Publications by authors named "Simon Le Gallou"

16 Publications

  • Page 1 of 1

Circulating Myeloid Regulatory Cells: Promising Biomarkers in B-Cell Lymphomas.

Front Immunol 2020 2;11:623993. Epub 2021 Feb 2.

UMR_S_1236, Univ Rennes, Inserm, Rennes, France.

The monocyte/macrophage lineage has been shown to be involved in the promotion of a protumoral tumor microenvironment and resistance to treatment in B cell lymphomas. However, it is still poorly described at the single cell level, and tissue samples are not easily accessible. Thus, a detailed analysis of the circulating myeloid cell compartment in the different B lymphomas is needed to better understand the mechanisms of resistance to treatment and identify at risk patients. In this Perspective, we review current knowledge on the phenotypic and functional description of the circulating monocytic lineage in B cell lymphomas and provide first insights into the heterogeneity of these cell populations in health and lymphoma, using mass cytometry. Indeed, the monocytic compartment is a continuum more than distinct subpopulations, as demonstrated by our high-resolution approach, explaining the sometimes confusing and contradictory conclusions on the prognostic impact of the different populations, including monocytes and monocytic myeloid derived suppressor cells (M-MDSC). By identifying S100A9 monocytic cells as a potential biomarker in diffuse large B cell lymphoma (DLBCL) in this proof-of-concept preliminary study including a limited number of samples, we underline the potential of circulating myeloid regulatory cells as diagnostic and prognostic biomarkers in B-cell lymphomas.
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http://dx.doi.org/10.3389/fimmu.2020.623993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7884747PMC
February 2021

Linking the KIR phenotype with STAT3 and TET2 mutations to identify chronic lymphoproliferative disorders of NK cells.

Blood 2021 Jan 15. Epub 2021 Jan 15.

INSERM UMR1236,Rennes, France.

Distinguishing chronic lymphoproliferative disorders of NK cells (CLPD-NK) from reactive NK cell expansions is challenging. We assessed the value of NK receptor phenotyping and targeted high-throughput sequencing in a cohort of 114 consecutive patients with NK cell proliferation, retrospectively assigned to a CLPD-NK group (N=46) and a reactive NK group (N=68). We then developed a NK-clonality score combining flow cytometry and molecular profiling with a positive predictive value of 93%. STAT3 and TET2 mutations were respectively identified in 27% and 34% of the CLPD-NK patients - constituting a new diagnostic hallmark for this disease. TET2-mutated CLPD-NK exhibited preferentially a CD16low phenotype, displayed more frequently a lower platelet count, and were associated with other hematologic malignancies such as myelodysplasia. To explore the mutational clonal hierarchy of CLPD-NK, we performed a whole exome sequencing of sorted, myeloid, T, and NK cells and identified that TET2 mutations were shared by myeloid and NK cells in 3 out of 4 cases. Thus, we hypothesized that TET2 alterations occur early in CLPD-NK disease which could explain a potential link between NK-LGL leukemia and other myeloid malignancies. Finally, we analyzed the transcriptome by RNA-seq of 7 CLPD-NK and evidenced two groups of patients. The first group displayed STAT3 mutations or SOCS3 methylation and overexpressed STAT3 target genes. The second group, including two TET2-mutated cases, significantly under-expressed genes known to be down-regulated in angioimmunoblastic T-cell lymphoma. Our results provide new insights into the pathogenesis of NK cell proliferative disorders and potentially new therapeutic opportunities.
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http://dx.doi.org/10.1182/blood.2020006721DOI Listing
January 2021

SARS-CoV-2-Induced ARDS Associates with MDSC Expansion, Lymphocyte Dysfunction, and Arginine Shortage.

J Clin Immunol 2021 04 2;41(3):515-525. Epub 2021 Jan 2.

Infectious Diseases and Intensive Care Unit, Pontchaillou University Hospital, 2 rue Henri Le Guilloux, 35033, Rennes, France.

