One of the most common and unwanted side effects during oral anticoagulant therapy (OAT) is bleeding complications. In rare cases, vitamin K antagonist (VKA)-related bleeding events are associated ...with mutations affecting the
F9
propeptide at amino acid position 37 due to a substitution of alanine to either valine or threonine. Based on our actual cohort of 18 patients, we update the knowledge on this rare phenotype and its origin. A founder mutation for both variants was reconfirmed by haplotype analysis of intronic and extragenic short tandem repeat (STR) polymorphisms with a higher prevalence in Switzerland than in other regions of Europe. Screening of healthy individuals for the presence of these
F9
gene mutations did not identify any of these variants, thus proving the rare occurrence of this genotype. Furthermore, both variants were expressed in vitro and warfarin dose responses were studied. Our warfarin dose response analysis confirmed higher sensitivity of both variants to warfarin with the effect being more apparent for Ala37Thr. Thus, although
F9
propeptide mutation-associated hypersensitivity to VKA is a rare phenomenon, awareness towards this bleeding phenotype is important to identify patients at risk.
Different endothelial cells share common features but also acquire organ specificity: for example the liver sinusoidal endothelial cells (LSECs) are major site of F8 secretion as compared to other ...endothelial cells. To decipher this specificity in LSECs and to understand the molecular mechanism of F8 synthesis and secretion, we have compared genome wide expression and epigenetic data of fetal LSECs (N=3) and non-liver endothelial cells (HCMEC, HPAEC, HPMEC and HUVEC; N=3), hepatocytes (N=3) and adult total blood (N=3). At a false discovery rate of <5% we found 4134 differentially methylated CpG sites and 663 differentially expressed probes (corresponding to 623 genes/loci) between LSECs and other endothelial cells. The loci were found by ingenuity pathway analysis (IPA) to be enriched in EIF2, eIF4, p7056K and mTOR signaling pathways together with LXR/RXR activation pathway. On the other hand, only 21 different loci and 152 CpGs were found to be statistically different (at <5% FDR) between hepatocytes and LSECs. According to IPA these were found enriched in interferon signaling, activation of IRF by cytosolic pattern recognition receptors and role of pattern recognition receptor in recognition of bacteria and viruses. Additionally, gene ontology analysis showed enrichment in GO-terms such as regulation of cellular metabolic process for LSECs vs. endothelial cells and blood vessel development, cell adhesion and regulation of cell migration for LSECs vs. hepatocytes. Moreover, in each of the GO sub categories of general coagulation (GO:0007596) and transcription factors (GO:003700) a small number of loci successfully differentially identify the LSECs from other endothelial cells. The above described results show specific molecular signature that characterize the F8 secreting cells and highlight specific cellular pathways associated with this process.
Oldenburg:SOBI: Consultancy.
Summary
The aim of molecular genetic analysis in families with haemophilia is to identify the causative mutation in an affected male as this provides valuable information for the patient and his ...relatives. For the patient, mutation identification may highlight inhibitor development risk or discrepancy between different factor VIII assays. For female relatives, knowledge of the familial mutation can facilitate carrier status determination and prenatal diagnosis. Recent advances in understanding mutations responsible for haemophilia and methods for their detection are presented. For reporting of such mutations, participation in external quality assessment ensures that essential patient and mutation details are routinely included and that pertinent information is incorporated in the interpretation.
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