Identification of genetic defects underlying FVII deficiency in 10 patients belonging to eight unrelated families of the North provinces from Tunisia

Genetic Landscape of Factor VII Deficiency: Insights from a Comprehensive Analysis of Pathogenic Variants and Their Impact on Coagulation Activity

Congenital factor VII (FVII) deficiency is a rare genetic bleeding disorder characterized by deficient or reduced activity of coagulation FVII. It is caused by genetic variants in the F7 gene. We aimed to evaluate the rate of detection of pathogenic variants in the F7 gene in a large group of patients with FVII deficiency and investigate the correlations between the F7 genotype and FVII activity (FVII:C). Moreover, the influence of the common genetic variant rs6046: c.1238G>A; p.(Arg413Gln), designated as the M2 allele, on FVII:C was investigated. Genetic analysis of the F7 gene was performed on 704 index patients (IPs) using either direct Sanger- or next-generation sequencing. Genetic variants were detected in 390 IPs, yielding a variant detection rate (VDR) of 55%. Notably, the VDR exhibited a linear decline with increasing FVII:C levels. We identified 124 genetic variants, of which 48 were not previously reported. Overall, the frequency of the M2 allele was considerably higher in patients with mild deficiency (FVII:C > 20 IU/dl). Furthermore, IPs lacking an identified pathogenic variant exhibited a significantly higher prevalence of the M2 allele (69%) compared to IPs with a disease-causing variant (47%). These results strongly support the association of the M2 allele with decreased FVII:C levels. This study shows the utility of FVII:C as a predictive marker for identifying pathogenic variants in patients with FVII deficiency. The M2 allele contributes to the reduction of FVII:C levels, particularly in cases of mild deficiency.

Clinical phenotype and F7 gene genotype in 40 Tunisian patients with congenital factor VII deficiency

Congenital factor VII (FVII) deficiency is an autosomal recessive bleeding disorder characterized by a weak phenotypic and genotypic correlation. This study aimed to determine the genetic alterations of 40 Tunisian patients and to evaluate their relationships with the collected clinical and biological data. Forty FVII-deficient Tunisian patients have been included in this study. First, diagnosis of the FVII deficiency was made on the basis of FVII coagulant activity (FVII:c) levels performed using the prothrombin time assay. Then, clinical and anamnesis data were set up and filed out from the regional registry of bleeding disorders and the medical file of each patient. Finally, genetic alterations were determined by direct sequencing of the coding regions, intron/exons boundaries of the F7 gene. Clinical heterogeneity was noticed, and the direct sequencing allowed the identification of 13 F7 gene mutations of which one was a novel mutation. The clinical manifestations are variably associated with FVII activity FVII:c levels. Lack of relations between severity of clinical manifestations and genotypes was observed; however, a relationship between the nonpathogeneous mutations and clinical phenotypes was noticed. A wide phenotypic inter-individual variability was detected, which suggests the presence of other extra-genetic components influencing the expressivity of the deficiency.

A novel factor X mutation Cys81 by Arg and a reported factor VII polymorphism Arg353 replaced by Gln co-occured in a patient

: Coagulation factor X and factor VII (FVII) are both very important components in blood coagulation. To study the molecular pathogenic mechanism of the inherited factor X and FVII deficiency, the factor X activity (FX:C) and FVII activity were tested with one-stage clotting methods. The factor X antigen and factor FVII antigen were tested with ELISA. All the exons, intron-exon boundaries and 5',3'-flanking regions of F10 and F7 genes were amplified by PCR with direct sequencing. The ClustalX software was used to analyze the conservative property of the mutation sites. The PolyPhen-2 and Sorting Intolerant From Tolerant (SIFT) online bioinformatics softwares were taken to predict whether the point mutation could affect protein function. The software Swiss-pdb Viewer was brought to analyze the impact of mutations on the structure and function of the protein. The thrombin generation tests were applied to evaluate whether there were obstacles in producing thrombin about the mutant protein. The FX:C and FVII activity of the proband were reduced to 35 and 42%, and the factor X antigen and factor FVII antigen were decreased to 43 and 55%, simultaneously. Correspondingly, a FX:Cys81Arg (Cys81 by Arg) mutation and a FVII:Arg353 replaced by Gln polymorphism were detected in the proband. The Cys81 of factor X was conserved among homologous species, but the Arg353 of FVII was not. All softwares analysis results indicated protein features and structures might be affected by the mutation and the polymorphism. And the thrombin generation tests showed that the mutant protein had obstacles in thrombin generation. We identified a FX:Cys81Arg mutation and a FVII:Arg353 replaced by Gln polymorphism in the proband. And they accounted for the decrease of the activity and antigen of factor X and FVII. Of note, the Cys81Arg of factor X was first reported in the world.

The Glanzmann's Thrombasthenia in Tunisia: A Cohort Study

Background

The Glanzmann’s thrombasthenia (GT) is a rare autosomal-recessive bleeding disorder with uncommon neonatal revelation. It is due to abnormalities of quantitative and/or qualitative α_IIbβ₃ integrin. This cell adhesion receptor is essential for platelet aggregation and allows the formation of a hemostatic plug if the vessel is damaged by injury. The clinical picture of GT is variable, with mucocutaneous bleeding due to non-functional platelets. Management requires a good expertise in bleeding disorders. We describe the clinical and the epidemiological data of GT in Aziza Othmana Hospital Hemophilia Center.

Methods

This was a retrospective study of all patients with GT monitored and treated in our hemophilia center during the period of 2011 - 2015.

Results

Twenty-seven patients among the 35 patients included in our hemophilia center registry were studied. The most common sign encountered is the gingival bleeding. In our women cohort, one completed her pregnancy. The consanguinity is present with a frequency of 62%. Treatments used depending on the case are tranexamic acid, platelet transfusion, packed red blood cells and rFVIIa, respectively.

Conclusion

GT is relatively frequent in Tunisia and especially in the North of the country which can be explained by the high consanguinity in our population.

F7 gene variants modulate protein levels in a large cohort of patients with factor VII deficiency. Results from a genotype-phenotype study

Congenital factor VII (FVII) deficiency is a rare bleeding disorder caused by mutations in F7 gene with autosomal recessive inheritance. A clinical heterogeneity with poor correlation with FVII:C levels has been described. It was the objective of this study to identify genetic defects and to evaluate their relationships with phenotype in a large cohort of patients with FVII:C<50 %. One hundred twenty-three probands were genotyped for F7 mutations and three polymorphic variants and classified according to recently published clinical scores. Forty out of 123 patients (33 %) were symptomatic (43 bleedings). A severe bleeding tendency was observed only in patients with FVII:C<0.10 %. Epistaxis (11 %) and menorrhagia (32 % of females in fertile age) were the most frequent bleedings. Molecular analysis detected 48 mutations, 20 not reported in the F7 international databases. Most mutations (62 %) were missense, large deletions were 6.2 %. Compound heterozygotes/homozygotes for mutations presented lower FVII:C levels compared to the other classes (Chi2=43.709, p<0,001). The polymorphisms distribution was significantly different among the three F7 genotypic groups (Chi2=72.289, p<0,001). The presence of truncating mutations was associated with lowest FVII:C levels (Chi2=21.351, p=0.002). This study confirms the clinical and molecular variability of the disease and the type of symptoms. It shows a good correlation between the type of F7 mutation and/or polymorphisms and FVII:C levels, without a direct link between FVII:C and bleeding tendency. The results suggest that large deletions are underestimated and that they represent a common mechanism of F7 gene inactivation which should always be investigated in the diagnostic testing for FVII deficiency.