Multiple in silico tools predict phenotypic manifestations in congenital thrombotic thrombocytopenic purpura

Abstract

SummaryCongenital thrombotic thrombocytopenic purpura (cTTP) is a rare, recessively inherited genetic disorder with varying clinical presentation that is caused by ADAMTS13 mutations. Several studies have found limited associations between ADAMTS13 mutations and cTTP phenotype. The use of in silico tools that examine multiple mutation characteristics may better predict phenotype. We analysed 118 ADAMTS13 mutations found in 144 cTTP patients reported in the literature and examined associations of several mutation characteristics, including N-terminal proximity, the evolutionary conservation of the affected amino acid position, as well as amino acid charge/phosphorylation and genetic codon usage to disease phenotype. Structure-altering mutations were examined for their impact on ADAM-TS13 function based on existing ADAMTS13 crystallographic data (AA 77-685). Our in silico data indicate that: (i) The position of the mutation in the N-or C-terminus, (ii) evolutionary conservation and (iii) codon usage of the affected mutation position are associated with disease parameters, such as age of onset, organ damage and fresh frozen plasma prophylaxis. In conclusion, the usage of multiple in silico tools presents a promising strategy in refining predictions for the diverse presentation of cTTP. Enhancing our utilization of in silico tools to find genotype-phenotype associations will create better-tailored approaches for individual patient treatment.

Combined study of ADAMTS13 and complement genes in the diagnosis of thrombotic microangiopathies using next‐generation sequencing

“…After acute episodes in the 4 TTP patients who had an ADAMTS13 rare variant and anti‐ADAMTS13 IgG antibodies, antibody levels returned to normal and ADAMTS13 activity increased to median 37.5% (range 35‐38), and this could be explained by their heterozygosity. Two variants carried by these patients, p.Pro457Leu and p.Arg1096His, were previously found to be associated with acquired ADAMTS13 deficiency . Expression studies revealed reduced ADAMTS13 secretion, and it was suggested that increased intracellular degradation promoted autoantibody production .…”

Treatment of Congenital Thrombotic Thrombocytopenic Purpura With Eculizumab

“…During the acute phase and also in remission, measurement of ADAMTS13 activity (in citrated plasma) showed undetectable levels (,6% using a collagen-binding assay and ,3% by fluorescence resonance energy transfer [FRET] using the ADAMTS13 fluorogenic substrate FRETS-rVWF73), 13 without evidence of inhibitory autoantibodies. By sequencing ADAMTS13, we found 2 heterozygous mutations (a guanine to adenine change at nucleotide 3,251 of the complementary DNA, which is predicted to cause a cysteine to tyrosine substitution at amino acid 1,084, and has been previously reported in patients with TTP, [14][15][16] and a previously unpublished frameshift [from deletion of the cytosine at nucleotide 4,049 of the complementary DNA] after the arginine at amino acid 1,351, which is predicted to lead to a premature stop codon 9 amino acids later, Fig S5). Taken together, screening results were consistent with a diagnosis of congenital TTP.…”

Pediatric thrombotic thrombocytopenic purpura

“…Family consanguinity should be investigated in congenital TTP patients. Moreover, in vitro and in silico studies of ADAMTS13 sequence variations have confirmed the deleterious effect of some mutations on the function of ADAMTS13 or on the impairment of its secretion …”