun ◽  
Christina Harrington ◽  
...  
Keyword(s):  
Fanconi Anemia ◽  
Bone Marrow Failure ◽  
Clonal Evolution ◽  
Ectopic Expression ◽  
Gene Signature ◽  
Inhibitory Response ◽  
Myelogenous Leukemia ◽  
Analytical Approaches ◽  
Marrow Cells

Abstract Abstract 126 Bone marrow failure in patients with Fanconi anemia (FA) is often complicated by the clonal neoplasms myelodysplasia (MDS) and acute myelogenous leukemia (AML). FA stem cells (HSC) exhibit self-replicative defects and HSC and committed progenitor cells (HPC) from Fancc-deficient (Fancc −/−) mice and FA-C-deficient patients are hypersensitive to suppressive cytokines, particularly TNFα, a cytokine also known to be overproduced by Fancc−/− macrophages. In fact, in Fancc−/− mice overproduction of TNFα plays an important role in both marrow failure and evolution of TNF-resistant neoplastic clones. To test the notion that evolution of clones in patients with FA might follow a like adaptive pathway to TNF-resistance, we performed gene expression microarray analysis (Affymetrix GeneChip HG-U133A [22,283 probe sets] arrays) using RNA obtained from low-density marrow cells from; (a) normal volunteers (NV, n=11) (b) FA patients with clonal cytogenetic defects detected in at least 50% of metaphases (FA-CL, n=10) and (c) FA patients with no detectable cytogenetic defects (FA-APL, n=22). Data were normalized using the MAS 5.0 global scaling method with the target intensity of 325. The adapted nature of evolved clones was supported by unsupervised hierarchical clustering (GeneSifter) and principal component analyses (Partek) which revealed a high degree of relatedness between the NV and FA-CL samples while FA-APL samples were more distant from both NV and FA-CL in transcriptomal space. To identify genes whose differential expression might play a role in clonal evolution, two analytical approaches were taken. First, using the shrunken centroids method we identified a 30 gene signature that distinguished FA-CL and FA-APL samples. Secondly, we applied two filters to the data. The first revealed 2317 genes that were either over-expressed or under-expressed (>1.5 fold, p<0.05, adjusted for multiple comparisons using the Benjamini-Hochberg method) in a pairwise comparison of FA-APL to NV samples. The second filter utilized a pattern reading tool (GeneSifter) to identify those genes on the first list of 2317 whose expression did not differ in the comparison between NV and FA-CL samples. The majority (959 of 1063) of these genes were those whose expression was suppressed in FA-APL samples and either not-suppressed or overexpressed in the FA-CL samples. Three genes of interest were in the 30 gene signature identified using the shrunken centroids method and in those identified using the pattern reading tool. Specifically, HOXA9, a gene with known leukemogenic potential, and two genes known to enhance the expression of HOXA9 (MYB and KDM5B) were suppressed in FA-APL samples and over-expressed in the FA-CL samples. After confirming the RNA results using quantitative real time RT-PCR and subsequently determining that the differentially expressed genes in the FA-CL samples included most of the genes known to be regulated by HOXA9 expression in CD34+ marrow cells (Dorsam,S.T. et al, Blood 2004) (p<0.05, Fisher's Exact P.T.) we demonstrated the following: (a) retroviral expression of HOXA9 in normal human CD34+ marrow cells enhanced TNFα resistance in CFU-GM and BFU-E, (b) 3-day in vitro exposure of kit+/lin−/sca-1+ (KLS) cells from Fancc−/− mice to TNFα and multilineage growth factors (MGF; IL-11, Flt3L, SCF, IL-6) suppressed expression of HoxA9 and suppressed survival of KLS cells but enhanced expression of HoxA9 and enhanced survival of wild-type KLS cells, (c) ectopic expression of HOXA9 in Fancc−/− KLS cells enhanced KLS survival and blunted the inhibitory response to TNFα in 3-day suspension cultures with MGF. Taken together, these results indicate that clonal evolution in FA stem cell pools represents the ascendance of a fundamentally adapted clone and that over-expression of HOXA9 in the clonal progeny may represent at least one early step in the pathway of clonal adaptation. Disclosures: Pasquini: Novartis: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria.

