Novel SLFN14 mutation associated with macrothrombocytopenia in a patient with severe haemorrhagic syndrome

BACKGROUND

Platelet-type bleeding disorder 20 (BDPLT20), as known as SLFN14-related thrombocytopenia, is a rare inherited thrombocytopenia (IT). Previously, only 5 heterozygous missense mutations in the SLFN14 gene have been reported.

METHODS

A comprehensive clinical and laboratory examination of a 17-year-old female patient with macrothrombocytopenia and severe mucocutaneous bleeding was performed. Examination was carried out using standardized questionnaires to assess bleeding, high-throughput sequencing (Next Generation Sequencing), optical and fluorescence microscopy, flow cytometry with activation and analysis of intracellular calcium signaling of platelets, light transmission aggregometry and thrombus growth in the flow chamber.

RESULTS

Analysis of the patient's genotype revealed a previously undescribed c.655 A > G (p.K219E) variant in the hotspot of the SLFN14 gene. Immunofluorescence and brightfield examination of platelets in the smear showed heterogeneity in cells size, including giant forms over 10 μm (normal size 1-5) in diameter, with vacuolization and diffuse distribution of β₁-tubulin and CD63. Activated platelets showed impaired contraction and shedding/internalization of GPIb. GP IIb/IIIa clustering was increased at rest and attenuated upon activation. Intracellular signalling study revealed impaired calcium mobilization upon TRAP 35.97 nM (reference range 180 ± 44) and CRP-XL 10.08 nM (56 ± 30) stimulation. Aggregation with ADP, collagen, TRAP, arachidonic acid and epinephrine was impaired in light transmission aggregometry; agglutination with ristocetin persisted. In the flow chamber with a shear rate of 400 s^-1 platelet adhesion to collagen and clot growth were impaired.

CONCLUSION

The revealed disorders of phenotype, cytoskeleton and intracellular signaling explain the nature of SLFN14 platelet dysfunction and the patient's severe hemorrhagic syndrome.

Experimentally Validated Novel Factor XIIa Inhibitors Identified by Docking and Quantum Chemical Post-processing

Antithrombotic agents based on factor XIIa inhibitors can become a new class of drugs to manage conditions associated with thrombosis. Herein, we report identification of two novel classes of factor XIIa inhibitors. The first one is triazolopyrimidine derivatives designed on the basis of the literature aminotriazole hit and identified using virtual screening of the focused library. The second class is a spirocyclic furo[3,4-c]pyrrole derivatives identified by virtual screening of a large chemical library of drug-like compounds performed in a previous study but confirmed in vitro here. In both cases, the prediction of inhibitory activity is based on the score of the SOL docking program, which uses the MMFF94 force field to calculate the binding energy. For the best ligands selected in virtual screening of the large chemical library, postprocessing with the PM7 semiempirical quantum-chemical method was used to calculate the enthalpy of protein-ligand binding to prioritize 16 compounds for testing in enzymatic assay, and one of them demonstrated micromolar activity. For triazolopyrimidine library, 21 compounds were prioritized for the testing based on docking scores, and visual inspection of docking poses. Of these, 4 compounds showed inhibition of factor XIIa at 30 μM.

New Blood Coagulation Factor XIIa Inhibitors: Molecular Modeling, Synthesis, and Experimental Confirmation

In the modern world, complications caused by disorders in the blood coagulation system are found in almost all areas of medicine. Thus, the development of new, more advanced drugs that can prevent pathological conditions without disrupting normal hemostasis is an urgent task. The blood coagulation factor XIIa is one of the most promising therapeutic targets for the development of anticoagulants based on its inhibitors. The initial stage of drug development is directly related to computational methods of searching for a lead compound. In this study, docking followed by quantum chemical calculations was used to search for noncovalent low-molecular-weight factor XIIa inhibitors in a focused library of druglike compounds. As a result of the study, four low-molecular-weight compounds were experimentally confirmed as factor XIIa inhibitors. Selectivity testing revealed that two of the identified factor XIIa inhibitors were selective over the coagulation factors Xa and XIa.

Antigen-Specific Stimulation and Expansion of CAR-T Cells Using Membrane Vesicles as Target Cell Surrogates

Development of CAR-T therapy led to immediate success in the treatment of B cell leukemia. Manufacturing of therapy-competent functional CAR-T cells needs robust protocols for ex vivo/in vitro expansion of modified T-cells. This step is challenging, especially if non-viral low-efficiency delivery protocols are used to generate CAR-T cells. Modern protocols for CAR-T cell expansion are imperfect since non-specific stimulation results in rapid outgrowth of CAR-negative T cells, and removal of feeder cells from mixed cultures necessitates additional purification steps. To develop a specific and improved protocol for CAR-T cell expansion, cell-derived membrane vesicles are taken advantage of, and the simple structural demands of the CAR-antigen interaction. This novel approach is to make antigenic microcytospheres from common cell lines stably expressing surface-bound CAR antigens, and then use them for stimulation and expansion of CAR-T cells. The data presented in this article clearly demonstrate that this protocol produced antigen-specific vesicles with the capacity to induce stronger stimulation, proliferation, and functional activity of CAR-T cells than is possible with existing protocols. It is predicted that this new methodology will significantly advance the ability to obtain improved populations of functional CAR-T cells for therapy.