苯丙氨酸羟化酶缺乏症基因型与表型的关系

目的研究江苏地区苯丙氨酸羟化酶缺乏症(PAHD)患儿的基因突变特点,构建本地区苯丙氨酸羟化酶(PAH)基因突变谱,讨论PAHD基因型与表型的关系。方法应用基因测序技术对70例PAHD患儿及其父母进行PAH基因第1~13外显子及两侧内含子序列分析。结果 70例患儿的140个等位基因中125个检测出突变,检出率为89.29%,常见突变依次为EX6-96AG(19/125,15.20%),R243Q(18/125,14.40%)和R241C(17/125,13.60%)。经典型苯丙酮尿症(PKU)患儿最常见突变为R243Q和EX6-96AG,共占42.86%中度PKU患儿最常见突变为EX6-96AG,R241C和R111X,共占40.74%;轻度PKU患儿最常见的突变是R241C,EX6-96AG和R243Q,共占57.89%;轻度HPA患儿最常见的突变是R241C和R243Q,共占40.00%。通过基因型预测的生化表型与患儿实际生化表型一致率为65.63%,其中经典型PKU的预测一致率较高,为81.25%;预测生化表型(即AV值评分)与患儿治疗前血苯丙氨酸水平呈显著负相关(r=-0.77,P0.001)。结论江苏地区PAH基因突变谱与其他地区有所不同,基因型与表型之间存在一定的联系。     

苯丙酮尿症患儿苯丙氨酸羟化酶基因突变的研究

目的了解宁夏地区苯丙酮尿症(PKU)儿童苯丙氨酸羟化酶(PAH)基因突变的特征。方法以经新生儿疾病筛查及气相色谱-质谱联用技术确诊的30例宁夏PKU儿童为病例组,30例正常儿童为对照组,应用PCR技术扩增PAH基因的3、5、6、7、11和12,六个外显子,再经单链构象多态性分析和DNA测序分析PCR扩增产物。结果在60个等位基因中检出51个突变基因,检出率85%;六个外显子共检出16种致病突变,包括8种错义突变(R241C、R243Q、R252Q、G 257 V、R359K*、R408Q、R 413 P、Q419R),3种剪接突变(IVS 4-1 GA、Y 204 C、IVS 7+2 TA),3种无义突变(R 111 X、Q160X、Y356X),1种同义突变(V399V)和1种缺失突变(N183del);R243Q突变频率最高,检出率为18.3%,其次是Y 204 C(11.7%)、IVS 4-1 GA(10.0%)、R 111 X(6.7%)和IVS 7+2 TA(6.7%)。病例组中发现Exon 6的N183del(C.547-549del GAA)缺失突变和Exon 11的R359K(C.1078GA)错义突变,为国内首次发现;病例组和对照组中均检出V245V(C.735GA)和Q232Q(C.696AG)两种静止突变,且差异无统计学意义(P0.05)。结论宁夏PKU儿童PAH基因六个外显子最常见的突变类型是错义突变,特别是R243Q;发现中国人群PAH基因的2种新的突变。     

宁夏苯丙酮尿症患儿苯丙氨酸羟化酶基因外显子7突变分析

目的 探讨宁夏地区苯丙酮尿症（PKU）患儿苯丙氨酸羟化酶（PAH）基因外显子7 突变类型及频率,为该地区PKU 的基因诊断和产前诊断提供依据。方法 应用PCR 产物直接测序方法,对宁夏73 例经典型PKU 患儿（回族39 例,汉族34 例）的146 个PAH 等位基因外显子7 及其旁侧内含子区域进行序列分析。结果 共检测出6 种突变基因型,分别是R243Q（14.4%）、R241C（6.8%）、IVS7+2T → A（2.7%）、L255S（0.7%）、G247V（0.7%）和G247R（0.7%）。外显子7 突变基因总频率为26.0%（38/146）,包括错义突变和剪接位点突变两种。回族患儿R241C 等位基因突变检出率高于汉族（10% vs 3%,P<0.05）。结论 宁夏地区PKU 患儿PAH 基因外显子7 突变频率最高的是R243Q,其次为R241C;回族和汉族PKU 患儿R241C 等位基因突变率不同。     

