DNA Diagnosis of Non-ketotic Hyperglycinemia

非酮性高甘氨酸血症（NKH）是公认的新生儿危及生命的疾病的代谢原因。其根本缺陷在于甘氨酸裂解系统（GCS），该系统由四种蛋白质组分组成。我们的研究表明，大多数NKH患者有一个特定的缺陷P蛋白（甘氨酸脱羧酶）。GCS在肝、肾和脑中特异性表达。本研究对NKH患者的P蛋白mRNA进行结构分析，发现NKH患者的P蛋白mRNA存在点突变、三碱基缺失或一碱基缺失导致的移码等分子损伤。总之，S564 I突变（一种由Ser^→ Ile^的氨基酸改变<564><564>）是芬兰NKH患者中常见的突变，我们建立了一种快速简便的检测S564 I突变的改良PCR方法。在每个正向和反向引物中的一个核苷酸被修饰以在PCR产物中产生限制性酶Rsa I和Ssp I的识别位点。该方法可利用滤纸干血方便地诊断S564I突变的纯合子和杂合子。产前诊断也是可行的，通过这种方法使用绒毛膜绒毛之间获得的第8和第16周的妊娠。

Nonketotic hyperglycinemia (NKH) is a well-recognized metabolic cause of life-threatening illness in the neonate. The foundamental defect is in the glycine cleavage system (GCS), which consists of four protein components. Our study revealed that the majority of NKH patients had a specific defect in P-protein (glycine decarboxylase). GCS is specially expressed in liver, kidney and brain. Liver biopsy is, therefore, necessary for the enzymatic diagnosis of NKH.This study was carried out to establish DNA diagnosis of NKH.structual analyzes of P-protein mRNA from the patients with NKH revealed molecular lesions such as point mutations, three-base deletion or one-base deletion resulting in frame shift. Above all, S564I mutation (an amino acid alternation from Ser^<564> to Ile^<564>) was found to be a common mutation in Finnish patients with NKH.We developed a modified PCR method to detect S564I mutation rapidly and easily. One nucleotide in each forward and reverse primer was modified to produce recognition sites for restriction enzymes, Rsa I and Ssp I in the PCR products. With this method, we could diagnosis homozygotes and heterozygotes of S564I mutation easily using dried blood on filter paper. Prenatal diagnosis also was feasible by this method using choriomic villi obtained between 8th and 16th weeks of gestation.