Salla disease variant in a Dutch patient

A Dutch child with psychomotor retardation, impaired speech, ataxia, sialic acid storage and vacuolized skin fibroblasts and lymphocytes was diagnosed as having free sialic acid storage disease. Slight corneal opacities, pale optic disks at the fundus oculi and vertebral abnormalities, not earlier reported in Salla disease, were peculiar to this case. Free sialic acid was about tenfold increased in urine and cultured fibroblasts, without changes in the glycoconjugate-bound sialic acid pool. A subsequent pregnancy of the patient's mother was monitored by assay of sialic acid in chorionic villi and amniotic fluid. An unaffected foetus was predicted. Sialic acid was also assayed in peripheral blood total leucoyctes, and in mononuclear and polymorphonuclear (PMN) leucocyte subpopulations. Each of these leucocyte fractions from the patient showed 10- to 30-fold increase in sialic acid content. The PMN subpopulation provided the most restricted range of control values and showed slightly increased values for the patient's parents. These results suggest that the assay of sialic acid in PMN might be useful for the identification of heterozygotes in sialic acid storage disease. Studies on a larger number of obligate heterozygotes are needed to confirm this observation.     

串联质谱技术对苯丙酮尿症杂合子的检测

目的建立串联质谱技术测定血苯丙氨酸(Phe)和酪氨酸(Tyr)浓度方法,观察苯丙酮尿症(PKU)、PKU杂合子和正常对照组血Phe、Tyr浓度及其比值(Phe/Tyr)变化。方法研究对象为52例PKU患儿,152例PKU杂合子成人,160名正常成人作为对照。研究方法采用干血滤纸片法,血滤纸片经含已知浓度Phe和Tyr内标的甲醇萃取,盐酸正丁醇衍生后,用串联质谱仪分析。结果(1)样品回收率Phe在346μmol/L和485μmol/L浓度时分别为102%和100%,Tyr在276μmol/L和442μmol/L浓度时分别为103%和98%。(2)批内CVPhe为6.7%,Tyr为10.5%,批间CVPhe为12.2%,Tyr为9.9%。(3)PKU患者血Phe、Tyr浓度和Phe/Tyr值分别为(634.0±300.3)μmol/L、(41.9±16.3)μmol/L和16.5±9.9,PKU杂合子分别为(68.3±21.4)μmol/L、(40.1±11.8)μmol/L和1.7±0.4,对照组分别为(53.2±10.2)μmol/L、(43.6±9.5)μmol/L和1.2±0.2。PKU患者血Phe、Phe/Tyr值与PKU杂合子、对照组比较差异有统计学意义(P<0.01)。PKU杂合子与对照组比较,Phe、Phe/Tyr水平较高(均P<0.01),Tyr水平较低(P<0.01)。结论串联质谱技术能够准确测定干血滤纸片中Phe和Tyr浓度。PKU杂合子Phe浓度和Phe/Tyr值高于正常成人,但与正常人有明显的重叠。     

Is dystrophin present in the nerve terminal nat the neuromuscular junction? An immunoshistochemical study of the heterozygote dystrophic (mdx) mouse

Neuromuscular junctions (NMJs) were identified by revealing the presence of cholinergic receptors (AChR) with alpha-bungarotoxin coupled to the fluorescent dye cascade blue in 9- and 60-day-old normal and heterozygote mdx mice. Dystrophin was detected by an immunoperoxidase technique. All the muscle fibers of the normal animals observed in cross sections were immunoreactive for dystrophin and an accumulation of dystrophin was observed at all NMJs identified by alpha-bungarotoxin. In the 9-day-old mdx heterozygote animals, dystrophin positive, negative, and partially positive muscle cross sections were observed. Four different observations were made in these heterozygote animals on the coexistence of AChR and dystrophin. First, alpha-bungarotoxin sites (i.e., NMJs) were observed on dystrophin positive muscle fiber cross sections with an accumulation of dystrophin at these sites. Second, alpha-bungarotoxin sites were observed on dystrophin positive fibers without a dystrophin accumulation at NMJs. Third, there was a coexistence of alpha-bungarotoxin and dystrophin labelling at NMJs of muscle fibers with perimeters labelling negative for dystrophin. Fourth, NMJs, identified by alpha-bungarotoxin, were observed on muscle fibers negative for dystrophin even at the NMJ. These observations suggest that dystrophin is present not only in the muscle membrane but also in the presynaptic nerve terminals.     

Neuropathological study on cerebellum of macular mutant mouse heterozygote

The hemizygote of the macular mutant mouse is clinically, biochemically and neuropathologically similar to a patient with Menkes kinky hair disease. The heterozygote of this mutant mouse was biochemically and neuropathologically examined. The copper content in the brain decreased in comparison with that in the normal littermate, although it was more than that in the hemizygote. In the Golgi study, abnormal Purkinje cells with somal sprouts, thick stem dendrites and dendritic focal swellings, which were seen in the hemizygote, were not observed in the heterozygote. Ultrastructurally, abnormal mitochondria were seen in the Purkinje cells in the anterior and middle cerebellar lobe of the heterozygote. Histochemically, cytochrome c oxidase activity decreased, especially at the anterior lobe in the cerebellar cortex of the heterozygote. This activity, as indicated by staining intensity, was in between that in the normal littermate and that in the hemizygote. The heterozygote did not show a mosaic pattern in the distribution of these neuropathological changes, although this mutant mouse shows x-linked recessive inheritance. Thus, our results lead to the conclusion that the neuropathological changes observed in this mutant mouse do not result directly from an abnormal gene in the Purkinje cell, but from the secondary effects subsequent to presumptive copper deficiency.     

