Exome sequencing reveals a thrombopoietin ligand mutation in a Micronesian family with autosomal recessive aplastic anemia
Exome sequencing reveals a thrombopoietin ligand mutation in a Micronesian family with autosomal recessive aplastic anemia
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DOI：
10.1182/blood-2012-12-473538
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发表时间：
2013-11-14
期刊：
影响因子：
20.3
通讯作者：
Saadi, Irfan
中科院分区：
文献类型：
--
作者：
Dasouki, Majed J.;Rafi, Syed K.;Saadi, Irfan
我们最近发现两个兄弟姐妹患有特发性常染色体隐性遗传性再生障碍性贫血。全外显子测序在两个受影响的兄弟姐妹中发现了一种新的血小板生成素纯合子错义突变(THPO，c.112C>；T)。该突变编码精氨酸取代半胱氨酸，在第38位或第17位，不包括THPO受体结合区(RBD)的21个氨基酸的信号肽。THPO在其RBD中有4个保守的半胱氨酸，形成2个二硫键。我们的电子模型预测，引入第五个半胱氨酸可能会扰乱正常的二硫键结合，导致受体结合不良。在功能分析中，含有突变THPO的培养液显示出支持UT7-TPO细胞的能力降低了两到三倍，而UT7-TPO细胞需要THPO才能增殖。具有R17C杂合子变化的父母和兄弟姐妹都降低了血小板计数，而具有野生型序列的兄弟姐妹的血小板计数正常。因此，在我们家系中，R17C部分功能缺失等位基因导致纯合子状态的再生障碍性贫血和杂合子状态的轻度血小板减少。结合最近发现的THPO受体(MPL)突变和THPO激动剂在再生障碍性贫血中的作用，我们的结果对再生障碍性贫血患者的诊断和治疗具有临床意义，并强调了THPO-MPL途径在体内造血中的作用。
We recently identified 2 siblings afflicted with idiopathic, autosomal recessive aplastic anemia. Whole-exome sequencing identified a novel homozygous missense mutation in thrombopoietin (THPO, c. 112C>T) in both affected siblings. This mutation encodes an arginine to cysteine substitution at residue 38 or residue 17 excluding the 21-amino acid signal peptide of THPO receptor binding domain (RBD). THPO has 4 conserved cysteines in its RBD that form 2 disulfide bonds. Our in silico modeling predicts that introduction of a fifth cysteine may disrupt normal disulfide bonding to cause poor receptor binding. In functional assays, the mutant-THPO-containing media shows two-to threefold reduced ability to sustain UT7-TPO cells, which require THPO for proliferation. Both parents and a sibling with heterozygous R17C change have reduced platelet counts, whereas a sibling with wild-type sequence has normal platelet count. Thus, the R17C partial loss-of-function allele results in aplastic anemia in the homozygous state and mild thrombocytopenia in the heterozygous state in our family. Together with the recent identification of THPO receptor (MPL) mutations and the effects of THPO agonists in aplastic anemia, our results have clinical implications in the diagnosis and treatment of patients with aplastic anemia and highlight a role for the THPO-MPL pathway in hematopoiesis in vivo.