Conter C, Rolland M O, Cheillan D, Bonnet V, Maire I, Froissart R
Centre d'Etude des Maladies Métaboliques, Hôpital Debrousse, Lyon, France.
J Inherit Metab Dis. 2006 Feb;29(1):135-42. doi: 10.1007/s10545-006-0202-6.
Glycine encephalopathy, or nonketotic hyperglycinaemia (NKH; Mckusick 238300) is a severe autosomal recessive disease due to a defect in the glycine cleavage system (GCS), which is a complex of four subunits: P-, T-, H- and L-proteins. A P-protein (glycine decarboxylase or GLDC) deficiency was reported in about 80% of NKH patients. We performed mutation analysis of the complete coding sequence of the GLDC gene in 28 unrelated patients with neonatal NKH using denaturing high-performance liquid chromatography (DHPLC) and sequencing. Forty different gene alterations were identified, confirming the large molecular heterogeneity of the GLDC gene. Eighteen alterations were clearly disease-causing: two large deletions, four one-base deletions (c.28delC, c.1175delC, c.2186delC, c.2422delA), one 1-base insertion (c.1002_1003insT), one 4-base insertion (c.1285_1286insCAAA), one insertion/deletion (c.2153_2155delinsTCCTGGTTTA), five nonsense mutations (p.E153X, p.R236X, p.E270X, p.R337X, p.R424X) and four splice site mutations (c.861+1G > T, c.1402-1C > G, c.2316-1G > A, c.2919+1G > A). Additionally, we identified one intronic mutation outside the consensus splice sites (c.2838+5G > A) and 21 nucleotide substitutions leading to amino acid change (including three previously described mutations: p.T269M, p.R461Q, p.G771R), the pathogenicity of which should be confirmed by expression studies (p.S132W, p.Y138F, p.G171A, p.T187K, p.R212K, p.T269M, p.R373W, p.I440N, p.R461Q, p.N533Y, p.C644F, p.H651R, p.V705M, p.N732K, p.G771R, p.H775R, p.T830M, p.A841P, p.D880V, p.S957P and p.R966G). Mutation analysis allowed us to identify sequence alterations in both alleles for 19 patients and in one allele for 7 patients One patient was carrying three mutations (p.Y138F, p.T269M and p.E153X) and one patient was carrying two amino acid substitutions on the same allele (p.V705M and p.R212K) and an unidentified mutation on the other allele. No mutation could be found in two patients, suggesting possible defects in the H-protein or gene alterations that could not be identified by our technique. The potential use of genotype determination for prenatal diagnosis is emphasized.
甘氨酸脑病，即非酮症高甘氨酸血症（NKH；麦库西克编号238300），是一种严重的常染色体隐性疾病，由甘氨酸裂解系统（GCS）缺陷所致，该系统由四个亚基组成：P蛋白、T蛋白、H蛋白和L蛋白。约80%的NKH患者存在P蛋白（甘氨酸脱羧酶或GLDC）缺陷。我们使用变性高效液相色谱（DHPLC）和测序技术，对28例无关的新生儿NKH患者的GLDC基因完整编码序列进行了突变分析。共鉴定出40种不同的基因改变，证实了GLDC基因存在较大的分子异质性。其中18种改变明显致病：2种大片段缺失、4种单碱基缺失（c.28delC、c.1175delC、c.2186delC、c.2422delA）、1种单碱基插入（c.1002_1003insT）、1种4碱基插入（c.1285_1286insCAAA）。1种插入/缺失（c.2153_2155delinsTCCTGGTTTA）、5种无义突变（p.E153X、p.R236X、p.E270X、p.R337X、p.R424X）和4种剪接位点突变（c.861+1G>T、c.1402-1C>G、c.2316-1G>A、c.2919+1G>A）。此外，我们还鉴定出1种位于共有剪接位点之外的内含子突变（c.2838+5G>A）以及21种导致氨基酸改变的核苷酸替换（包括3种先前描述的突变：p.T269M、p.R461Q、p.G771R），其致病性需通过表达研究来证实（p.S132W、p.Y138F、p.G171A、p.T187K、p.R212K、p.T269M、p.R373W、p.I440N、p.R461Q、p.N533Y、p.C644F、p.H651R、p.V705M、p.N732K、p.G771R、p.H775R、p.T830M、p.A841P、p.D880V、p.S957P和p.R966G）。突变分析使我们能够确定19例患者两个等位基因的序列改变以及7例患者一个等位基因的序列改变。1例患者携带3种突变（p.Y138F、p.T269M和p.E153X），1例患者在同一等位基因上携带2种氨基酸替换（p.V705M和p.R212K），另一个等位基因存在未鉴定的突变。2例患者未发现突变，提示可能存在H蛋白缺陷或我们的技术无法鉴定的基因改变。文中强调了基因型测定在产前诊断中的潜在用途。
