Impact of genetic structural variants in factor XI deficiency: identification, accurate characterization, and inferred mechanism by long-read sequencing

BACKGROUND

Congenital factor XI (FXI) deficiency is a probably underestimated coagulopathy that confers antithrombotic protection. Characterization of genetic defects in F11 is mainly focused on the identification of single-nucleotide variants and small insertion/deletions because they represent up to 99% of the alterations accounting for factor deficiency, with only 3 gross gene defects of structural variants (SVs) having been described.

OBJECTIVES

To identify and characterize the SVs affecting F11.

METHODS

The study was performed in 93 unrelated subjects with FXI deficiency recruited in Spanish hospitals over a period of 25 years (1997-2022). F11 was analyzed by next-generation sequencing, multiplex ligand probe amplification, and long-read sequencing.

RESULTS

Our study identified 30 different genetic variants. Interestingly, we found 3 SVs, all heterozygous: a complex duplication affecting exons 8 and 9, a tandem duplication of exon 14, and a large deletion affecting the whole gene. Nucleotide resolution obtained by long-read sequencing revealed Alu repetitive elements involved in all breakpoints. The large deletion was probably generated de novo in the paternal allele during gametogenesis, and despite affecting 30 additional genes, no syndromic features were described.

CONCLUSION

SVs may account for a high proportion of F11 genetic defects implicated in the molecular pathology of congenital FXI deficiency. These SVs, likely caused by a nonallelic homologous recombination involving repetitive elements, are heterogeneous in both type and length and may be de novo. These data support the inclusion of methods to detect SVs in this disorder, with long-read-based methods being the most appropriate because they detect all SVs and achieve adequate nucleotide resolution.

Contact pathway in surgical and transcatheter aortic valve replacement

Background

Aortic valve replacement is the gold standard treatment for severe symptomatic aortic stenosis, but thrombosis of bioprosthetic valves (PVT) remains a concern.

Objective

To analyze the factors involved in the contact pathway during aortic valve replacement and to assess their impact on the development of thromboembolic complications.

Methods

The study was conducted in 232 consecutive patients who underwent: transcatheter aortic valve replacement (TAVR, N = 155), and surgical valve replacement (SAVR, N = 77) (MUVITAVI project). Demographic and clinical data, outcomes including a combined end point (CEP) of thrombotic events, and imaging controls were recruited. Samples were collected 24 h before and 48 h after valve replacement. FXII, FXI and (pre)kallikrein were evaluated by Western Blot and specific ELISA with nanobodies.

Results

The CEP of thrombotic events was reached by 19 patients: 13 patients presented systemic embolic events and 6 patients subclinical PVT. Valve replacement did not cause FXII activation or generation of kallikrein. There was a significant reduction of FXI levels associated with the procedure, which was statistically more pronounced in SAVR than in TAVR. Cases with reductions of FXI below 80% of basal values had a lower incidence of embolic events during the procedure than patients in whom FXI increased above 150%: 2.7 vs. 16.7%; p: 0.04.

Conclusion

TAVR or SAVR did not significantly activate the contact pathway. A significant reduction of FXI, was observed, particularly in SAVR, associated with lower incidence of thrombotic events. These results encourage evaluating the usefulness and safety of FXI-directed antithrombotic treatments in these patients.

Self-Consistent Mean Field Calculations of Polyelectrolyte-Surfactant Mixtures in Solution and upon Adsorption onto Negatively Charged Surfaces

Self-Consistent Mean-Field Calculations (SCF) have provided a semi-quantitative description of the physico-chemical behavior of six different polyelectrolyte-surfactant mixtures. The SCF calculations performed showed that both the formation of polymer-surfactant in bulk and the adsorption of the formed complexes onto negatively-charged surfaces are strongly affected by the specific nature of the considered systems, with the polymer-surfactant interactions playing a central role in the self-assembly of the complexes that, in turn, affects their adsorption onto interfaces and surfaces. This work evidences that SCF calculations are a valuable tool for deepening on the understanding of the complex physico-chemical behavior of polyelectrolyte-surfactant mixtures. However, it is worth noting that the framework obtained on the basis of an SCF approach considered an equilibrium situation which may, in some cases, be far from the real situation appearing in polyelectrolyte-surfactant systems.

Treatment charts in radiation therapy. An analysis of European treatment records

The radiotherapy treatment chart (dose prescription, set-up parameters, dose computation and daily dose recording form) represents an important working tool in radiotherapy, not only as a compilation of data, but also as a method of communication among physicians, physicists and technicians. In addition to administrative and medical data, physical and simulation data that are indispensable for the daily accurate reproduction of the therapy procedures should be recorded, as well as accurate daily entries of the fractional and cumulative absorbed doses. Moreover, any radiation therapy quality assurance programme must rely on the accessibility of the radiation treatment history and a correct record of the therapy protocol in order to be verifiable. We have analysed the treatment charts of 92 European Departments of Radiation Oncology, with the aim of identifying their salient characteristics and data recorded. The study shows strong differences among the charts analysed, not only in the amount of information recorded, but also in the kind of data and concepts used.

Dosimetry and use of an immobilization system for head and neck radiotherapy treatments

The day-to-day reproducibility of planned radiotherapy treatment is an important precondition for achieving good clinical results and reducing toxic effects. This reproducibility is difficult to achieve in the irradiation of head and neck malignancies because of the mobility of this anatomical area. This paper presents a dosimetric study and analysis of the utility of a facial mask immobilization system prepared from an orthopedic glass-fiber bandage. The dosimetric study conducted on a lucite phantom shows that the interposition of one, two, or three layers of the bandage reduces the deep absorbed dose by about 1% at 0.5 cm2, while increasing the absorbed surface dose by 12% (for a field of 15 X 15 cm2 and one layer of bandage) to 46% (for a field of 5 X 5 cm and three layers of bandage). The dosimetric study conducted on a Rando Anderson manikin shows an average increase in the skin dose of about 8% and a maximum increase of about 20%. The good dosimetric results and the practicality of this system of immobilization have persuaded us to propose it as an alternative to the systems currently on the market, which, although rather more sophisticated, are also more expensive.