DNA Diagnosis of Non-ketotic Hyperglycinemia

非酮症性高血糖(NKH)是一种公认的新生儿生命危险疾病的代谢原因。最基本的缺陷是甘氨酸裂解系统(GCS)，它由四个蛋白质组分组成。我们的研究显示，大多数NKH患者在P蛋白(甘氨酸脱羧酶)方面存在特定的缺陷。GCS在肝脏、肾脏和脑中特异表达。因此，肝活检对于NKH的酶学诊断是必要的。本研究旨在建立NKH的DNA诊断方法。对NKH患者的P-蛋白mRNA进行结构分析，发现其存在点突变、三个碱基缺失或一个碱基缺失等分子损伤，导致框架移位。总之，S564I突变(Ser^lt；564&gt；到Ile^&lt；564&gt；)是芬兰NKH患者的常见突变。每个正向和反向引物中的一个核苷酸被修饰，以产生限制性内切酶Rsa I和Ssp I的识别位点。利用该方法，可以方便地利用滤纸上的干血诊断S564I突变的纯合子和杂合子。用该方法对妊娠8~16周的绒毛进行产前诊断也是可行的。

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.