Purpose: The SARS-CoV-2 infection can lead to a severe acute respiratory distress syndrome (ARDS) with prolonged mechanical ventilation and high mortality rate. Interestingly, COVID-19-associated ARDS share biological and clinical features with sepsis-associated immunosuppression since lymphopenia and acquired infections associated with late mortality are frequently encountered. Mechanisms responsible for COVID-19-associated lymphopenia need to be explored since they could be responsible for delayed virus clearance and increased mortality rate among intensive care unit (ICU) patients.

Methods: A series of 26 clinically annotated COVID-19 patients were analyzed by thorough phenotypic and functional investigations at days 0, 4, and 7 after ICU admission.

Results: We revealed that, in the absence of any difference in demographic parameters nor medical history between the two groups, ARDS patients presented with an increased number of myeloid-derived suppressor cells (MDSC) and a decreased number of CD8 effector memory cell compared to patients hospitalized for COVID-19 moderate pneumonia. Interestingly, COVID-19-related MDSC expansion was directly correlated to lymphopenia and enhanced arginase activity. Lastly, T cell proliferative capacity in vitro was significantly reduced among COVID-19 patients and could be restored through arginine supplementation.

Conclusions: The present study reports a critical role for MDSC in COVID-19-associated ARDS. Our findings open the possibility of arginine supplementation as an adjuvant therapy for these ICU patients, aiming to reduce immunosuppression and help virus clearance, thereby decreasing the duration of mechanical ventilation, nosocomial infection acquisition, and mortality.
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http://dx.doi.org/10.1007/s10875-020-00920-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7775842PMC
April 2021

High-Dimensional Phenotyping of Human Myeloid-Derived Suppressor Cells/Tumor-Associated Macrophages in Tissue by Mass Cytometry.

Methods Mol Biol 2021 ;2236:57-66

Institut national de la santé et de la recherche médicale, Unité Mixte de Recherche U1236, Université Rennes 1, Etablissement Français du Sang Bretagne, Rennes, France.

Myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) are heterogeneous cells that share myeloid markers and are not easily distinguishable in human tumors due to their lack of specific markers. These cells are a major player in the tumor microenvironment and are involved in the prognosis and physiopathology of various tumors. Here is presented a scheme to decipher these cells by mass cytometry.
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http://dx.doi.org/10.1007/978-1-0716-1060-2_6DOI Listing
January 2021

Early-stage myeloid-derived suppressor cell count: Basophil exclusion matters.

J Allergy Clin Immunol 2019 10 3;144(4):1125-1127. Epub 2019 Jul 3.

INSERM, Rennes, France; Centre Hospitalier Universitaire de Rennes, Pôle Biologie, Rennes, France. Electronic address:

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http://dx.doi.org/10.1016/j.jaci.2019.06.027DOI Listing
October 2019

A splenic IgM memory subset with antibacterial specificities is sustained from persistent mucosal responses.

J Exp Med 2018 08 29;215(8):2035-2053. Epub 2018 Jun 29.

Team "Development of the Immune System," Institut Necker-Enfants Malades, Institut National de la Santé et de la Recherche Médicale U1151-Centre National de la Recherche Scientifique UMR 8253, Faculté de Médecine Paris Descartes, Université Paris Descartes, Sorbonne Paris Cité, Paris, France

To what extent immune responses against the gut flora are compartmentalized within mucosal tissues in homeostatic conditions remains a much-debated issue. We describe here, based on an inducible AID fate-mapping mouse model, that systemic memory B cell subsets, including mainly IgM B cells in spleen, together with IgA plasma cells in spleen and bone marrow, are generated in mice in the absence of deliberate immunization. While the IgA component appears dependent on the gut flora, IgM memory B cells are still generated in germ-free mice, albeit to a reduced extent. Clonal relationships and renewal kinetics after anti-CD20 treatment reveal that this long-lasting splenic population is mainly sustained by output of B cell clones persisting in mucosal germinal centers. IgM-secreting hybridomas established from splenic IgM memory B cells showed reactivity against various bacterial isolates and endogenous retroviruses. Ongoing activation of B cells in gut-associated lymphoid tissues thus generates a diversified systemic compartment showing long-lasting clonal persistence and protective capacity against systemic bacterial infections.
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http://dx.doi.org/10.1084/jem.20180977DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6080908PMC
August 2018

BAFF and CD4 T cells are major survival factors for long-lived splenic plasma cells in a B-cell-depletion context.

