@article{DirksAndresPauletal.2023,
  author    = {Dirks, Johannes and Andres, Oliver and Paul, Luisa and Manukjan, Georgi and Schulze, Harald and Morbach, Henner},
  title     = {IgD shapes the pre-immune na{\"i}ve B cell compartment in humans},
  series = {Frontiers in Immunology},
  volume    = {14},
  journal   = {Frontiers in Immunology},
  doi       = {10.3389/fimmu.2023.1096019},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-304758},
  year      = {2023},
  abstract  = {B cell maturation and immunoglobulin (Ig) repertoire selection are governed by expression of a functional B cell receptor (BCR). Na{\"i}ve B cells co-express their BCR as IgM and IgD isotype. However, the role of the additionally expressed IgD on na{\"i}ve B cells is not known. Here we assessed the impact of IgD on na{\"i}ve B cell maturation and Ig repertoire selection in 8 individuals from 3 different families with heterozygous loss-of-function or loss-of expression mutations in IGHD. Although na{\"i}ve B cells from these individuals expressed IgM on their surface, the IGHD variant in heterozygous state entailed a chimeric situation by allelic exclusion with almost half of the na{\"i}ve B cell population lacking surface IgD expression. Flow cytometric analyses revealed a distinct phenotype of IgD-negative na{\"i}ve B cells with decreased expression of CD19, CD20 and CD21 as well as lower BAFF-R and integrin-β7 expression. IgD-negative B cells were less responsive in vitro after engaging the IgM-BCR, TLR7/9 or CD40 pathway. Additionally, a selective disadvantage of IgD-negative B cells within the T2 transitional and mature na{\"i}ve B cell compartment as well as reduced frequencies of IgMlo/- B cells within the mature na{\"i}ve B cell compartment lacking IgD were evident. RNA-Ig-seq of bulk sorted B cell populations showed an altered selection of distinct VH segments in the IgD-negative mature na{\"i}ve B cell population. We conclude that IgD expression on human na{\"i}ve B cells is redundant for generation of na{\"i}ve B cells in general, but further shapes the naive B cell compartment starting from T2 transitional B cells. Our observations suggest an unexpected role of IgD expression to be critical for selection of distinct Ig VH segments into the pre-immune Ig repertoire and for the survival of IgMlo/- na{\"i}ve B cells known to be enriched in poly-/autoreactive B cell clones.},
  language  = {en}
}
@article{CullmannJahnSpindleretal.2021,
  author    = {Cullmann, Katharina and Jahn, Magdalena and Spindler, Markus and Schenk, Franziska and Manukjan, Georgi and Mucci, Adele and Steinemann, Doris and Boller, Klaus and Schulze, Harald and Bender, Markus and Moritz, Thomas and Modlich, Ute},
  title     = {Forming megakaryocytes from murine-induced pluripotent stem cells by the inducible overexpression of supporting factors},
  series = {Research and Practice in Thrombosis and Haemostasis},
  volume    = {5},
  journal   = {Research and Practice in Thrombosis and Haemostasis},
  number    = {1},
  doi       = {10.1002/rth2.12453},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224565},
  pages     = {111 -- 124},
  year      = {2021},
  abstract  = {Background Platelets are small anucleate cells that circulate in the blood in a resting state but can be activated by external cues. In case of need, platelets from blood donors can be transfused. As an alternative source, platelets can be produced from induced pluripotent stem cells (iPSCs); however, recovered numbers are low. Objectives To optimize megakaryocyte (MK) and platelet output from murine iPSCs, we investigated overexpression of the transcription factors GATA-binding factor 1 (GATA1); nuclear factor, erythroid 2; and pre-B-cell leukemia transcription factor 1 (Pbx1) and a hyperactive variant of the small guanosine triphosphatase RhoA (RhoAhc). Methods To avoid off-target effects, we generated iPSCs carrying the reverse tetracycline-responsive transactivator M2 (rtTA-M2) in the Rosa26 locus and expressed the factors from Tet-inducible gammaretroviral vectors. Differentiation of iPSCs was initiated by embryoid body (EB) formation. After EB dissociation, early hematopoietic progenitors were enriched and cocultivated on OP9 feeder cells with thrombopoietin and stem cell factor to induce megakaryocyte (MK) differentiation. Results Overexpression of GATA1 and Pbx1 increased MK output 2- to 2.5-fold and allowed prolonged collection of MK. Cytologic and ultrastructural analyses identified typical MK with enlarged cells, multilobulated nuclei, granule structures, and an internal membrane system. However, GATA1 and Pbx1 expression did not improve MK maturation or platelet release, although in vitro-generated platelets were functional in spreading on fibrinogen or collagen-related peptide. Conclusion We demonstrate that the use of rtTA-M2 transgenic iPSCs transduced with Tet-inducible retroviral vectors allowed for gene expression at later time points during differentiation. With this strategy we could identify factors that increased in vitro MK production.},
