Congenital thrombotic thrombocytopenic purpura in association with a mutation in the second CUB domain of ADAMTS13

Abstract

IntroductionThrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy characterized by a schistocytic hemolytic anemia and consumptive thrombocytopenia with varying degrees of neurologic and renal impairment. The presence of ultralarge von Willebrand factor (VWF) multimers in the plasmas of patients with chronic relapsing TTP during remission that disappear during an attack led to the implication of these multimers in the pathogenesis of the platelet-rich, fibrin-poor thrombi that occlude arterioles and are the hallmark of this disorder. 1 The VWF-cleaving metalloproteinase, ADAMTS13, hydrolyzes the ultralarge VWF multimers as they emerge from endothelial cells and undergo conformational strain due to shear stress in arterioles and capillaries. 2 A severe deficiency of VWF-cleaving proteinase activity is associated with the pathogenesis of congenital TTP (the SchulmanUpshaw syndrome). 3,4 A number of mutations, spread throughout the ADAMTS13 gene, have been reported in association with congenital TTP. 3,[5][6][7][8][9] The CUB domains at the C-terminus of ADAMTS13 are of uncertain physiologic relevance. The findings that the CUB domains are not required for VWF-cleaving proteinase activity measured under static conditions 10,11 and that certain strains of mice have a variant form of murine ADAMTS13 that lacks the CUB domains (together with the seventh and eighth thrombospondin type 1 (TSP-1) repeats) support the premise that these domains are dispensable in vivo. 12 However, a report that peptides from the CUB domains inhibit VWF-cleaving proteinase activity under flow, but not static, conditions suggests a functional role for these domains. 13 We studied a patient with congenital TTP who is a compound heterozygote for the Thr196Ile mutation in the metalloproteinase domain and the insertion of a nucleotide (A) at 4143-4144. This insertion results in a frameshift in the second CUB domain and loss of the last 49 amino acids of the protein. The CUB mutation had little effect on the specific activity of the enzyme but its secretion from COS-7 cells was impaired. Study design Case historyWe investigated an 8-year-old white girl with congenital TTP. Diagnosis was made when she was 18 months of age; she receives a plasma infusion every 2 to 3 months when her platelet count falls below 30 ϫ 10 9 /L. Assay of plasma VWF-cleaving proteinase activityAn assay based on the collagen-binding activity of digested VWF 14 was used to measure the VWF-cleaving proteinase activity in the plasma of the patient (during remission) and her family. ADAMTS13 sequence analysisDNA was extracted from peripheral blood leukocytes and all the exons and intron-exon boundaries of the ADAMTS13 gene were amplified by polymerase chain reaction (PCR) and sequenced. 5 The study was conducted with parental consent and institutional ethics approval. Transient expression of the ADAMTS13 mutantThe 4143insA mutant of the ADAMTS13 cDNA 15 was created using PCR-based mutagenesis. The wild-type and mutant constructs were subcloned into the mam...

Nonsense-mediated mRNA decay in the ADAMTS13 gene caused by a 29-nucleotide deletion

“…The defect may be due to the removal of the central β-strands present in the CUB domain, resulting in the destruction of its architecture, as previously described by Pimanda. 18 Eight different mutations in the first and second CUB domain were reported previously and some were analyzed by in vitro-expression studies, suggesting, consistently with our results, that the CUB domains play a critical role in the biosynthesis and secretion of ADAMTS13. 8,35,36 The 4143_4144insA mutation has been frequently detected in patients with hereditary ADAMTS13 deficiency in northern and central European countries.…”

“…[15][16][17][18][19] The present study evaluates the molecular mechanism of two mutations observed in the compound heterozygous state in two Turkish siblings with congenital TTP. One mutation, present on the maternal allele, is a single base (A) insertion mutation located within exon 29 (c.4143_4144insA) in the second CUB domain, leading to a frameshift and loss of the last 49 amino acids of the protein.…”

ADAMTS13 gene variants and function in women with preeclampsia: A population- based nested case- control study from the HUNT Study

“…Most of the reported mutations are limited to individual families, with two exceptions: 1) Mutation c.4143_4144dupA, where the insertion of a single base (adenine, A) at position 4143_4144 results in a frameshift and loss of 49 amino acids is one of the most frequently reported ADAMTS13 mutations in Caucasians [17][18][19][20][21][22][23] and therefore included in this study. 2) Mutation c.3178C>T (p.Arg1060Trp) in exon 24 is also frequent and associated with late-onset and pregnancy related TTP, and is therefore of special interest in relation to preeclampsia [24,25].…”

Effect of plasma exchange on plasma ADAMTS13 metalloprotease activity, inhibitor level, and clinical outcome in patients with idiopathic and nonidiopathic thrombotic thrombocytopenic purpura

“…[21][22][23] The cleavage can be stimulated by shear forces like those occurring at sites of arterial thrombosis or by low ionic strength and 1.5 M urea or guanidine. 19,20 Congenital ADAMTS13 deficiency is rare and associated with missense or frame-shift mutations of the ADAMTS13 gene, 18,[24][25][26][27][28][29] whereas acquired ADAMTS13 deficiency is more common and often caused by immunoglobulin G (IgG) inhibitors. 13,[30][31][32][33] Therefore, the efficacy of plasma infusion or therapeutic plasma exchange probably depends on replenishing the missing ADAMTS13 metalloprotease or removing the inhibitory antibodies.…”