Blood 2018 04 29;131(14):1545-1555. Epub 2018 Jan 29.

Institut Necker-Enfants Malades-INSERM U1151/Centre National de la Recherche (CNRS) UMR8633, Université Paris Descartes, Faculté de Médecine, Paris, France.

Previous data have suggested that B-cell-depletion therapy may induce the settlement of autoreactive long-lived plasma cells (LLPCs) in the spleen of patients with autoimmune cytopenia. To investigate this process, we used the AID-CreERT2-EYFP mouse model to follow plasma cells (PCs) engaged in an immune response. Multiplex polymerase chain reaction at the single-cell level revealed that only a small fraction of splenic PCs had a long-lived signature, whereas PCs present after anti-CD20 antibody treatment appeared more mature, similar to bone marrow PCs. This observation suggested that, in addition to a process of selection, a maturation induced on B-cell depletion drove PCs toward a long-lived program. We showed that B-cell activating factor (BAFF) and CD4 T cells play a major role in the PC survival niche, because combining anti-CD20 with anti-BAFF or anti-CD4 antibody greatly reduce the number of splenic PCs. Similar results were obtained in the lupus-prone NZB/W model. These different contributions of soluble and cellular components of the PC niche in the spleen demonstrate that the LLPC expression profile is not cell intrinsic but largely depends on signals provided by the splenic microenvironment, implying that interfering with these components at the time of B-cell depletion might improve the response rate in autoimmune cytopenia.
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http://dx.doi.org/10.1182/blood-2017-06-789578DOI Listing
April 2018

The AID-Cre-ERT2 Model: A Tool for Monitoring B Cell Immune Responses and Generating Selective Hybridomas.

Methods Mol Biol 2017 ;1623:243-251

Institut Necker-Enfants Malades, INSERM U1151-CNRS UMR 8253, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine-Site Broussais, 14 Rue Maria Helena Vieira Da Silva, 75993, Paris Cedex 14, France.

Expression of activation-induced cytidine deaminase (AID) is the hallmark of B cells engaged in an immune response in germinal centers. We designed an inducible fate-mapping reporter mouse in which AID-expressing B cells could be timely and irreversibly marked, by knockin at the Aicda locus of a tamoxifen-inducible Cre recombinase. This mouse model allows notably for the long-term follow-up of memory B cells and plasma cells engaged in an immune response. We describe here a protocol to generate hybridomas from small memory subsets that can be easily traced and identified in this mouse line through Cre-activated fluorescent reporters.
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http://dx.doi.org/10.1007/978-1-4939-7095-7_19DOI Listing
March 2018

Mass cytometry deep phenotyping of human mononuclear phagocytes and myeloid-derived suppressor cells from human blood and bone marrow.

J Leukoc Biol 2017 08 11;102(2):437-447. Epub 2017 Apr 11.

Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA;

