TY  - JOUR
A1  - Manukjan, Georgi
A1  - Wiegering, Verena
A1  - Reindl, Tobias
A1  - Strauß, Gabriele
A1  - Klopocki, Eva
A1  - Schulze, Harald
A1  - Andres, Oliver
T1  - Novel variants in FERMT3 and RASGRP2 - Genetic linkage in Glanzmann-like bleeding disorders
JF  - Pediatric Blood & Cancer
N2  - 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.
KW  - bleding disorders other than hemophilia
KW  - hematology
KW  - hemostasis and thrombosis
KW  - platelet disorders
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208129
VL  - 67
IS  - 2
ER  - 
TY  - JOUR
A1  - Dirks, Johannes
A1  - Andres, Oliver
A1  - Paul, Luisa
A1  - Manukjan, Georgi
A1  - Schulze, Harald
A1  - Morbach, Henner
T1  - IgD shapes the pre-immune naïve B cell compartment in humans
JF  - Frontiers in Immunology
N2  - B cell maturation and immunoglobulin (Ig) repertoire selection are governed by expression of a functional B cell receptor (BCR). Naïve B cells co-express their BCR as IgM and IgD isotype. However, the role of the additionally expressed IgD on naïve B cells is not known. Here we assessed the impact of IgD on naïve 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 naïve 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 naïve B cell population lacking surface IgD expression. Flow cytometric analyses revealed a distinct phenotype of IgD-negative naïve 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 naïve B cell compartment as well as reduced frequencies of IgMlo/- B cells within the mature naïve 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 naïve B cell population. We conclude that IgD expression on human naïve B cells is redundant for generation of naïve 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/- naïve B cells known to be enriched in poly-/autoreactive B cell clones.
KW  - B cell
KW  - IgD
KW  - IgM
KW  - immunoglobulin repertoire
KW  - B cell maturation
KW  - B cell receptor
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304758
VL  - 14
ER  -