Fatal Hepatic Short-Chain L-3-Hydroxyacyl-Coenzyme A Dehydrogenase Deficiency: Clinical, Biochemical, and Pathological Studies on Three Subjects with This Recently Identified Disorder of Mitochondrial β-Oxidation

This report describes the clinical, biochemical, and pathological findings in three infants with hepatic short-chain L-3-hydroxyacyl-coenzyme A dehydrogenase (SCHAD) deficiency, a recently recognized disorder of the mitochondrial oxidation of straight-chain fatty acids. Candidate subjects were identified from an ongoing study of infant deaths. SCHAD analysis was performed on previously frozen liver and skeletal muscle on subjects with a characteristic urine organic acid profile. Autopsy findings were correlated with the biochemical abnormalities. Enzyme analysis in liver revealed marked deficiency in SCHAD with residual activities of 3–11%. All subjects had normal activity in skeletal muscle. However, Western blot analysis of SCHAD revealed an identical truncated protein in both liver and muscle from one patient, suggesting that SCHAD is similar in liver and muscle and that the normal activity in muscle may be due to other enzymes with C4 activity. Autopsy findings revealed marked steatosis and a muscle pattern consistent with spinal muscular atrophy in one patient. Lipid storage was less pronounced in one patient and not detected in the third patient who had a well-documented history of recurrent hypoglycemia. This is the initial pathological characterization of this enzyme defect, and our observations suggest that SCHAD deficiency is a very severe disorder contributing to early infant death. Received March 20, 1998; accepted August 7, 1998.     

Mitochondrial fatty acid beta-oxidation in the human eye and brain: implications for the retinopathy of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

The retinal pigment epithelium (RPE) and the choriocapillaris are affected early in the retinopathy associated with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency. RPE in culture possesses the machinery needed for mitochondrial fatty acid beta-oxidation in vitro. To further elucidate pathogenesis of LCHAD retinopathy, we performed immunohistochemistry of the human eye and brain with antibodies to beta-oxidation enzymes. Human eye and brain sections were stained with antibodies to medium-chain (MCAD) and very long-chain acyl-CoA dehydrogenase (VLCAD), short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD), and mitochondrial trifunctional protein (MTP) harboring LCHAD. Antibodies to 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) and cytochrome c oxidase subunit I (COX I) were used as a reference. VLCAD, MTP, MCAD, SCHAD, MHBD, and COX I antibodies labeled most retinal layers and tissues of the human eye actively involved in oxidative metabolism (extraocular and intraocular muscle, the RPE, the corneal endothelium, and the ciliary epithelium). MTP and COX I antibodies labeled the inner segments of photoreceptors. The choriocapillaris was labeled only with SCHAD and MCAD antibodies. In the brain, the choroid plexus and nuclei of the brain stem were most intensely labeled with beta-oxidation antibodies, whereas COX I antibodies strongly labeled neurons in several regions of the brain. Mitochondrial fatty acid beta-oxidation likely plays a role in ocular energy production in vivo. The RPE rather than the choriocapillaris could be the critical affected cell layer in LCHAD retinopathy. Reduced energy generation in the choroid plexus may contribute to the cerebral edema observed in patients with beta-oxidation defects.     

Carnitine content and expression of mitochondrial beta-oxidation enzymes in placentas of wild-type (OCTN2(+/+)) and OCTN2 Null (OCTN2(-/-)) Mice

Placenta requires energy to support its rapid growth, maturation, and transport function. Fatty acids are used as energy substrates in placenta, but little is known about the role played by carnitine in this process. We have investigated the role of carnitine in the expression of the enzymes involved in fatty acid beta-oxidation in placenta of OCTN2(-/-) mice with defective carnitine transporter (OCTN2). Heterozygous (OCTN2(+/-)) female mice were mated with heterozygous (OCTN2(+/-)) male mice. Pregnant mice were killed and fetuses and placentas were collected. Carnitine was measured using HPLC and tandem mass spectrometry. Immunohistochemistry was used to detect enzyme expression. Enzyme activities were measured spectrophotometrically. The fetal and placental weights were similar among the three genotypes (OCTN2(+/+), OCTN2(+/-), and OCTN2(-/-)). The levels of carnitine were markedly reduced (<20%) in homozygous OCTN2(-/-) null fetuses and placentas compared with wild-type OCTN2(+/+) controls. However, carnitine concentration in placenta was 2- to 7-fold higher than in the fetus in all three genotypes. Immunohistochemistry revealed that beta-oxidation enzymes are expressed in trophoblast cells. Catalytic activities of these enzymes were present at comparable levels in wild-type (OCTN2(+/+)) and homozygous (OCTN2(-/-)) mouse placentas, with the exception of SCHAD, for which activity was significantly higher in OCTN2(-/-) placentas than in OCTN2(+/+) placentas. These data show that placental OCTN2 is obligatory for accumulation of carnitine in placenta and fetus, that fatty acid beta-oxidation enzymes are expressed in placenta, and that reduced carnitine levels up-regulate the expression of SCHAD in placenta.     