The monocyte phagocyte system (MPS) includes numerous monocyte, macrophage, and dendritic cell (DC) populations that are heterogeneous, both phenotypically and functionally. In this study, we sought to characterize those diverse MPS phenotypes with mass cytometry (CyTOF). To identify a deep phenotype of monocytes, macrophages, and DCs, a panel was designed to measure 38 identity, activation, and polarization markers, including CD14, CD16, HLA-DR, CD163, CD206, CD33, CD36, CD32, CD64, CD13, CD11b, CD11c, CD86, and CD274. MPS diversity was characterized for 1) circulating monocytes from healthy donors, 2) monocyte-derived macrophages further polarized in vitro (i.e., M-CSF, GM-CSF, IL-4, IL-10, IFN-γ, or LPS long-term stimulations), 3) monocyte-derived DCs, and 4) myeloid-derived suppressor cells (MDSCs), generated in vitro from bone marrow and/or peripheral blood. Known monocyte subsets were detected in peripheral blood to validate the panel and analysis pipeline. Then, using various culture conditions and stimuli before CyTOF analysis, we constructed a multidimensional framework for the MPS compartment, which was registered against historical M1 or M2 macrophages, monocyte subsets, and DCs. Notably, MDSCs generated in vitro from bone marrow expressed more S100A9 than when generated from peripheral blood. Finally, to test the approach in vivo, peripheral blood from patients with melanoma ( = 5) was characterized and observed to be enriched for MDSCs with a phenotype of CD14HLA-DRS100A9 (3% of PBMCs in healthy donors, 15.5% in patients with melanoma, < 0.02). In summary, mass cytometry comprehensively characterized phenotypes of human monocyte, MDSC, macrophage, and DC subpopulations in both in vitro models and patients.
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http://dx.doi.org/10.1189/jlb.5MA1116-457RDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6608074PMC
August 2017

Emergence of long-lived autoreactive plasma cells in the spleen of primary warm auto-immune hemolytic anemia patients treated with rituximab.

J Autoimmun 2015 Aug 23;62:22-30. Epub 2015 Jun 23.

Institut Necker-Enfants Malades, INSERM U1151-CNRS UMR 8253, Sorbonne Paris Cité, Université Paris Descartes, Faculté de Médecine-Site Broussais, Paris, France.

Primary warm autoimmune hemolytic anemia (wAIHA) is a rare autoimmune disease in which red blood cells are eliminated by IgG autoantibodies. We analyzed the antibody-secreting cells in the spleen and the peripheral blood of wAIHA patients in various contexts of treatment. Plasmablasts were observed in peripheral blood of newly diagnosed wAIHA patients and, accordingly, active germinal center reactions were present in the spleen of patients receiving short-term corticosteroid therapy. Long-term corticosteroid regimens markedly reduced this response while splenic plasma cells were able to persist, a fraction of them secreting anti-red blood cell IgG in vitro. In wAIHA patients treated by rituximab and who underwent splenectomy because of treatment failure, plasma cells were still present in the spleen, some of them being autoreactive. By using a set of diagnostic genes that allowed us to assess the plasma cell maturation stage, we observed that these cells displayed a long-lived program, differing from the one of plasma cells from healthy donors or from wAIHA patients with various immunosuppressant treatments, and more similar to the one of normal long-lived bone-marrow plasma cells. Interestingly, an increased level of B-cell activating factor (BAFF) was observed in the supernatant of spleen cell cultures from such rituximab-treated wAIHA patients. These results suggest, in line with our previous report on primary immune thrombocytopenia, that the B-cell depletion induced by rituximab promoted a suitable environment for the maturation and survival of auto-immune long-lived plasma cells in the spleen.
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http://dx.doi.org/10.1016/j.jaut.2015.05.006DOI Listing
August 2015

Multiple players in mouse B cell memory.

Curr Opin Immunol 2013 Jun 28;25(3):334-8. Epub 2013 May 28.

INSERM U783 Développement du système immunitaire, Université Paris Descartes, Faculté de Médecine, Site Broussais, 96 rue Didot, Paris, France.

B cell memory has long been considered the attribute of the sole IgG-positive B cell subset. Since a few years, and due to new B-cell subset identification procedures, increasing heterogeneity has been identified among the memory B cell pool. IgM-positive cells and germinal center-independent subsets are recent additions to the field. This review describes the diversity of memory B cells, as well as controversial issues on their relative contribution to the recall response. The impact of a protracted germinal center response to the specific mobilization of IgM memory B cells is proposed.
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http://dx.doi.org/10.1016/j.coi.2013.05.004DOI Listing
June 2013

B cell depletion in immune thrombocytopenia reveals splenic long-lived plasma cells.

J Clin Invest 2013 Jan 17;123(1):432-42. Epub 2012 Dec 17.

