Acquired uniparental disomy of chromosome 9p is a frequent stem cell defect in polycythemia vera

AbstractFamilial clustering of malignancies provides a unique opportunity to identify molecular causes of cancer. Polycythemia vera (PV) is a myeloproliferative disorder due to an unknown somatic stem cell defect that leads to clonal myeloid hyperproliferation. We studied 6 families with PV. The familial predisposition to PV appears to follow an autosomal dominant inheritance pattern with incomplete penetrance. All examined females informative for a transcriptional clonality assay had clonal hematopoiesis. We excluded linkage between PV and a number of previously proposed candidate disease loci (c-mpl, EPOR, 20q, 13q, 5q, 9p). Therefore, mutations at these loci are unlikely primary causes of familial PV. The finding of erythropoietin-independent erythroid progenitors in healthy family members indicated the presence of the PV stem cell clone in their hematopoiesis. This finding, together with clonal hematopoiesis in the affected individuals, supports the hypothesis of multiple genetic defects involved in the early pathogenesis of PV. (Blood. 2003;102:3793-3796)

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Loss of Heterozygosity on Chromosome 9p24 Is the Most Frequent Chromosomal Aberration in Polycythemia Vera and Idiopathic Myelofibrosis.

Blood ◽

10.1182/blood.v104.11.2425.2425 ◽

2004 ◽

Vol 104 (11) ◽

pp. 2425-2425

Author(s):

Robert Kralovics ◽

Francesco Passamonti ◽

Kun Liu ◽

Soon-Siong Teo ◽

Anthony Bench ◽

...

Keyword(s):

Polycythemia Vera ◽

Loss Of Heterozygosity ◽

Chromosomal Aberration ◽

Cytogenetic Analysis ◽

Uniparental Disomy ◽

Comparative Genomic ◽

Parental Origin ◽

Idiopathic Myelofibrosis ◽

Clonal Hematopoiesis ◽

Chromosome 9P

Abstract Myeloproliferative disorders (MPD) represent a heterogeneous group of diseases characterized by excessive myeloid cell production and clonal hematopoiesis. The appearance of the MPD stem cell clone is believed to be a consequence of an as yet unknown somatic mutation. The genetic basis for clonal hematopoiesis in MPD has been extensively studied using cytogenetic analysis, but no invariant chromosomal aberration has been found. Recently, we identified loss of heterozygosity of chromosome 9p (9pLOH) as a clonal defect in a small cohort of polycythemia vera (PV) patients. Here we extended this study to a total of 295 patients with MPD; 171 with PV, 91 with essential thrombocythemia (ET), and 33 with idiopathic myelofibrosis (IMF). The 9pLOH was detected in 62/171 patients with PV (36%) and in 10/33 patients with IMF (30%). Thus, 9pLOH is the most frequent chromosomal aberration in PV and IMF described to date. Interestingly, only 2/91 patients with the diagnosis of ET had 9pLOH. The reason for this difference is currently unknown and may be related to the presence of polyclonal hematopoiesis in a proportion of ET. By increasing the microsatellite marker density used for the LOH mapping in all 68 patients with 9pLOH, we identified a 6.2 Mbp minimal common LOH region. Copy number analysis performed by quantitative PCR revealed that all patients with 9pLOH had two copies of the chromosomal region involved in LOH. This finding excludes deletions as the genetic mechanism underlying 9pLOH and indicates that mitotic recombination is involved. This explains why this chromosomal defect remained hidden to cytogenetic analysis, FISH, or comparative genomic hybridization. 9pLOH results in partial uniparental disomy (UDP) of chromosome 9p. The phenotypic consequences of UPD are often associated with genes undergoing genomic imprinting. However, in two of our patients with 9pLOH, we were able to determine the parental origin of the lost chromosome by analyzing their parents. In one patient, the maternal chromosome was lost, whereas in the other patient, the paternal chromosome was missing. This variability of parental origin of UDP makes the involvement of imprinted genes in the expansion of the 9pLOH clone unlikely and favors a tumor suppressor mechanism. CDKN2A and CDKN2B genes (INK4A, INK4B), localized on 9p21, are among the most frequently mutated tumor suppressors in human malignancies. However, the CDKN2A/B locus is not part of the minimal 9pLOH region in MPD. The 6.2 Mbp common 9pLOH region contains 40 genes and ESTs. We determined which of these genes are expressed in hematopoietic cells and are currently sequencing the cDNAs of these genes to search for mutations.

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HMGA2, a Member of the High Mobility Group Gene Family, Is Expressed at the Protein Level in Peripheral Blood CD34+ Cells of Patients with Idiopathic Myelofibrosis and Polycythemia Vera.

Blood ◽

10.1182/blood.v104.11.798.798 ◽

2004 ◽

Vol 104 (11) ◽

pp. 798-798 ◽

Cited By ~ 2

Author(s):

Stephen Huang ◽

Minjiang Xu ◽

Edward Bruno ◽

Giovanni Barosi ◽

Josef Prchal ◽

...

