Division of Laboratory Medicine, Chiba University Hospital, Chiba, Japan.
Division of Clinical Genetics, Chiba University Hospital, Chiba, Japan.
J Med Genet. 2018 Oct;55(10):701-704. doi: 10.1136/jmedgenet-2017-104964. Epub 2018 Jan 13.
A genetic diagnosis has been rarely performed in benign familial hyperphosphatasaemia, and molecular mechanism largely remains unclear.
We encountered a case with benign familial hyperphosphatasaemia of intestinal alkaline phosphatase (IAP). To elucidate the molecular mechanism, we performed gene sequencing and in vitro protein expression analysis.
gene was sequenced by long-range PCR and massively parallel sequencing. The soluble and membrane-bound ALP activities of the cultured cell line, transfected with the wild-type or variant-type gene were analysed by a glycosylphosphatidylinositol (GPI)-cleaving assay.
We identified a deletion-insertion variant in the C-terminal end of the gene. This variant causes the attenuation of the hydrophobicity in GPI-anchor signal of IAP. An in vitro GPI-cleaving assay demonstrated that the membrane-bound IAP was greatly decreased, whereas the soluble IAP was increased, in the variant IAP.
The C-terminal variant in causes the benign familial hyperphosphatasaemia of IAP by the attenuation of the membrane-binding capability.
良性家族性磷酸酶过多症很少进行基因诊断，分子机制仍不清楚。
我们遇到了一例肠碱性磷酸酶（IAP）的良性家族性磷酸酶过多症。为了阐明分子机制，我们进行了基因测序和体外蛋白表达分析。
通过长距离 PCR 和大规模平行测序对基因进行测序。通过糖基磷脂酰肌醇（GPI）切割测定法分析转染野生型或变异型基因的培养细胞系的可溶性和膜结合 ALP 活性。
我们在基因的 C 末端发现了一个缺失-插入变异。该变体导致 IAP 的 GPI-锚定信号的疏水性减弱。体外 GPI 切割测定表明，变体 IAP 中的膜结合 IAP 大大减少，而可溶性 IAP 增加。
基因的 C 末端变异通过降低膜结合能力导致 IAP 的良性家族性磷酸酶过多症。