Faculté de Médecine, Site Necker-Enfants Malades, INSERM U783 Développement du système immunitaire, Université Paris Descartes, Paris, France.

Primary immune thrombocytopenia (ITP) is a disorder caused by autoantibody-mediated platelet destruction and decreased platelet production. Rituximab, a B cell-depleting agent, has become the first-line treatment for ITP; however, patients with refractory disease usually require splenectomy. We identified antibody-secreting cells as the major splenic B cell population that is resistant to rituximab. The phenotype, antibody specificity, and gene expression profile of these cells were characterized and compared to those of antibody-secreting cells from untreated ITP spleens and from healthy tissues. Antiplatelet-specific plasma cells (PC) were detected in the spleens of patients with ITP up to 6 months after rituximab treatment, and the PC population displayed a long-lived program similar to the one of bone marrow PC, thus explaining for most of these patients the absence of response to rituximab and the response to splenectomy. When analyzed by multiplex PCR at the single-cell level, normal splenic PC showed a markedly different gene expression profile, with an intermediate signature, including genes characteristic of both long-lived PC and proliferating plasmablasts. Surprisingly, long-lived PC were not detected in untreated ITP spleens. These results suggest that the milieu generated by B cell depletion promotes the differentiation and settlement of long-lived PC in the spleen.
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http://dx.doi.org/10.1172/JCI65689DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3533302PMC
January 2013

IL-2 requirement for human plasma cell generation: coupling differentiation and proliferation by enhancing MAPK-ERK signaling.

J Immunol 2012 Jul 25;189(1):161-73. Epub 2012 May 25.

INSERM, Unité Mixte de Recherche 917, Rennes F-35043, France.

Mature B cell differentiation involves a well-established transcription factor cascade. However, the temporal dynamics of cell signaling pathways regulating transcription factor network and coordinating cell proliferation and differentiation remain poorly defined. To gain insight into the molecular processes and extrinsic cues required for B cell differentiation, we set up a controlled primary culture system to differentiate human naive B cells into plasma cells (PCs). We identified T cell-produced IL-2 to be critically involved in ERK1/2-triggered PC differentiation. IL-2 drove activated B cell differentiation toward PC independently of its proliferation and survival functions. Indeed, IL-2 potentiated ERK activation and subsequent BACH2 and IRF8 downregulation, sustaining BLIMP1 expression, the master regulator for PC differentiation. Inhibition of the MAPK-ERK pathway, unlike STAT5 signaling, impaired IL-2-induced PC differentiation and rescued the expression profile of BACH2 and IRF8. These results identify IL-2 as a crucial early input in mature B cell fate commitment.
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http://dx.doi.org/10.4049/jimmunol.1200301DOI Listing
July 2012

Characterization of a transitional preplasmablast population in the process of human B cell to plasma cell differentiation.

J Immunol 2011 Oct 14;187(8):3931-41. Epub 2011 Sep 14.

INSERM, Unité 1040, 34000 Montpellier, France.

The early steps of differentiation of human B cells into plasma cells are poorly known. We report a transitional population of CD20(low/-)CD38(-) preplasmablasts along differentiation of human memory B cells into plasma cells in vitro. Preplasmablasts lack documented B cell or plasma cell (CD20, CD38, and CD138) markers, express CD30 and IL-6R, and secrete Igs at a weaker level than do plasmablasts or plasma cells. These preplasmablasts further differentiate into CD20(-)CD38(high)CD138(-) plasmablasts and then CD20(-)CD38(high)CD138(+) plasma cells. Preplasmablasts were fully characterized in terms of whole genome transcriptome profiling and phenotype. Preplasmablasts coexpress B and plasma cell transcription factors, but at a reduced level compared with B cells, plasmablasts, or plasma cells. They express the unspliced form of XBP1 mRNA mainly, whereas plasmablasts and plasma cells express essentially the spliced form. An in vivo counterpart (CD19(+)CD20(low/-)CD38(-)IL-6R(+) cells) of in vitro-generated preplasmablasts could be detected in human lymph nodes (0.06% of CD19(+) cells) and tonsils (0.05% of CD19(+) cells). An open access "B to Plasma Cell Atlas," which makes it possible to interrogate gene expression in the process of B cell to plasma cell differentiation, is provided. Taken together, our findings show the existence of a transitional preplasmablast population using an in vitro model of plasma cell generation and of its in vivo counterpart in various lymphoid tissues.
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http://dx.doi.org/10.4049/jimmunol.1101230DOI Listing
October 2011

CXCR4 expression functionally discriminates centroblasts versus centrocytes within human germinal center B cells.

