Antithrombin (AT) is an important anticoagulant in hemostasis. We describe here the characterization of a novel AT mutation associated with clinically relevant thrombosis. A pair of sisters with confirmed type I AT protein deficiency was genetically analyzed on suspicion of an inherited SERPINC1 mutation. A frameshift mutation, c.1247dupC, was identified and the effect of this mutation was examined on the cellular and molecular level. Plasmids for the expression of wild-type (WT) and mutated SERPINC1 coding sequence (CDS) fused to green fluorescent protein (GFP) or hemagglutinin (HA) tag were transfected into HEK293T cells. Subcellular localization and secretion of the respective fusion proteins were analyzed by confocal laser scanning microscopy and Western blot. The c.1247dupC mutation results in a frameshift in the CDS of the SERPINC1 gene and a subsequently altered amino acid sequence (p.Ser417LysfsTer48). This alteration affects the C-terminus of the AT antigen and results in impaired secretion as confirmed by GFP- and HA-tagged mutant AT analyzed in HEK293T cells. The p.Ser417LysfsTer48 mutation leads to impaired secretion, thus resulting in a quantitative AT deficiency. This is in line with the type I AT deficiency observed in the patients.

中文翻译：

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SERPINC1 c.1247dupC：与家族性血栓形成相关的新型 SERPINC1 基因突变导致分泌缺陷和定量抗凝血酶缺乏

抗凝血酶（AT）是止血中重要的抗凝剂。我们在此描述了与临床相关血栓形成相关的新型 AT 突变的特征。一对确诊为 I 型 AT 蛋白缺陷的姐妹因怀疑存在遗传性 SERPINC1 突变而接受了基因分析。鉴定出移码突变 c.1247dupC，并在细胞和分子水平上检查了该突变的影响。将表达与绿色荧光蛋白 (GFP) 或血凝素 (HA) 标签融合的野生型 (WT) 和突变型 SERPINC1 编码序列 (CDS) 的质粒转染至 HEK293T 细胞中。通过共焦激光扫描显微镜和蛋白质印迹分析各自融合蛋白的亚细胞定位和分泌。 c.1247dupC 突变导致 SERPINC1 基因 CDS 发生移码，并随后改变氨基酸序列 (p.Ser417LysfsTer48)。这种改变影响 AT 抗原的 C 末端，并导致分泌受损，这一点通过在 HEK293T 细胞中分析的 GFP 和 HA 标记的突变 AT 得到证实。 p.Ser417LysfsTer48 突变导致分泌受损，从而导致 AT 定量缺乏。这与在患者中观察到的 I 型 AT 缺陷相符。