四氢生物蝶呤反应性苯丙氨酸羟化酶缺乏症的临床与基因研究

目的 探讨四氢生物蝶呤（tetrahydrobiopterin,BH4）反应性苯丙氨酸羟化酶（phenylalanine hydroxylase,PAH）缺乏症临床表型和基因型的关系。方法 38例高苯丙氨酸血症（hyperphenylalaninemia,HPA）患儿均进行口服BH。负荷试验（20ms／kg）或Phe-BH。联合负荷试验,同时进行尿蝶呤谱分析、红细胞二氢蝶啶还原酶（dihyaropteridine reductase,DHPR）测定。对7例BH4反应性PAH缺乏症患儿采用聚合酶链反应（PCR）和单链构象多态性（single strand conformation polymorphism,SSCP）分析对PAH外显子进行突变筛检,并结合DNA直接测序方法进行突变分析。结果 确诊10例BH4反应性PAH缺乏症患儿,男6例,女4例;平均年龄7．8个月;生化代谢表型均为轻度或中度HPA。7例BH4反应性PAH缺乏症患儿PAH基因型分别为S70del／-、R241C／R243Q、S70del／A389G、Y166X／-、R11lX/-、EX6-96A〉G／R241C和IVS4-1G〉A／R241C。A389G是新发现的突变基因型。结论 BH4反应性PAH缺乏症多表现为轻、中度HPA生化代谢表型,R241C是BH4反应性相关突变基因型中较常见的一种类型。推测S70del可能是一种BH4反应性相关突变类型.     

苯丙酮尿症患者32例家系基因突变研究北大核心CSCD

目的：检测苯丙酮尿症（PKU）患儿及其父母苯丙氨酸羟化酶（PAH）基因突变谱,并探讨 PAH 基因突变与临床严重程度的相关性,为本地区 PKU 患儿的早期诊断及遗传咨询提供基础数据。方法使用高通量测序技术对来自江苏省无锡和宿迁的32例 PKU 患儿及其父母的 PAH 基因13个外显子及其附近内含子区域进行测序分析。结果32例 PKU 共检测出61个突变位点,33种突变基因,突变检出率为95.31％（61/64个）。本地区 PKU 患儿常见致病突变位点为 c.721C ﹥ T、c.1068C ﹥ A、c.611A ﹥ G、c.1197A ﹥ T、c.728G ﹥ A、c.331C ﹥ T 和 c.442-1G ﹥ A,其突变频率均在5％以上。首次报道1个新的突变基因位点 c.699C ﹥ G 和3个汉族人口中新的突变基因位点 c.265C ﹥ T、c.722G ﹥ A 和 c.1194A ﹥ G。Guldberg AV 系统分析显示38.0％（8/21例）的 PKU 患者基因型与实际生化表型相一致,其中预测表型为中重度的与实际生化表型的一致率为92.3％（12/13例）,轻度的与实际生化表型的一致率为50.0％（4/8例）。结论江苏地区 PKU 患儿的 PAH 基因突变集中在外显子7上,其中频率最高的基因位点是 c.721C ﹥ T,并首次发现1个新的基因突变位点 c.699C ﹥ G;PKU 患者基因型与生化表型之间有一定的相关性。     