中国人多种羧化酶缺陷症患儿4例及其父母基因突变分析

目的研究中国人多种羧化酶缺陷症（multiple carboxylase deficiency,MCD）患儿及其父母基因突变情况。方法应用聚合酶链反应-直接测序的方法,对4例临床确诊MCD的中国患儿的生物素酶（BT）基因和全羧化酶合成酶（HLCS）基因的各个外显子及其两侧侧翼序列进行突变的检测,并对其父母进行相应突变基因检测。结果4例患儿皆为HLCS基因突变,没有发现BT基因突变。共发现1个缺失突变：780de1G,3个错义突变：1522C〉T（R508W）、1367A〉G（Y456C）和1900G〉A（I）634N）。例1为HLCS基因的第11号外显子上的1522C〉T的错义突变,为纯合突变;例2为第11号外显子的1522C〉T和第9号外显子的1367A〉G的复合性杂合突变;例3为第11号外显子的1522C〉T和第13号外显子的1900G〉A的复合性杂合突变;例4为第11号外显子的1522C〉T和第7号外显子的780de1G的复合性杂合突变;4例患儿的父母均是突变基因携带者。结论R508W突变可能是中国MCD中HLCS缺陷患儿较常见的突变。     

自身免疫性多内分泌腺病综合征Ⅰ型分子遗传学研究进展

自身免疫性多内分泌腺病综合征Ⅰ型(APS-Ⅰ)是一种罕见的常染色体隐性遗传病,致病基因为自身免疫调节因子基因.已报道的致病性突变包括无义突变、错义突变、沉默突变、插入和缺失以及剪接位点突变等,该文就APS-Ⅰ致病基因的突变特征归纳综述.     

先天性甲状腺功能减低症患儿DUOXA2基因突变研究

目的 探讨广州地区先天性甲状腺功能减低症(CH)患儿DUOXA2基因突变特点及其基因型与表型的关系。方法 采用PCR及直接测序法,对2011年至2012年出生、广州市新生儿筛查中心诊断并排除DUOX2基因突变的20例疑似甲状腺激素合成障碍的CH患者进行DUOXA2基因突变分析。结果 20例CH患者中2例为p.Y246X/p.Y246X纯合突变;4例为单等位基因杂合突变:分别为已知致病突变c.413-414ins A携带者2例,p.Y246X携带者1例,新突变p.G79R携带者1例。2~3岁再评估时显示,2例p.Y246X/p.Y246X纯合突变者分别表现为暂时性CH及轻度永久性CH;4例单等位基因突变者,除1例p.Y246X携带者表现为典型永久性CH外,其余3例携带者均为暂时性CH。结论 DUOXA2基因突变是广州地区疑似甲状腺激素合成障碍性CH患儿较常见的分子发病基础,多数表现为暂时性CH,未发现DUOXA2基因型与表型的关系。新突变p.G79R为致病性突变的可能性大。     

小儿急性淋巴细胞白血病免疫表型临床特点

急性白血病是儿科最常见的恶性肿瘤之一 ,单克隆抗体的应用为白血病的分型开辟了一条新途径 ,对指导治疗和判断预后均有重要意义 ,我们对 1 995年 2月～ 1 997年 1 2月在我院收治的 42例小儿急性淋巴细胞白血病 ( ALL)的原始细胞进行了免疫表型的分析 ,现报告如下 :材料与方法1 .病例　 42例 ALL ,男 2 7例 ,女 1 5例 ,年龄 1 12 岁～ 1 4岁 ,均为初诊病例 ,除 3例放弃治疗外 ,均接受了 1个疗程以上的化疗 ,治疗方法采用小儿急性白血病诊疗建议(修订草案 ) (1 ) 中的治疗方案。2 .方法　免疫表型的检测　取肝素抗凝的骨髓或外周血 ,桥联…     