Keyword(s):

Stem Cell ◽

Polycythemia Vera ◽

Hematopoietic Stem Cell ◽

Peripheral Blood ◽

High Mobility ◽

Idiopathic Myelofibrosis ◽

Hematopoietic Stem ◽

Cd34 Cells ◽

Hmga2 Protein ◽

Cell Defect

Idiopathic myelofibrosis (IM) is a chronic myeloproliferative disorder associated with increased numbers of CD34+ cells circulating in the peripheral blood (PB). To characterize these cells, we transplanted CD34+ or CD34− cells from either G-CSF mobilized PB or IM PB into NOD/SCID mice to test their hematopoietic stem cell function. IM CD34+ cells, but not CD34−, cells engrafted in NOD/SCID mice, demonstrating that IM PB CD34+ cells contain true bone marrow repopulating cells. Furthermore, the differentiation program of IM CD34+ cells was quite different than that of CD34+ cells isolated from normal donors receiving G-CSF. G-CSF mobilized PB CD34+ cells generated predominantly CD19+ cells (B-lymphocytes), while IM PB CD34+ cells generated predominantly myeloid cells as well as larger numbers of CD41+ cells (megakaryocytes), but few CD19+ cells. The molecular basis for this stem cell defect in IM remains poorly defined. We hypothesized that the High Mobility Group Gene, HMGA2, might play a role in the biogenesis of IM. HMGA2 is a nuclear protein, normally expressed only during embryonic and fetal development, which acts as an architectural transcription factor important in the growth and differentiation of cells of mesenchymal origin. It has been reported that this gene has a direct effect on chromatin configuration by promoting DNA relaxation and that it may control the transcriptional activities of several genes. Rearrangement of the HMGA2 gene has frequently been detected in human benign tumors of mesenchymal origin including lipomas and sarcomas. In addition, the gene has been shown to be overexpressed in squamous cell carcinomas of the oral cavity. Previous work has suggested that HMGA2 is overexpressed in the PB mononuclear cells of patients with IM at the mRNA level (Andrieux, J. et al, Genes, Chromosomes & Cancer, 39: 82, 2004). Since IM and polycythemia vera (PV) are hematological malignancies that originate at the level of the hematopoietic stem cell, we examined the expression of HMGA2 in CD34+ and CD34− cell fractions isolated from the PB of patients with IM and PV as well as G-CSF mobilized normal donors. Using Western Blotting, we were unable to detect HMGA2 protein in either G-CSF mobilized CD34+ or CD34− cells. By contrast, HMGA2 was clearly expressed in the CD34+ cell fraction, but not the CD34− fraction isolated from IM and PV patients. These data indicate that increased HMGA2 protein levels are unique to IM and PV CD34+ cells and that the aberrant expression of this gene in the CD34+ progenitor cells may contribute to the stem cell defect in these myeloproliferative disorders.

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Stem Cell Defect in Ubiquitin-Green Fluorescent Protein Mice Facilitates Engraftment of Lymphoid-Primed Hematopoietic Stem Cells

Stem Cells ◽

10.1002/stem.2828 ◽

2018 ◽

Vol 36 (8) ◽

pp. 1237-1248

Author(s):

Kateřina Faltusová ◽

Katarína Szikszai ◽

Martin Molík ◽

Jana Linhartová ◽

Petr Páral ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Green Fluorescent Protein ◽

Hematopoietic Stem Cells ◽

Fluorescent Protein ◽

Hematopoietic Stem ◽

Green Fluorescent ◽

Cell Defect

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Relapse of leukemia with loss of mismatched HLA resulting from uniparental disomy after haploidentical hematopoietic stem cell transplantation

Blood ◽

10.1182/blood-2009-11-254284 ◽

2010 ◽

Vol 115 (15) ◽

pp. 3158-3161 ◽

Cited By ~ 70

Author(s):

Itzel Bustos Villalobos ◽

Yoshiyuki Takahashi ◽

Yoshiki Akatsuka ◽

Hideki Muramatsu ◽

Nobuhiro Nishio ◽

...

Keyword(s):

Stem Cell ◽

Hematopoietic Stem Cell Transplantation ◽

Stem Cell Transplantation ◽

Cell Transplantation ◽

Hematopoietic Stem Cell ◽

Single Nucleotide Polymorphism Array ◽

Uniparental Disomy ◽

Leukemic Cells ◽

Hematopoietic Stem ◽

Hla Alleles

Abstract We investigated human leukocyte antigen (HLA) expression on leukemic cells derived from patients at diagnosis and relapse after hematopoietic stem cell transplantation (HSCT) using flow cytometry with locus-specific antibodies. Two of 3 patients who relapsed after HLA-haploidentical HSCT demonstrated loss of HLA alleles in leukemic cells at relapse; on the other hand, no loss of HLA alleles was seen in 6 patients who relapsed after HLA-identical HSCT. Single-nucleotide polymorphism array analyses of sorted leukemic cells further revealed the copy number-neutral loss of heterozygosity, namely, acquired uniparental disomy on the short arm of chromosome 6, resulting in the total loss of the mismatched HLA haplotype. These results suggest that the escape from immunosurveillance by the loss of mismatched HLA alleles may be a crucial mechanism of relapse after HLA-haploidentical HSCT. Accordingly, the status of mismatched HLA on relapsed leukemic cells should be checked before donor lymphocyte infusion.