scholarly journals Long-term bone marrow culture in persons with Fanconi anemia and bone marrow failure

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 336-339 ◽  
Author(s):  
A Butturini ◽  
RP Gale
Keyword(s):  
Bone Marrow ◽  
Fanconi Anemia ◽  
Autosomal Recessive ◽  
Autosomal Recessive Disease ◽  
Bone Marrow Failure ◽  
Myelogenous Leukemia ◽  
Acute Myelogenous ◽  
Nonadherent Cells

Abstract Fanconi anemia is an autosomal recessive disease characterized by a high risk of developing bone marrow (BM) failure and acute myelogenous leukemia. We studied growth of hematopoietic progenitor cells in long- term BM culture (LTBMC) in 8 persons with Fanconi anemia and BM failure. Although LTBMC were initiated with very few BM cells, an adherent layer formed in cultures from 7 persons. In these cultures, the number of nonadherent cells increased for 10 to 15 days. Cell growth continued until cultures were terminated at day 35 to 40. During the first 2 weeks of culture, most nonadherent cells were differentiated myeloid cells. By days 35 to 40, the adherent layer contained cells able to initiate secondary LTBMCs. These data indicate that hematopoietic precursors cells able to proliferate and differentiate in vitro are present in the BM of persons with Fanconi anemia and BM failure. They suggest that mechanisms other than absent precursor cells are responsible for BM failure in Fanconi anemia.

scholarly journals Long-term bone marrow culture in persons with Fanconi anemia and bone marrow failure

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 336-339
Author(s):  
A Butturini ◽  
RP Gale
Keyword(s):  
Bone Marrow ◽  
Fanconi Anemia ◽  
Autosomal Recessive ◽  
Autosomal Recessive Disease ◽  
Bone Marrow Failure ◽  
Myelogenous Leukemia ◽  
Acute Myelogenous ◽  
Nonadherent Cells

Fanconi anemia is an autosomal recessive disease characterized by a high risk of developing bone marrow (BM) failure and acute myelogenous leukemia. We studied growth of hematopoietic progenitor cells in long- term BM culture (LTBMC) in 8 persons with Fanconi anemia and BM failure. Although LTBMC were initiated with very few BM cells, an adherent layer formed in cultures from 7 persons. In these cultures, the number of nonadherent cells increased for 10 to 15 days. Cell growth continued until cultures were terminated at day 35 to 40. During the first 2 weeks of culture, most nonadherent cells were differentiated myeloid cells. By days 35 to 40, the adherent layer contained cells able to initiate secondary LTBMCs. These data indicate that hematopoietic precursors cells able to proliferate and differentiate in vitro are present in the BM of persons with Fanconi anemia and BM failure. They suggest that mechanisms other than absent precursor cells are responsible for BM failure in Fanconi anemia.

scholarly journals Ectopic HOXB4 overcomes the inhibitory effect of tumor necrosis factor-α on Fanconi anemia hematopoietic stem and progenitor cells

Blood ◽  
2009 ◽  
Vol 113 (21) ◽  
pp. 5111-5120 ◽  
Author(s):  
Michael D. Milsom ◽  
Bernhard Schiedlmeier ◽  
Jeff Bailey ◽  
Mi-Ok Kim ◽  
Dandan Li ◽  
...  
Keyword(s):  
Tumor Necrosis Factor ◽  
Fanconi Anemia ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Ectopic Expression ◽  
Hematopoietic Stem ◽  
Tnf Α ◽  
Factor Α ◽  
Necrosis Factor