新复合杂合突变致婴儿型低磷酸酯酶症1例及其家系分析

该文对1例婴儿型低磷酸酯酶症(HPP)患儿及其家系进行临床特点分析及碱性磷酸酯酶基因(ALPL)检测。先证者,男,5个月,多发骨骼畸形:胸骨凹陷、双侧桡骨弯曲畸形、双膝外翻畸形,伴喂养困难、体重下降、发育迟滞、反复肺炎并呼衰,血碱性磷酸酶显著降低。患儿父母、姐姐、叔父、姨母(其他家系成员未能配合)中除父母及姨母的碱性磷酸酶略低,姨母可见脊柱侧弯畸形,余均无临床表型及实验室异常。患者ALPL基因检测到来源于母亲的c.228delG突变及来源于父亲的c.407GA复合杂合突变,其姨母携带c.228delG突变。c.407GA突变为已报道的HPP致病突变,c.228delG为新的致病性突变。低磷酸酯酶症是由ALPL基因突变所致,ALPL基因检测是有效的诊断方法。该研究拓展了ALPL基因突变谱,为HPP的基因诊断提供了理论依据。     

Low TSH congenital hypothyroidism: identification of a novel mutation of the TSH beta-subunit gene in one sporadic case (C85R) and of mutation Q49stop in two siblings with congenital hypothyroidism

Isolated congenital hypothyroidism resulting from mutation of the TSH beta-subunit gene, has rarely been reported. In the present article, we report a new mutation (C85R) in exon 3 of the TSH beta-subunit gene in one sporadic case and the mutation Q49stop in two siblings with congenital hypothyroidism. The novel mutation is a T to C transition at codon 85, resulting in a change of cysteine to arginine (C85R) of the ss-subunit. Because the cysteine residues of all glycoproteins are highly conserved, this mutation is expected to result in conformational changes of the ss-subunit, rendering it incapable to form a functional heterodimer with the alpha-subunit. The second mutation described is a C to T transition resulting in a premature stop at codon 49 (Q49stop), leading to the formation of a truncated protein. Although the two siblings reported herein carried the same mutation, they had slightly modified clinical and biochemical phenotype. The mutation C85R and the previously described E11stop have, thus far, exclusively been detected in Greek patients. The Q49stop mutation initially detected in Greek patients was subsequently identified in an Egyptian girl and most recently in two Turkish siblings. These three reports possibly indicate the presence of a mutational hot spot on the TSH beta-subunit gene. Hence, with the novel mutation herein reported, a total of five mutations of the TSH beta-subunit gene are recognized as a cause of low-TSH congenital hypothyroidism worldwide.     

真核翻译始动因子2-a激酶3基因突变致Wolcott-Rallison综合征1例

目的 对Wolcott - Rallison综合征的临床特征及遗传发病机制进行研究.方法 选取临床诊断为Wolcott - Rallison综合征的患儿及其父母为研究对象,运用PCR技术扩增患儿家系真核翻译始动因子2-α激酶3(EIF2AK3)基因的17个外显子区,用DNA直接测序技术,对患儿家系EIF2AK3基因的17个外显子进行基因突变分析.结果 在患儿及其父亲EIF2AK3基因的第9外显子区发现了1个杂合突变(1798A/T),氨基酸序列分析显示这个突变是一种无义突变,可导致EIF2AK3第532位C氨基酸残基形成终止密码子( C532STOP),形成1个532氨基酸残基组成的截短蛋白.患儿母亲EIF2AK3基因未发现相应突变(1798T/T).结论 在中国儿童中,EIF2AK3基因突变可导致Wolcott - Rallison综合征发生.     

西北地区751例新生儿耳聋基因突变筛查

目的初步了解西北地区新生儿常见耳聋基因突变类型和携带率,探讨耳聋基因突变筛查对于辅助诊断和防治新生儿遗传性耳聋的临床价值。方法采集西北地区751例新生儿的足跟血,采用15项遗传性耳聋基因检测试剂盒(微阵列芯片法)对中国人群常见4种耳聋基因15个突变位点进行筛查。结果在751例新生儿中,检测到39例新生儿携带耳聋基因突变,总突变携带率为5.18%。其中GJB2基因突变19例,突变携带率为2.53%;SLC26A4基因突变16例,突变携带率为2.12%;线粒体12SrRNA 1555A>G均质突变4例,突变携带率为0.53%。新疆出生的新生儿279例中,检测到耳聋基因突变11例,突变携带率3.95%;甘肃省出生的新生儿277例中,检测到耳聋基因突变12例,突变携带率4.32%;陕西省出生的新生儿178例中,检测到耳聋基因突变12例,突变携带率6.74%;青海省出生的新生儿17例中,检测到耳聋基因突变4例,突变携带率23.52%。结论西北地区新生儿耳聋基因突变携带率偏高,但是GJB2基因235 del C位点的突变携带率偏低,可能与西北地区的地域特征和人口遗传学特点有关。新生儿耳聋基因筛查对于听力筛查具有很好的互补作用,可以从基因水平发现可能出现迟发性耳聋和药物敏感性耳聋的高危新生儿。     