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Possible Juvenile Myelocytic leukaemia in a child with NF1 – an underlying stem cell defect?

10.7244/cmj.2019.11.001 ◽

2019 ◽

Author(s):

Callum Fernando ◽

Anne Kelly

Keyword(s):

Stem Cell ◽

Myelocytic Leukaemia ◽

Cell Defect

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SNP Karyotyping Can Detect Clonality of Stem Cell Compartment and Early Malignant Evolution in Aplastic Anemia

Blood ◽

10.1182/blood.v112.11.443.443 ◽

2008 ◽

Vol 112 (11) ◽

pp. 443-443

Author(s):

Marcin Wlodarski ◽

Sanjay Mohan ◽

Lukasz Gondek ◽

Jungwon Huh ◽

Michael Clemente ◽

...

Keyword(s):

Stem Cell ◽

Aplastic Anemia ◽

Chromosomal Abnormalities ◽

Snp Array ◽

Uniparental Disomy ◽

Multiple Time ◽

Cell Compartment ◽

Monosomy 7 ◽

Stem Cell Compartment ◽

Trisomy 12

Abstract Aplastic anemia (AA) is characterized by pancytopenia due to contraction/destruction of stem cell compartment. Most investigators consider the presence of clonal cytogenetic abnormalities as incompatible with the AA diagnosis. Despite excellent response rates to immunosuppression (IS) in the majority of AA patients, clonal malignant evolution to myelodysplasia (MDS) can occur in 10–15% in 10 years. Among such cases monosomy 7 (mono7) is the most commonly reported cytogenetic abnormality. Routine metaphase cytogenetics (MC) depends upon high numbers of dividing cells with inducible mitosis and is therefore often noninformative in AA. The inability to early detect AA patients at risk for clonal evolution constitutes a significant clinical problem. We hypothesized that high resolution SNP-array technology (SNPA) that allows for the analysis of interphase genomes will improve detection of chromosomal abnormalities in MDS evolving from AA. In addition to MC, we applied Affymetrix chips to study whole genomes of AA patients (N=100; 69 and 67 were investigated using 50K/250K and 6.0 arrays, respectively; 25 patients were studied at multiple time points prior and post IS). Data was analyzed using CNAG v3.0 and Genotyping Console v2.0 and unbalanced lesions were detected, including regions of genomic gain, loss and copy number neutral loss of heterozygozity. Clonal malignant evolution was observed in 13 patients resulting in a conversion rate of 13%. We focused on longitudinal analysis of these patients. Abnormal endpoint MC was detected in a total of 69% of transformed patients (mono7 in 8/13, t(10;18)(q11.2;q21) in 1/13 and trisomy 12 in 1/13 patients, respectively). Remarkably in 5/13 (38%) of evolving AA patients, numerical aberrations were detected earlier by SNPA than MC. Mono7 (N=4) and trisomy 12 (N=1) were detected by SNPA in aspirates that showed normal or noninformative MC, while in subsequent analysis bone marrow exams concurred with the early diagnosis by SNPA. In 3 patients, MC and SNPA results were concordant and in 1 patient SNPA failed to early identify mono7,. Acquired uniparental disomy of various chromosomes was detected in a total of 4 patients and the analysis of nonmyeloid CD3+ cells revealed somatic nature of these lesions: 7q31.31–31.33(4.9mb), 17q11.2-qter(56mb), 6p12.1-pter(56mb) and 3q12.2-qter(97mb). Interestingly, 2 patients with UPD had normal concurrent MC and the clonal lesions were detected before clinical diagnosis of MDS was established. It is likely that depletion of stem cell compartment might favor detection of pseudoclonality manifested as non-pathogenic random chromosomal lesions. In our cohort, in 2 AA patients with normal MC, SNPA analysis prior to IS therapy revealed clonal UPD as confirmed by comparison of myeloid lineage with germ line configuration in CD3+ cells. These lesions disappeared post IS in both patients and nearly 2 years later a newly recruited pathogenic clone with mono7 was detected as a sole abnormality by SNPA and MC. These patients are very illustrative as they may point towards genomic instability as well as depletion of available stem cell pool resulting in frequent recruitment of defective SC. Our study demonstrates that SNPA is a powerful tool to early identify AA patients harboring clonal defects consistent with the diagnosis of MDS, and thus it potentially might have strong clinical implications.

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