青海地区苯丙酮尿症患者苯丙氨酸羟化酶基因突变分析

目的 明确青海地区苯丙酮尿症患者苯丙氨酸羟化酶(PAH)基因的突变特征,为该地区苯丙酮尿症(PKU)的产前诊断和遗传咨询提供理论依据。方法 选取2006年1月至2012年12月经新生儿疾病筛查及门诊遗传咨询发现并确诊的49例青海地区PKU患儿为研究对象,应用PCR产物直接测序法对49例PKU患儿及其父母的PAH基因启动子、第1~13外显子及其旁侧内含子区域进行基因突变分析。结果 在98个PAH等位基因中检测出30种、共计80个不同的突变基因,总检出率为82%(80/98),主要包括19种错义突变(63%)、5种无义突变(17%)、3种剪切位点突变(10%)和3种缺失突变(10%),大部分突变集中在第3、6、7、11外显子及第4内含子区域,常见的4种突变是p.R243Q(19%)、IVS4-1G>A(9%)、p.Y356X(7%)和p.EX6-96A>G(5%);p.N93fsX5(c.279-282delCATC)、p.G171E(c.512G>A)突变是国际上未见报道的新的PAH基因突变,p.H64fsX9(c.190delC)突变为国内第2次报道。青海地区PAH基因的突变构成有一部分与北方各省份相似,与中国南方部分省区及日本、欧洲等国家差异显著。结论 青海地区表现出多民族聚居地区PAH基因突变特有的多样性和复杂性。     

宁夏地区苯丙酮尿症患儿苯丙氨酸羟化酶基因外显子6突变研究

目的 探讨宁夏地区苯丙酮尿症(PKU)患儿苯丙氨酸羟化酶(PAH)基因外显子6突变类型及频率,为该地区PKU的基因诊断和产前诊断提供依据.方法 应用聚合酶联反应(PCR)产物直接测序方法,对宁夏73例经典型PKU患儿[PKU患儿均为宁夏新生儿疾病筛查中心2010年1月至2013年6月确诊,病例分布于宁夏22县(市、区);年龄15 d～13岁;男38例,女35例;回族39例,汉族34例]和100例(回族50例,汉族50例)健康新生儿的PAH基因外显子6及其旁侧内含子区域进行序列分析.结果 共检测出6种基因突变型别,分别是EX6-96A＞ G(6.85％)、Q232X(2.74％)、D222G(1.37％)、V2301(1.37％)、R176X(0.68％)和N223I(0.68％),基因外显子6突变检出率为13.70％,包括3种突变型别,分别是错义突变3种(50.0％)、无义突变2种(33.3％)和剪切位点突变1种(16.7％);查阅国内外文献,其中EX6-96A＞G、Q232X和R176X国内早有报道,D222G、V2301为国内首次报道的PAH突变,N223I为国际上尚未见报道的新PAH突变.结论 明确了宁夏地区PAH基因外显子6突变类型及频率,丰富了该地区PKU基因研究,为开展PKU的基因诊断提供依据.     

苯酮尿症的分子研究及其基因型-表型相关性的研究进展

苯酮尿症(phenlketonuria,PKU)主要是由于编码苯丙氨酸羟化酶(PAH)的基因突变,导致肝脏PAH活性降低或缺乏所致。各国应用分子生物学等技术对PAH基因突变进行了广泛研究,到目前为止,有498突变基因被确定,其中致病性的突变有460余种;研究者们应用体外表达预测酶活性和测定体内苯丙氨酸氧化率等方法研究基因型-表型的相关性,希望通过基因型来预测未知的表型,以便指导PKU的分类和治疗。该文综述了PAH基因突变在不同地区、人种和民族的特点,同时对基因型-生化代谢表型以及基因型-智能表型的相关关系的研究进行综合分析。     

携带 I2G 突变的 21 羟化酶缺乏症患儿基因突变谱与 临床表型的关系

目的探讨携带I2G基因突变的21羟化酶缺乏症(21-OHD)患儿基因突变谱,分析基因型与临床表型的关系。方法收集2009-2016年间收治的携带I2G基因突变的21-OHD患儿的临床资料,分析基因型与临床表型的关系。结果共26例患儿,男20例、女5例,失盐型(SW)22例(84.62%),单纯男性化型(SV)4例(15.38%)。I2G纯合突变16例(61.5%),除1例男童临床表现为SV外,其余15例均表现为SW。复合杂合突变10例(38.5%),其中7例为SW,分别携带有p.Q319X、p.R357W、p.R484P、p.V282L、Gll0fs、Cluster E6基因突变;1例SV女童携带p.I172N突变基因,另外2例SV男童(同胞兄弟)均携带p.Q319X突变及父源等位基因大片段重复,而母源等位基因上存在I2G杂合突变。结论携带I2G基因突变的21-OHD患儿基因型与临床表型有较好的一致性,纯合突变多表现为SW,复合杂合突变的临床表现主要取决于酶活性损害较轻的突变基因。     