AbstractEctopic delivery of HOXB4 elicits the expansion of engrafting hematopoietic stem cells (HSCs). We hypothesized that inhibition of tumor necrosis factor-α (TNF-α) signaling may be central to the self-renewal signature of HOXB4. Because HSCs derived from Fanconi anemia (FA) knockout mice are hypersensitive to TNF-α, we studied Fancc−/− HSCs to determine the physiologic effects of HOXB4 on TNF-α sensitivity and the relationship of these effects to the engraftment defect of FA HSCs. Overexpression of HOXB4 reversed the in vitro hypersensitivity to TNF-α of Fancc−/− HSCs and progenitors (P) and partially rescued the engraftment defect of these cells. Coexpression of HOXB4 and the correcting FA-C protein resulted in full correction compared with wild-type (WT) HSCs. Ectopic expression of HOXB4 resulted in a reduction in both apoptosis and reactive oxygen species in Fancc−/− but not WT HSC/P. HOXB4 overexpression was also associated with a significant reduction in surface expression of TNF-α receptors on Fancc−/− HSC/P. Finally, enhanced engraftment was seen even when HOXB4 was expressed in a time-limited fashion during in vivo reconstitution. Thus, the HOXB4 engraftment signature may be related to its effects on TNF-α signaling, and this pathway may be a molecular target for timed pharmacologic manipulation of HSC during reconstitution.

scholarly journals In vitro restoration of polyclonal hematopoiesis in a chronic myelogenous leukemia after in vitro treatment with 4- hydroperoxycyclophosphamide

Blood ◽  
1985 ◽  
Vol 65 (3) ◽  
pp. 753-757 ◽  
Author(s):  
G Degliantoni ◽  
L Mangoni ◽  
V Rizzoli
Keyword(s):  
Bone Marrow ◽  
Chronic Myelogenous Leukemia ◽  
Early Phase ◽  
Bone Marrow Cells ◽  
Type A ◽  
G6pd Activity ◽  
Myelogenous Leukemia ◽  
Stem Cell Population ◽  
Marrow Cells

Bone marrow cells of a 45-year-old female with Philadelphia chromosome (Ph1)-positive, early-phase chronic myelogenous leukemia (CML), who was heterozygous for the glucose-6-phosphate dehydrogenase (G6PD) locus, were pretreated in vitro with 4-hydroperoxycyclophosphamide (4-HC) and tested for G6PD activity in several colony formation assays and for karyotypic abnormalities. All cells within the mixed (CFU-GEMM), the erythroid burst (BFU-E), and the granulocyte-macrophage (CFU-GM) colonies expressed type A and type B G6PD activity and a normal karyotype, whereas untreated cells expressed type A G6PD and the Ph1 chromosome. This reversal of G6PD activity type and the disappearance of the Ph1 chromosome in colonies grown from 4-HC-treated cells indicate that this cytotoxic agent spares a residual normal stem cell population in bone marrow cells of early-phase CML patients. This finding, in turn, suggests a therapeutic approach in CML based on in vitro chemotherapy of autologous bone marrow grafts.

Phenotypic correction of Fanconi anemia group C knockout mice

Blood ◽  
2000 ◽  
Vol 95 (2) ◽  
pp. 700-704 ◽  
Author(s):  
Kimberly A. Gush ◽  
Kai-Ling Fu ◽  
Markus Grompe ◽  
Christopher E. Walsh
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Mitomycin C ◽  
Fanconi Anemia ◽  
Bone Marrow Cells ◽  
Bone Marrow Failure ◽  
Genetic Disorder ◽  
Hematopoietic Stem ◽  
Marrow Cells

Fanconi anemia (FA) is a genetic disorder characterized by bone marrow failure, congenital anomalies, and a predisposition to malignancy. FA cells demonstrate hypersensitivity to DNA cross-linking agents, such as mitomycin C (MMC). Mice with a targeted disruption of the FANCC gene (fancc −/− nullizygous mice) exhibit many of the characteristic features of FA and provide a valuable tool for testing novel therapeutic strategies. We have exploited the inherent hypersensitivity offancc −/− hematopoietic cells to assay for phenotypic correction following transfer of the FANCC complementary DNA (cDNA) into bone marrow cells. Murine fancc −/− bone marrow cells were transduced with the use of retrovirus carrying the humanfancc cDNA and injected into lethally irradiated recipients. Mitomycin C (MMC) dosing, known to induce pancytopenia, was used to challenge the transplanted animals. Phenotypic correction was determined by assessment of peripheral blood counts. Mice that received cells transduced with virus carrying the wild-type gene maintained normal blood counts following MMC administration. All nullizygous control animals receiving MMC exhibited pancytopenia shortly before death. Clonogenic assay and polymerase chain reaction analysis confirmed gene transfer of progenitor cells. These results indicate that selective pressure promotes in vivo enrichment offancc-transduced hematopoietic stem/progenitor cells. In addition, MMC resistance coupled with detection of the transgene in secondary recipients suggests transduction and phenotypic correction of long-term repopulating stem cells.

