苯丙氨酸羟化酶基因新突变位点与临床的关系

The correlation of genotypes and phenotypes for two novel mutations in phenylalanine hydroxylase gene

的观察新发现的两种苯丙氨酸羟化酶基因突变与临床表现型的关系，对其中一个位点进行基因表达的研究。方法通过变性梯度凝胶电泳（ＤＧＧＥ）突变检测和固相ＤＮＡ直接序列分析等方法，对５８例苯丙酮尿症（ＰＫＵ）患儿进行突变检测，对新突变进行体外寡核苷酸定点诱变和在ＣＯＳ细胞中ＰＡＨ活性表达研究。结果共发现有ＩＶＳ６ｎｔ１的Ｇ→Ａ突变和Ａｒｇ２５２Ｇｌｎ突变的患儿７例，均有典型的ＰＫＵ临床表现，并有不同程度的智能低下，苯丙氨酸浓度均大于１．２ｍｍｏｌ／Ｌ。带有Ａｒｇ２５２Ｇｌｎ突变位点的ｃＤＮＡ表达的ＰＡＨ酶活性为野生型的２４％。结论上述两种新发现的突变是致病性的，但相同基因型的患者临床表现并不均一；携带Ａｒｇ２５２Ｇｌｎ位点突变的患者ＰＡＨ酶活性明显降低。

Objective To determine the correlation of the genotype and the phenotype for two novel mutations in phenyla lanine hydroxylase gene, and to study the expression of one of the mutated genes. Methods The mutations were analysed using denaturing gradient gel electrophoresis, DNA direct sequencing and in vitro expression. Results Seven children with the mutations of GA in IVS6nt1 and Arg252Gln manifested clinically with the typical phenylketonuria and mental retartation. The concentration of phenylalanine in the children were all more than 1 200 mol/L. The mutation of IVS6nt1 is an intronexon junctional mutation that results in a splicing defect in mRNA. The residual PAH activity of Arg252Gln is only 24% of the wild type in mutagenesis in vitro and expressions in COS cells. Conclusion The patients carrying these two mutations demonstrated a strong correlation between genotypes and phenotypes, but clinical manifestations were not homogenous for the same mutation.