J Immunol 2009 Jun;182(12):7595-602

Unité 917, Faculté de Médecine, Institut National de la Santé et de la Recherche Médicale, Université Rennes 1, Rennes, France.

The human germinal center is a highly dynamic structure where B cells conduct their terminal differentiation and traffic following chemokine gradients. The rapidly dividing centroblasts and the nondividing centrocytes represent the two major B cell subsets present in germinal center and also the most common normal counterparts for a majority of lymphomas. CD77 expression was previously associated to proliferating centroblasts undergoing somatic hypermutation, but data from transcriptional studies demonstrate that CD77 is not a reliable marker to discriminate human centroblasts from centrocytes. Herein we were able for the first time to separate these two subpopulations based on the expression of the chemokine receptor CXCR4 allowing their characterization. Phenotypic and functional features were especially explored, giving an accurate definition of CXCR4(+) centroblasts compared with CXCR4(-) centrocytes. We show that CXCR4(+) and CXCR4(-) germinal center B cells present a clear dichotomy in terms of proliferation, transcription factor expression, Ig production, and somatic hypermutation regulation. Microarray analysis identified an extensive gene list segregating these B cells, including highly relevant genes according to previous knowledge. By gene set enrichment analysis we demonstrated that the centroblastic gene expression signature was significantly enriched in Burkitt's lymphomas. Collectively, our findings show that CXCR4 expression can properly separate human centroblasts from centrocytes and offer now the possibility to have purified normal counterparts of mature B cell-derived malignancies.
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http://dx.doi.org/10.4049/jimmunol.0804272DOI Listing
June 2009

MLPA screening reveals novel subtelomeric rearrangements in holoprosencephaly.

Hum Mutat 2007 Dec;28(12):1189-97

Institut de Génétique et Développement de Rennes, Université de Rennes1, Faculté de Médecine, Rennes, France.

Holoprosencephaly (HPE) is the most common developmental brain anomaly in human, associated with a wide spectrum of presentations. The etiology is heterogeneous, due to environmental and genetic factors. Out of 12 cytogenetic candidate loci previously reported, eight were subtelomeric, including the loci in which two of the four major HPE genes were identified (SHH and TGIF). Recently, we reported that these two genes could be mutated or microdeleted. Therefore, we hypothesized that subtelomeres screening in HPE patients could refine the known subtelomeric candidate loci and identify novel ones. In this study, 181 samples, 72 fetuses and 109 live-born infants, with HPE and a normal karyotype, and 10 patients deleted for SHH or TGIF (3.5 Mb from telomeres) were screened for subtelomeric rearrangements using the multiplex ligation probe-dependent amplification (MLPA) method with two kits. Quantitative PCR was performed when discrepancies were observed between these two kits. We found that known SHH and TGIF microdeletions on 7q and 18p, encompassed their subtelomeric region (3.5 Mb) and were often associated with cryptic gains. Out of the 181 samples, we detected rearrangements in known candidate HPE loci (1q, 20p, and 21q) as well as in other novel subtelomeric locations (1p, 5q, 8p, 17q, 18q, 22q, and Xq) and in the subcentromeric 15q. We also found associations between cryptic subtelomeric gain and loss that may be inherited from a parental balanced translocation, which is helpful for genetic counseling. These findings reinforce the multihit origin for HPE and contribute to the explanation of the wide phenotypic spectrum described in this developmental disorder.
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http://dx.doi.org/10.1002/humu.20594DOI Listing
December 2007