新疆维吾尔族儿童21-羟化酶缺乏症基因型与表型的研究

目的 探讨新疆维吾尔族儿童21-羟化酶缺乏症(21-OHD)基因突变规律及基因型和临床表型的关系。方法 选取2013年10月至2014年10月就诊的20例维吾尔族21-OHD患儿为研究对象,联合应用全长直接测序法和多重连接依赖探针扩增技术检测21-羟化酶编码基因CYP21A2的突变类型,并按照基因突变类型将21-OHD患者分成不同的组别,比较预期的临床表型和实际临床表型的一致性。结果 20例患儿共发现9种突变,其中8种为已确定的致病突变,分别为Del、conv、I2g、I172N、Cluster E6、8-bp del、V281L、R356W,另1种突变为内含子5上的新发突变(c.648+37A>G),目前尚未有相关文献报道,暂不明确是否具有病理性意义。大部分根据基因突变类型预测的临床表型与实际的临床表型符合率较高(67%以上),根据P30L、V281L突变预测的临床表型与实际临床表型符合率较低(33%)。结论 21-OHD的基因型与表型有较好的相关性,通过检测患者的基因型可以预测疾病的临床表型;新发突变(c.648+37A>G)可能与21-OHD的发病有一定的关系。     

Molecular analysis of PKU in Ireland

Classical phenylketonuria (PKU: McKusick No. 261600) is caused by mutations occurring at the phenylalanine hydroxylase (PAH) locus on chromosome 12 and has a prevalence in Ireland of 1 in 4500. We examined 304 independent alleles from 350 patients for the presence of six mutations and have characterized VNTR alleles within the minisatellite region 3' to the PAH gene in patients carrying the most prevalent mutation. R408W was the most common mutation found, with a relative frequency of 42%. All other mutations had relative frequencies of <10%. VNTR analysis showed that the R408W mutation is associated with the VNTR-8 allele in the Irish population, indicating that R408W is associated with RFLP haplotype 1. This differs from that reported from eastern Europe where R408W is associated with RFLP haplotype 2/VNTR-3; an observation which has led several groups to propose a Balto-Slavic origin for this mutation. These results support the hypothesis of a second, independent founding event for the R408W mutation on an RFLP haplotype 1 VNTR-8 chromsome background in the Irish/Celtic population.     

Mutations in the phenylalanine hydroxylase gene: genetic determinants for the phenotypic variability of hyperphenylalaninemia

Phenylalanine hydroxylase (PAH) deficiency is heterogeneous disease at the phenotype level. The spectrum of clinical and metabolic phenotypes spans from the potential pathogenic disease classical phenylketonuria (PKU) to the benign condition non-PKU hyperphenylalaninemia (non-PKU HPA). This review provides an introduction to the clinical variants of PAH deficiency, and summarizes our attempts to define the disease at the molecular level and to relate mutation genotype to clinical outcome. Complete genotype determination in a large number of patients with PAH-deficient hyperphenylalaninemia demonstrates that clinical heterogeneity can be explained by a multiplicity of mutations in the PAH gene. Some combinations of mutations are associated with phenylalanine levels fluctuating around the border between PKU and non-PKU HPA. However, certain mutations seem always to cause non-PKU HPA irrespective of the mutation on the second allele and can, therefore, unambiguously be designated as being associated with the non-PKU HPA phenotype. Our results suggest that mutation analysis in newborns presenting with hyperphenylalaninemia can be used for rapid and highly efficient differential diagnosis of PAH deficiency, and for predicting the severity of the disease. These possibilities may facilitate and optimize the management of hyperphenylalaninemia and thereby improve prognosis.     