A Chinese girl with cleidocranial dysplasia (CCD) caused by the recurrent R190W mutation in RUNX 2

OBJECTIVE: Cleidocranial dysplasia (CCD) is a rare skeletal disease with autosomal dominant inheritance associated with mutation in RUNX 2. The authors report a Chinese girl with CCD in whom the mutation in RUNX 2 was identified. METHODS: Clinical diagnosis was based on physical examination, radiological findings, and biochemical tests. For mutation detection, genomic DNA was extracted from peripheral blood using standard method. All 7 coding exons of RUNX 2 and their flanking intronic sequences were amplified by polymerase chain reaction (PCR), and the PCR products were then subjected to automatic DNA sequencing. RESULTS: The affected girl showed typical clinical manifestations of CCD, including patent fontanelles, absent clavicles, short stature and dental anomalies. Direct sequencing of PCR-amplified fragments revealed a recurrent missense mutation, R190W (568 C > T), in RUNX 2. The mutation was further confirmed by Hae III restriction analysis. CONCLUSION: A Chinese case of CCD was confirmed and the disease-causing mutation was linked to a recurrent point mutation in RUNX 2.     

先天性肛门直肠畸形WNT5a基因突变的筛查分析

目的 探讨WNT5a基因突变与先天性肛门直肠畸形(anorectal malformations,ARMs)发生的关系.方法 采用PCR和DNA直接测序的方法,检测88例ARMs患儿和120名健康儿童WNT5a基因第1、2外显子突变情况.结果 3例ARMs患儿存在WNT5a基因第2外显子多点突变,正常对照组未见突变发生.结论 WNT5a基因第2外显子的突变与ARMs可能存在相关性.     

111 例未通过听力筛查新生儿常见耳聋基因突变位点分析

目的了解未通过听力筛查新生儿耳聋基因突变情况。方法随机选取听力筛查未通过、经听觉脑干诱发电位(ABR)测试为感音神经性耳聋患儿111例,收集足跟血血片,提取基因组DNA后,检测GJB2、SLC26A4和线粒体12 Sr RNA基因中的11个热点的突变,分析听力损失程度与突变的关联。结果 111例新生儿中,共检出携带耳聋基因突变24例(21.6%)。其中,GJB 2基因突变14例(12.6%),包括235 del C单杂合突变5例,235 del C和299_300 del AT复合杂合突变5例,以及235del C纯合突变、299_300del AT单杂合突变、176_191del16和235del C复合杂合突变、299_300del AT和508_511 dup AACG复合杂合突变各1例;SLC 26 A 4基因突变10例(9.0%),包括IVS 7-2 AG单杂合突变2例,1226 GA单杂合突变3例,2168 AG单杂合突变2例,IVS7-2AG和2168 AG复合杂合突变3例。本组耳聋患儿中未检出线粒体基因突变。结论未通过听力筛查新生儿中,超过1/5检测到聋基因突变,并以GJB2基因突变最常见,实施热点致聋基因检测可以提高耳聋的病因诊断率。     

一例颅锁骨发育不良患儿的RUNX 2基因突变研究

目的　报告 1中国人常染色体显性遗传颅锁骨发育不良的临床病例并对其致病基因RUNX 2进行突变鉴定。方法　根据患儿的症状、体征、骨骼系统放射线检查和相关血液生化检查进行临床诊断。提取患儿外周血DNA ,PCR扩增RUNX 2编码氨基酸的 7个外显子片段 ,测序检测突变。结果　患儿 ,女 ,5岁 ,具有前囟大、双锁骨缺失、身材矮小、牙齿异常等典型颅锁骨发育不良临床表现。PCR扩增片段直接测序显示患儿RUNX 2外显子 2内发生R190W (5 6 8C >T)错义突变。该突变通过PCR产物的HaeIII限制酶切分析得到进一步确认。结论　报告一例颅锁骨发育不良病例并发现RUNX 2一复发点突变为其致病的遗传基础。     