Fas-Mediated Modulation of Bcr/Abl in Chronic Myelogenous Leukemia Results in Differential Effects on Apoptosis

Blood ◽  
1998 ◽  
Vol 92 (3) ◽  
pp. 981-989 ◽  
Author(s):  
Carmine Selleri ◽  
Jaroslaw P. Maciejewski ◽  
Fabrizio Pane ◽  
Luigia Luciano ◽  
Anna Maria Raiola ◽  
...  
Keyword(s):  
Chronic Myelogenous Leukemia ◽  
Chronic Phase ◽  
Poor Response ◽  
Inhibitory Response ◽  
Myelogenous Leukemia ◽  
Poor Responders ◽  
Cd34 Cells ◽  
In Cells

Abstract Fas-R is expressed constitutively in CD34+ cells of patients with chronic myelogenous leukemia (CML); Fas-R triggering results in decreased proliferation rate due to apoptosis of clonogenic cells. We have already shown that α-interferon (IFN-α) enhances Fas-R expression on CML progenitor cells, thus increasing their sensitivity to Fas-R agonists. Although it appears that IFN-α can prime CML cells for the effects of Fas, the response to IFN-α in vivo is not a constant feature in CML patients. We studied the mechanisms of Fas-mediated apoptosis in 11 patients suffering from CML in chronic phase and tried to see whether there was a correlation between in vitro inducibility of apoptosis in CD34+ CML cells after Fas-R triggering and the clinical response to IFN-α. After priming with IFN-α, Fas triggering resulted in in vitro suppression of hematopoietic cell growth in seven of eight patients who had optimal hematologic response to IFN-α; in the same conditions, no inhibitory response to Fas-R agonist was observed in cells from three of three patients who proved to be poor responders to IFN-α. In responders to IFN-α, Fas-R agonist induced dose-dependent apoptosis of CD34+ cells; this effect was associated with a decrease in the bcr/abl protein level. In cells derived from patients with a poor response to IFN-α, the rate of apoptosis in culture remained unchanged in the presence of Fas-R agonist and nobcr/abl downmodulation was observed. Finally, we measuredbcr/abl mRNA by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and found that decreased bcr/ablprotein after Fas triggering was not associated with decreased amounts of specific mRNA, a finding which is consistent with a posttranscriptional regulation of the bcr/abl protein expression. It appears that Fas-mediated downmodulation of p210bcr/abl restores susceptibility to apoptosis of CML cells; in addition, in vitro studies on CML cells may predict response to IFN-α treatment. © 1998 by The American Society of Hematology.

Xeroderma Pigmentosum as a Model for Treatment of Bone Marrow Failure in Fanconi Anemia and Aplastic Anemia.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4235-4235
Author(s):  
W. Clark Lambert ◽  
Santiago A. Centurion
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Fanconi Anemia ◽  
Xeroderma Pigmentosum ◽  
Bone Marrow Failure ◽  
S Phase ◽  
White Female ◽  
Cross Linking

Abstract We have previously shown that the primary cell cycle defect in the inherited, cancer-prone, bone marrow failure associated disease, Fanconi anemia (FA), is not in the G2 phase of the cell cycle, as had been thought for many years, but rather in the S phase. FA cells challenged with the DNA cross-linking agent, psoralen coupled with long wavelength, ultraviolet (UVA) radiation (PUVA), fail to slow their progression through the S phase of the subsequent cell cycle, as do normal cells. FA cells are extremely sensitive to the cytotoxic and clastogenic effects of DNA cross-linkers, such as PUVA, so much so that the diagnosis of FA is based on an assay, the “DEB test”, in which cells are examined for clastogenic and cytotoxic effects of diepoxybutane (DEB), a DNA cross-linking agent. More recently, we have shown that artificially slowing the cell cycle of FA cells exposed to PUVA by subsequent treatment with agents which slow their progression through S phase leads to markedly increased viability and reduced chromosome breakage in vitro. We now show that similar results can be obtained in vivo in patients with another DNA repair deficiency disease, xeroderma pigmentosum (XP), a recessively inherited disorder associated with defective repair of sunlight induced adducts in the DNA of sun-exposed tissues followed by development of numerous mutations causing large numbers of cancers in these same tissues. We treated two patients with XP, a light complected black male and a white female, both 14 years of age, in sun-exposed areas with 5-fluorouracil, an inhibitor of DNA synthesis, daily for three months. In contrast to normal patients, who only show clinical results if an inflammatory response is invoked, marked improvement in the clinical appearance of the skin was seen with no inflammation observed. This effect was confirmed histologically by examining epidermis adjacent to excised lesions in sun-exposed areas and further verified by computerized image analysis. Treatment with agents that slow progression through S phase, such as hydroxyurea, may similarly improve clinical outcomes in patients with FA or others who are developing bone marrow failure.