Genetic background of hyperphenylalaninemia in Nagasaki,Japan

Phenylketonuria (PKU) and related hyperphenylalaninemia (HPA) are caused by a deficiency in hepatic phenylalanine hydroxylase (PAH). The incidence of PKU in Nagasaki prefecture is higher than that in all parts of Japan (1/15 894 vs 1/120 000). To investigate the genetic background of patients with HPA in Nagasaki prefecture, mutation analysis was done in 14 patients with PKU or mild HPA. Homozygous or compound heterozygous PAH mutations were identified in all the patients. The spectrum of PAH mutations in the cohort was broad and similar to those in all parts of Japan and East Asian countries. R53H is the most common mutation in patients with mild HPA. The present results provide further support for genotype–phenotype correlations in patients with HPA. The high incidence of PKU in Nagasaki, the westernmost part of Japan, might be due to migration of people with PAH mutations from China and Korea, and geographic factors.     

Long-term treatment and diagnosis of tetrahydrobiopterin-responsive hyperphenylalaninemia with a mutant phenylalanine hydroxylase gene

A novel therapeutic strategy for phenylketonuria (PKU) has been initiated in Japan. A total of 12 patients who met the criteria for tetrahydrobiopterin (BH(4))-responsive hyperphenylalaninemia (HPA) with a mutant phenylalanine hydroxylase (PAH) (EC 1.14.16.1) gene were recruited at 12 medical centers in Japan between June 1995 and July 2001. Therapeutic efficacy of BH(4) was evaluated in single-dose, four-dose, and 1-wk BH(4) loading tests followed by long-term BH(4) treatment, and also examined in relation to the PAH gene mutations. The endpoints were determined as the percentage decline in serum phenylalanine from initial values after single-dose (>20%), four-dose (>30%), and 1-wk BH(4) (>50%) loading tests. Patients with mild PKU exhibiting decreases in blood phenylalanine concentrations of >20% in the single-dose test also demonstrated decreases of >30% in the four-dose test. The 1-wk test elicited BH(4) responsiveness even in patients with poor responses in the shorter tests. Patients with mild HPA, many of whom carry the R241C allele, responded to BH(4) administration. No clear correlation was noted between the degree of decrease in serum phenylalanine concentrations in the single- or four-dose tests and specific PAH mutations. The 1-wk test (20 mg/kg of BH(4) per day) is the most sensitive test for the diagnosis of BH(4)-responsive PAH deficiency. Responsiveness apparently depends on mutations in the PAH gene causing mild PKU, such as R241C. BH(4) proved to be an effective therapy that may be able to replace or liberalize the phenylalanine-restricted diets for a considerable number of patients with mild PKU.     