小儿蚕豆病基因突变的研究

蚕豆病是由于红细胞葡萄糖-6-磷酸脱氢酶缺乏引起的先天性溶血性贫血。我们检测了10例病人及其中5例患者的双亲，结果为6例病人为cDNA1388突变，3例病人为cDNA1376突变，未定型1例。5例患者的双亲均为携带者，其中3例患者的母亲为cDNA1388突变的携带者，2例患者的母亲为1376突变的携带者。说明cDNA1388及1376突变是最常见的突变类型。     

限制型心肌病患儿致病基因检测1例报告

目的分析TNNI3基因变异致可疑限制型心肌病的临床表型及基因型。方法回顾分析1例可疑限制型心肌病患儿的临床资料。结果患儿为4岁8月龄女孩,因咳嗽、发热,心电图异常入院。患儿心电图示双心房负荷重,左心室高电压;超声心动图示全心扩大,室壁运动减弱;心功能不全;少量心包积液;二尖瓣关闭不全(中量反流);肺动脉高压。患儿于入院2个月前曾有上楼时口唇发绀史。基因检测提示患儿存在TNNI 3基因c.575G>A杂合变异,其父母未携带该变异,属于新发变异。该变异使TNNI 3基因192位的精氨酸被组氨酸取代。多物种对比发现该位点具有高度保守性。各种预测软件提示该变异为有害变异。结论TNNI3基因c.575G>A(p.Arg192His)杂合变异很可能是本例患儿的致病变异。     

非典型溶血尿毒综合征分子遗传学研究进展

非典型溶血尿毒综合征是一种罕见的有遗传倾向的疾病,易患基因主要是补体旁路途径活化的调控基因:补体因子H基因、膜辅助蛋白基因和补体因子Ⅰ基因.但其总突变率约为50%,突变类型包括错义突变、无义突变、缺失突变、插入突变和剪切位点突变.遗传方式有常染色体隐性遗传和常染色体显性遗传,显性遗传的三个突变基因均为不完全外显.     

Medium-chain acyl-CoA dehydrogenase deficiency: Molecular aspects

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disorder which is known to cause Reye-like syndrome in children and sudden infant death. A point mutation of lysine329-to-glutamic acid329 substitution in the MCAD gene was recently identified as the most common mutation in patients with MCAD deficiency. This mutation is responsible for about 90% of mutant MCAD alleles in Caucasians. Patients with this type of mutation have a variety of symptoms, indicating that the clinical heterogeneity of MCAD deficiency may not be caused entirely by genetic heterogeneity. Screening for the mutation among newborns in England, Australia, and United States of America indicates the prevalence of carriers to be 1 in 40-107, suggesting the high incidence of the mutation. Since presymptomatic diagnosis and appropriate dietary management are important in MCAD deficiency to prevent life-threatening complications, the relatively high incidence of this disorder may warrant population screening. The most common MCAD mutation can now be detected by DNA diagnostic methods using Guthrie cards. This makes it possible to screen a population efficiently for this potentially fatal disorder.     

The prevalence of mitochondrial gene mutations in childhood diabetes in Japan.

To investigate the prevalence of mitochondrial DNA mutations among Japanese children with IDDM as well as in those with NIDDM, a total of 155 patients with IDDM and 30 patients with NIDDM who were younger than 15 years of age at onset were studied for the following mtDNA mutations: 1) the A-->G mutation at position 3243 of mitochondrial leucine transfer RNA (3243 mutation); 2) the G-->A mutation at position 3316 of mitochondrial leucine transfer RNA (3316 mutation), and 3) The T-->C mutation at position 3394 of the mitochondrial NADH dehydrogenase subunit (3394 mutation). None of the 155 IDDM patients had the 3243 mutation. Although two of the 155 IDDM patients had homoplasmy of 3316 and five had 3394 mutations, these frequencies were not significant compared with healthy controls. None of the 30 NIDDM patients had the 3243, 3316 or 3394 mutation. The presence of these mutations even in control subjects suggests that the effect of the 3316 or 3394 mutation on mitochondrial function is relatively mild. It seems that 3316 and 3394 mutations contribute to the manifestation of diabetes together with other genetic and/or environmental factors.