SPECTRUM OF ADAMTS13 GENE MUTATIONS IN 19 PATIENTS WITH ADAMTS13 DEFICIENCY

CALDERAZZO JC; KEMPFER AC; KELLER L; SÁNCHEZ-LUCEROS A; WOODS AI; POWAZNIAK Y; LAZZARI MA

Boston, USA

Congreso; XXII Congress of The International Society on Thrombosis and Haemostasis; 2009

International Society on Thrombosis and Haemostasis

The thrombotic thrombocytopenic purpura (PTT) is a microangiopathic disease associated with ADAMTS13 deficiency. ADAMTS13 mutations and polymorphisms have been reported in congenital PTT. These were found throughout the gene, in regions that code for different domains. In vitro studies have shown an essential role of the N-terminal region from the metalloprotease domain to the spacer domain on the VWF-cleavage. However, C-terminally truncated ADAMTS13 exhibited decreased activity in the cleavage of VWF under high shear rate (Banno, 2009). Our purpose was to perform the spectrum of described mutations and detect new mutations and polymorphisms in our patient population, to assess how they are clustered along the gene. We studied 19 patients (P) with thrombotic microangiopathy, all with ADAMTS13 deficiency (31±8% U/dL, normal range: 46-184% U/ dL). ADAMTS13 activity was evaluated as we described previously. Automated sequencing of PCR was performed on an ABI Prism 310 Analyzer. We sequenced exons: 3(P:17), 5(P:9), 6(P:9), 9(P:4), 12 (P:4), 15(P:8), 17-18(P:8), 20(P:10), 21(P:6), 24(P:7), 25(P:12), 26(P:3), 27(P:10), 28(P:10), y 29 (P:13). It was found in intron 2, a P homozygous for the new polymorphisms G173-18T and G173-48A (homozygous father and heterozygous mother with normal ADAMTS13 activity); in exon 6, a P homozygous for the C577T mutation; in exon 24, a P homozygous for the mutation T3178T (heterozygous father, normal ADAMTS13 activity); exon 25, a P heterozygous for the new mutation G3368A and in exon 29, a P homozygous for the new mutation A4085T. Exon 29 includes the domain CUB at the C-terminus of ADAMTS13 gene. This preliminary study allowed us to locate clusters of mutations in specific areas: domains near the N terminus (exons 3 and 6) and near the C-terminus (exons 24, 25 and 29). The levels of ADAMTS13 activity were not different among the two groups (34,37 and 42,37,22 U/dL).