青岛市苯丙氨酸羟化酶缺乏症患儿基因突变分析

目的探讨青岛市苯丙氨酸羟化酶(phenylalanine hydroxylase,PAH)缺乏症患儿的基因突变特点,为青岛市PAH缺乏症的产前诊断、治疗提供科学参考依据。方法对经青岛市新生儿疾病筛查确诊的44例PAH缺乏症患儿,应用第二代高通量测序及多重连接酶探针依赖扩增(multi-ligase probe dependent amplification,MLPA)技术进行基因分析,检测患儿基因突变位点,应用Sanger测序对其父母的PAH基因相应突变位点进行检测并验证。根据患儿血苯丙氨酸浓度,分为经典型苯丙酮尿症、轻度苯丙酮尿症和轻度高苯丙氨酸血症。结果①44例PAH缺乏症患儿PAH基因中均检测到2个突变位点,其中2例为纯合突变,纯合突变的频率为4.6%,所有突变在患儿父母相应突变位点处均能检测到。②44例PAH缺乏症患儿共检测到突变36种,其中c.728G>A突变频率最高(15.9%,14/88),其次是c.1068C>A(10.2%,9/88),再次为c.158G>A(9.1%,8/88)。③21例经典型苯丙酮尿症患儿PAH基因突变19种,其中c.1068C>A突变频率最高(21.4%,9/42),其次是c.728G>A(19.0%,8/42)。10例轻度苯丙酮尿症患儿PAH基因突变14种,其中c.721C>T/722delG突变频率最高(15.0%,3/20),其次为c.1197A>T、c.1301C>A、c.721C>T、c.728G>A(均为10.0%,2/20)。13例轻度高苯丙氨酸血症患儿PAH基因突变17种,其中c.158G>A突变频率最高(26.9%,7/26),其次为c.728G>A(15.4%,4/26)。结论青岛市PAH缺乏症患儿PAH基因突变以复合杂合突变为主,具有明显热点突变(c.728G>A、c.1068C>A、c.158G>A),经典型苯丙酮尿症患儿以c.1068C>A、c.728G>A为主,轻度苯丙酮尿症患儿以c.721C>T/722delG为主,轻度高苯丙氨酸血症患儿以c.158G>A为主。本研究明确了青岛市PAH缺乏症患儿基因的突变类型与特点,为深入开展PAH缺乏症的诊断以及进一步的基因治疗奠定了基础。     

Relation between genotype and phenotype in Swedish phenylketonuria and hyperphenylalaninemia patients

Phenylketonuria (PKU) and hyperphenylalaninemia (HPA) are caused mostly by an inherited (autosomal recessive) deficiency in hepatic phenylalanine hydroxylase (PAH) activity. More than 50 PAH mutations have ben reported. The goal of the present study was to examine the molecular basis for the clinical heterogeneity of Swedish PKU and HPA patients. Mutations were identified through allele-specific oligonucleotide hybridization or DNA sequencing on 128 of the 176 mutant alleles (73%). Three mutations (R408W, Y414C and IVS12) together accounted for 56% of all mutant alleles and ten relatively infrequent mutations were found on another 17% of all mutant alleles. Patients from 50 of the 88 families (57%) had identified mutations in both PAH genes and allowed use to compare the clinical effects of different combinations of PAH mutations. The in vitro activity of all of these mutations, including the newly identified G272X and L364, have been tested in a eukaryotic expression system. There was a strong relationship between the average in vitro PAH activity of the two mutant enzymes and both the phenylalanine tolerance and the neonatal pretreatment serum phenylalanine concentration. This confirms previous observations in Danish and German PKU patients that disease phenotype is a consequence of the nature of the mutations at the PAH locus and not significantly influenced by other loci. The sample population in the previous study did not, however, include mild HPA patients, and the observed correlation is thus restricted to severe and moderate mutant alleles. Since a comparatively high proportion of the Swedish patients were mildly affected, we have provided additional evidence that this correlation is valid throughout a continuous spectrum of clinical varieties. PAH genotyping could therefore help predict prognosis of a recently diagnosed PKU or HPA child.     

Population genetics of phenylketonuria

Phenylketonuria (PKU) is an autosomal recessive disorder caused by a large number of mutations at the phenylalanine hydroxylase (PAH) locus, most of which are strongly associated with specific RFLP or VNTR haplotypes. One of the major questions remaining in PKU research is why this apparently maladaptive disorder has been maintained at a frequency of approximately 1 in 10000 among Caucasians. A growing number of studies have provided evidence that both the relatively high frequency of PKU and the strong mutation/haplotype associations might reflect the existence of multiple founding populations for PKU. Examples of putative founding populations for PKU in both Europe and Asia will be presented. Some PAH mutations are associated with multiple haplotypes, suggesting recurrence. Evidence for and against recurrence as the mechanism responsible for the association of the R408W mutation with RFLP haplotypes 1 and 2 will be discussed.