Modeling Bone Marrow Failure and MDS in Shwachman Diamond Syndrome Using Induced Pluripotent Stem Cells

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1496-1496 ◽  
Author(s):  
Melisa Ruiz-Gutierrez ◽  
Ozge Vargel Bolukbasi ◽  
Linda Vo ◽  
Ryohichi Sugimura ◽  
Marilyn Sanchez Bonilla ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Progenitor Cells ◽  
Bone Marrow Failure ◽  
Clonal Evolution ◽  
Chromosome 7 ◽  
Stem Cell Markers ◽  
Hematopoietic Stem ◽  
Monosomy 7

Abstract Myelodysplastic syndrome (MDS) caused by monosomy 7 or del(7q) is a frequent clonal abnormality that arises in the context of inherited bone marrow failure syndromes, such as Shwachman Diamond Syndrome (SDS). Monosomy 7/del(7q) also develops in a subset of patients with acquired aplastic anemia or de novo MDS in the general population. Monosomy 7/del(7q) is associated with high grade MDS and a high risk of malignant transformation, most frequently to acute myelogenous leukemia (AML). Bone marrow failure and clonal evolution to MDS and AML remain major causes of morbidity and mortality for individuals with SDS. Currently, the only curative therapy for these hematological complications is a hematopoietic stem cell transplant. Prognosis is extremely poor once SDS patients develop leukemia. The basis for this propensity to develop monosomy 7 clones remains unclear. The longterm aim of this study is to understand the molecular mechanisms underlying leukemia predisposition and develop more effective treatments. Whether monosomy 7/del(7q) functions as a driver of MDS, or is merely an associated marker of clonal progression in bone marrow failure remains a critical question. The lack of synteny between murine versus human chromosome 7 has posed a major barrier to the development of mouse models of monosomy 7/del(7q). To study the biological and molecular consequences of monosomy 7/del(7q) in SDS, induced pluripotent stem cells (iPSCs) were generated from bone marrow mononuclear cells of two patients with SDS. Each patient harbored homozygous c.258+2 T>C mutations in the canonical splice donor site of intron 2 in the SBDS gene. The SDS-iPSCs retained the pathogenic homozygous IVS2+2 T>C SBDS mutations, expressed stem cell markers, formed teratomas, and expressed reduced levels of SBDS protein similar to levels noted in the primary patient samples. Proliferation of 4 distinct SDS-iPSC clones derived from two different patients was reduced relative to wild type controls without an increase in cell death. SDS-iPSC formed smaller embryoid bodies with reduced production of CD34+ hematopoietic stem/progenitor cells. Hematopoietic differentiation from CD34+ to CD45+ cells was also impaired. Preliminary data suggest that SDS-iPSCs retain the capacity to give rise to hematopoietic stem/progenitor cells and early myeloid progenitor cells in vitro. These populations were also observed in primary SDS patient-derived bone marrow samples. Because the number of CD34+ cells derived from SDS-iPSCs are limiting, a previously reported 5 transcrition factor re-specification system was used to expand multilineage hematopietic progenitors for further characterization. SDS iPSCs were able to differentiate into an expandable CD34+ population in vitro. Further studies to characterize the hematopoietic impairment in SDS iPSC and primary marrow samples are ongoing. To model del(7q) in SDS iPSCs, a deletion of the MDS-associated long arm of chromosome 7 was genomically engineered using a previously published modified Cre-Lox approach. The deletion of 7q at locus (11.2) was confirmed by karyotyping and by qPCR across chromosome 7. The SDS (del7q) iPSCs retained the SBDS pathogenic mutations, expressed stem cell markers, and formed teratomas. Proliferation of the SDS del(7q) iPSC was markedly impaired compared to isogenic SDS iPSCs. No increase in cell death was observed in the SDS del7q iPSCs. Studies are in progress to determine the effects of del7q on hematopoiesis. Investigation is ongoing to determine the molecular consequences of deleting 7q. These isogenic SDS+/- del(7q) iPS models provide a platform to study the role of 7q loss in clonal evolution from bone marrow failure and to screen for novel therapeutic compounds or pathways to treat bone marrow failure and MDS. Disclosures No relevant conflicts of interest to declare.