  language  = {en}
}
@article{LauknerTruchetManukjanetal.2021,
  author    = {Laukner, Anna and Truchet, Laura and Manukjan, Georgi and Schulze, Harald and Langbein-Detsch, Ines and Mueller, Elisabeth and Leeb, Tosso and Kehl, Alexandra},
  title     = {Effects of cocoa genotypes on coat color, platelets and coagulation parameters in French Bulldogs},
  series = {Genes},
  volume    = {12},
  journal   = {Genes},
  number    = {7},
  issn      = {2073-4425},
  doi       = {10.3390/genes12071092},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242745},
  year      = {2021},
  abstract  = {A nonsense variant in HPS3, c.2420G>A or p.Trp807*, was recently discovered as the cause for a brown coat color termed cocoa in French Bulldogs. Here, we studied the genotype-phenotype correlation regarding coat color in HPS3 mutant dogs that carried various combinations of mutant alleles at other coat color genes. Different combinations of HPS3, MLPH and TYRP1 genotypes resulted in subtly different shades of brown coat colors. As HPS3 variants in humans cause the Hermansky-Pudlak syndrome type 3, which in addition to oculocutaneous albinism is characterized by a storage pool deficiency leading to bleeding tendency, we also investigated the phenotypic consequences of the HPS3 variant in French Bulldogs on hematological parameters. HPS3 mutant dogs had a significantly lowered platelet dense granules abundance. However, no increased bleeding tendencies in daily routine were reported by dog owners. We therefore conclude that in dogs, the phenotypic effect of the HPS3 variant is largely restricted to pigmentation. While an effect on platelet morphology is evident, we did not obtain any indications for major health problems associated with the cocoa coat color in French Bulldogs. Further studies will be necessary to definitely rule out very subtle effects on visual acuity or a clinically relevant bleeding disorder.},
  language  = {en}
}
@article{ManukjanWiegeringReindletal.2020,
  author    = {Manukjan, Georgi and Wiegering, Verena and Reindl, Tobias and Strauß, Gabriele and Klopocki, Eva and Schulze, Harald and Andres, Oliver},
  title     = {Novel variants in FERMT3 and RASGRP2 - Genetic linkage in Glanzmann-like bleeding disorders},
  series = {Pediatric Blood \& Cancer},
  volume    = {67},
  journal   = {Pediatric Blood \& Cancer},
  number    = {2},
  doi       = {10.1002/pbc.28078},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208129},
  pages     = {e28078},
  year      = {2020},
  abstract  = {Defects of platelet intracellular signaling can result in severe platelet dysfunction. Several mutations in each of the linked genes FERMT3 and RASGRP2 on chromosome 11 causing a Glanzmann-like bleeding phenotype have been identified so far. We report on novel variants in two unrelated pediatric patients with severe bleeding diathesis—one with leukocyte adhesion deficiency type III due to a homozygous frameshift in FERMT3 and the other with homozygous variants in both, FERMT3 and RASGRP2 . We focus on the challenging genetic and functional variant assessment and aim to accentuate the risk of obtaining misleading results due to the phenomenon of genetic linkage.},
  language  = {en}
}
@article{ManukjanRippergerVenturinietal.2016,
  author    = {Manukjan, Georgi and Ripperger, Tim and Venturini, Letizia and Stadler, Michael and G{\"o}hring, Gudrun and Schambach, Axel and Schlegelberger, Brigitte and Steinemann, Doris},
  title     = {GABP is necessary for stem/progenitor cell maintenance and myeloid differentiation in human hematopoiesis and chronic myeloid leukemia},
  series = {Stem Cell Research},
  volume    = {16},
  journal   = {Stem Cell Research},
  number    = {3},
  doi       = {10.1016/j.scr.2016.04.007},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168165},
  pages     = {677-681},
  year      = {2016},
  abstract  = {Maintenance of hematopoietic stem cells and their potential to give rise to progenitors of differentiated lymphoid and myeloid cells are accomplished by a network of regulatory processes. As a part of this network, the heteromeric transcription factor GA-binding protein (GABP) plays a crucial role in self-renewal of murine hematopoietic and leukemic stem cells. Here, we report the consequences of functional impairment of GABP in human hematopoietic and in leukemic stem/progenitor cells. Ectopic overexpression of a dominant-negative acting GABP mutant led to impaired myeloid differentiation of CD34\(^{+}\) hematopoietic stem/progenitor cells obtained from healthy donors. Moreover, drastically reduced clonogenic capacity of leukemic stem/progenitor cells isolated from bone marrow aspirates of chronic myeloid leukemia (CML) patients underlines the importance of GABP on stem/progenitor cell maintenance and confirms the relevance of GABP for human myelopoiesis in healthy and diseased states.},
  language  = {en}
}