Variant identification underlying inherited dysfibrinogenemia quite exceptionally fails. We report on two dysfibrinogenemia cases whose underlying DNA variant could not be identified by Sanger ...analysis. These failures result from two distinct mechanisms. The first case involved raw signal overcorrection by a built-in software, and the second constituted the first description of mosaicism for one of the fibrinogen genes. This mosaicism was subsequently identified by next-generation sequencing reanalysis of the sample.
Detrimental inflammation of the lungs is a hallmark of severe influenza virus infections. Endothelial cells are the source of cytokine amplification, although mechanisms underlying this process are ...unknown. Here, using combined pharmacological and gene-deletion approaches, we show that plasminogen controls lung inflammation and pathogenesis of infections with influenza A/PR/8/34, highly pathogenic H5N1 and 2009 pandemic H1N1 viruses. Reduction of virus replication was not responsible for the observed effect. However, pharmacological depletion of fibrinogen, the main target of plasminogen reversed disease resistance of plasminogen-deficient mice or mice treated with an inhibitor of plasminogen-mediated fibrinolysis. Therefore, plasminogen contributes to the deleterious inflammation of the lungs and local fibrin clot formation may be implicated in host defense against influenza virus infections. Our studies suggest that the hemostatic system might be explored for novel treatments against influenza.
Analyses of site-directed fibrinogen mutants expressed in several recombinant models have previously shown that both inter- and intra-chain disulfide bonds are critical for fibrinogen assembly and ...secretion. Four naturally occurring mutations on AαCys36 and AαCys45 residues are reported here to be associated with decreased fibrinogen levels. This confirms the main role of the AαCys36-BβCys65 and AαCys45-γCys23 disulfide bonds in reaching a normal fibrinogen plasma level. Decreased coagulant/antigen ratios indicate abnormal species secretion in heterozygous subjects which varies between individuals. However, in contrast to overexpression in experimental models, disruption of the AαCys36-BβCys65 disulfide bond did not result in the appearance of Aα-Bβ-γ moieties
in vivo
. A 188 kDa molecule reacting only with anti Aα and anti Bβ chains was found in the plasma of the AαCys45Tyr variant. Heterozygous carriers of Aα chain mutations usually have normal fibrinogen levels, in contrast to the AαCys36Gly, AαCys36Arg and AαCys45Tyr variants that are shown here to cause hypofibrinogenemia.
Numerous mutations in
,
or
lead to congenital fibrinogen disorders (CFDs), but their epidemiology is not well characterized. The aim of this study was to evaluate the molecular epidemiology of CFD ...and to develop a genotyping strategy.
Genetic data from 266 unrelated CFD patients genotyped at our laboratory and from a CFD open access database (
= 1,142) were evaluated. We developed a step-wise screening strategy for the molecular diagnosis of CFD and prospectively tested this strategy on 32 consecutive CFD probands.
We identified 345 mutated alleles overall, among 187 heterozygous, 63 homozygous and 16 compound heterozygous individuals. Afibrinogenemia was almost always caused by null mutations (98.6%), mainly in
(85%). Hypofibrinogenemia was mainly caused by missense mutations of
or
(54.2%). Dysfibrinogenemia was almost always caused by heterozygous missense mutations (99.3%) in
and
. Hotspot mutations were prevalent among quantitative (33.1%) and qualitative fibrinogen disorders (71.1%). The mutational cluster at our laboratory was similar with that reported in the CFD open access database. The proposed step-wise genetic screening strategy proved efficient in both the development and validation samples for CFD: the screening of
exons 2, 4, 5 and
exon 8 and search for the 11 kb deletion of
led to the identification of approximately 80% of mutated alleles, including 15 new mutations.
The described molecular epidemiology of CFD is complex. The proposed step-wise genetic screening strategy may provide an efficient way to identify causative mutations analysing a minimal number of exons.
PDF