Clonal chromosomal aberrations in bone marrow cells of Fanconi anemia patients: gains of the chromosomal segment 3q26q29 as an adverse risk factor

Blood ◽  
2003 ◽  
Vol 101 (10) ◽  
pp. 3872-3874 ◽  
Author(s):  
Holger Tönnies ◽  
Stefanie Huber ◽  
Jörn-Sven Kühl ◽  
Antje Gerlach ◽  
Wolfram Ebell ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Risk Factor ◽  
Fanconi Anemia ◽  
Bone Marrow Cells ◽  
Bone Marrow Failure ◽  
Molecular Cytogenetics ◽  
Complementation Group ◽  
Significant Survival ◽  
High Incidence ◽  
Marrow Cells

Abstract Fanconi anemia (FA) is a condition that induces susceptibility to bone marrow failure, myelodysplastic syndrome (MDS), and leukemia. We report on a high incidence of expanding clonal aberrations with partial trisomies and tetrasomies of chromosome 3q in bone marrow cells of 18 of 53 FA patients analyzed, detected by conventional and molecular cytogenetics. To determine the clinical relevance of these findings, we compared the cytogenetic data, the morphologic features of the bone marrow, and the clinical course of these patients with those of 35 FA patients without clonal aberrations of 3q. The 2 groups did not differ significantly with respect to age, sex, or complementation group. There was a significant survival advantage of patients without abnormalities of chromosome 3q. Even more pronounced was the risk assessment of patients with gains of 3q material with respect to the development of morphologic MDS and acute myeloid leukemia (AML). Thus, our data from 18 patients with 3q aberrations reveal that gains of 3q are strongly associated with a poor prognosis and represent an adverse risk factor in FA.

scholarly journals Knockdown of Fanconi anemia genes in human embryonic stem cells reveals early developmental defects in the hematopoietic lineage

Blood ◽  
2010 ◽  
Vol 115 (17) ◽  
pp. 3453-3462 ◽  
Author(s):  
Asmin Tulpule ◽  
M. William Lensch ◽  
Justine D. Miller ◽  
Karyn Austin ◽  
Alan D'Andrea ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Embryonic Stem Cells ◽  
Human Embryonic Stem Cells ◽  
Fanconi Anemia ◽  
Bone Marrow Failure ◽  
Embryonic Stem ◽  
Developmental Defects ◽  
Hematopoietic Development

Abstract Fanconi anemia (FA) is a genetically heterogeneous, autosomal recessive disorder characterized by pediatric bone marrow failure and congenital anomalies. The effect of FA gene deficiency on hematopoietic development in utero remains poorly described as mouse models of FA do not develop hematopoietic failure and such studies cannot be performed on patients. We have created a human-specific in vitro system to study early hematopoietic development in FA using a lentiviral RNA interference (RNAi) strategy in human embryonic stem cells (hESCs). We show that knockdown of FANCA and FANCD2 in hESCs leads to a reduction in hematopoietic fates and progenitor numbers that can be rescued by FA gene complementation. Our data indicate that hematopoiesis is impaired in FA from the earliest stages of development, suggesting that deficiencies in embryonic hematopoiesis may underlie the progression to bone marrow failure in FA. This work illustrates how hESCs can provide unique insights into human development and further our understanding of genetic disease.

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