角膜营养不良与BIGH3基因突变研究

对角膜营养不良患者进行分子遗传学分析,探讨我国人角膜营养不良中BIGH3基因突变的类型。方法2000年7～12月收集15例颗粒状、Avellino、Reis-Bācklers角膜营养不良患者和5例无任何角膜病变的正常对照者外周血10ml,提取白细胞DNA,利用合成的BIGH3基因第4和第12外显子特异性引物,进行PCR扩增,并对扩增产物进行直接测序,分析相应基因序列。结果15例患者均检出BIGH3基因突变,其中R124H突变10例,包括纯合子2例,杂合子8例;R124L突变2例,均为杂合子;R555W突变3例,均为杂合子;正常对照者均未检出BIGH3基因突变。结论15例角膜营养不良患者的角膜病变均由BIGH3基因突变引起,与国外文献报道相同。突变基因对角膜病变严重程度的影响具有剂量效应,纯合子病情严重。R124L突变患者的临床表现重于R124H突变患者。     

两种新型Wiskott-Aldrich综合征蛋白基因突变的鉴定

目的 明确3例Wiskott-Aldrich综合征(WAS)患儿WAS蛋白(WASP)基因突变的类型。方法 根据典型临床表现(血小板减少、湿疹、反复感染),及淋巴细胞和血小板扫描电镜改变,采用PCR直接测序法,对3例疑为WAS的患儿及其母亲的WASP基因进行序列分析。结果 以正义、反义引物扩增的PCR产物分别测序,发现两种新型WASP基因突变：2例WAS孪生兄弟WASP基因第10外显子,第984位核苷酸C缺失突变(984delC),导致317位密码子后移码突变,于444位密码子提前出现终止密码(H317fsX444);其母亲为此突变WASP基因携带者。另l例WAS患儿WASP基因第ll外显子,第1388位核苷酸由G替换为T(1388G→T),为无义突变,使第452位密码子提前变为终止密码(E452X)。其母亲无此突变WASP基因。结论 鉴定出两种新型WASP基因突变,WASP基因序列分析对于不典型和散发WAS的诊断及WASP突变基因携带者的检出有重要作用。     

SMN基因缺失多重连接探针扩增法检测和识别脊柱肌肉萎缩症的纯合型或杂合型SMN基因缺失

Objective: Spinal muscular atrophy(SMA), an autosomal recessive neuromuscular degen-eration of the anterior horn ceils of the spinal cord and brain stem, results in one of the most common dis-eases with muscle fatigue and atrophy. Most SMA cases including all the types are due to the homozygous deletion of at least exon 7 within the survival motor neuron 1 (SMN-1) gene. Although a ““golden stand-ard““ assay ( PCR with mismatch primer followed by enzyme digestion) is very reliable for the identifica-tion of homozygous SMN-1 deletion, the carrier detection of heterozygous SMN-1 deletion remains a chal-lenge. Methods: Some PCR-based gene dosage assays or multiplex PCR allow for the determination of the copy number of SMN-1 gene to identify heterozygous deletion, but these procedures are often time consuming and available on a limited clinical basis. Recently developed MLPA (multiplex ligation-de-to establish the copy number of the SMN gene. We performed a validation for simultaneous detection of homozygous SMN-1 deletions of SMA patients and heterozygous SMN-1 deletions of SMA carriers in a sim-ple assay using a MLPA-SMA assay specific reagent. Results: Six out of 20 patients with SMA were found to have homozygous SMN-1 deletion, confirmed by the PCR/digestion assay. All 4 parents of the children with SMA had heterozygous SMN-1 deletion, confirmed by an independent relative quantitative analysis. Conclusion: MLPA provides a simple, rapid and accurate method of simultaneously detecting homozygous deletions and heterozygous deletions in a sinzle assay for both SMN-1 and SMN-2 zenes.     

地中海贫血高风险胎儿的产前基因诊断

目的　探讨地中海贫血 (简称地贫 )高风险胎儿宫内基因诊断的价值。　方法　 12 8例地中海贫血高风险胎儿于妊娠中期抽取羊水 10～ 2 0 ml或脐血 1m l进行基因诊断。　结果　 12 8例被检胎儿中基因正常 32例 ,α地贫缺失杂合子 38例 ,纯合子 2 7例 ;β地贫单一突变杂合子 18例 ,纯合子 4例 ,双重杂合子 9例 ;β地贫基因突变类型及频率依次为 :CD41- 42 (47.5 % ) ,IVS- - 6 5 4(42 .5 % ) ,CD17(A- T) (7.5 % )及 - 2 8(A- G) (2 .5 % )。无一例发生严重母胎并发症 ,重型地贫胎儿 40例均在知情同意前提下及时终止妊娠。　结论　筛查地贫高风险胎儿并及时进行产前基因诊断安全、有效、准确。在地贫高发区域 ,应作为常规产科检测方法。     

Partial ornithine transcarbamylase deficiency in females: diagnosis by an immunohistochemical method

Females heterozygous for the X-linked urea cycle disorder, ornithine transcarbamylase (OTC) deficiency have a significant risk of developing hyperammonaemia. Diagnosis of this genetic defect in a proband is the essential starting point for family studies. By an immunohistochemical analysis of the liver specimens fixed in 10% formalin, we confirmed heterozygous status for OTC deficiency in two female patients, a 15-year-old girl and a 2-year-old girl, who died of hyperammonaemia. Since most affected males lack cross reactive materials (CRM), an immunochemical analysis should be useful for the diagnosis of most heterozygous females.Abbreviations OTC ornithine transcarbamylase - CRM cross reactive materials - RFLPs restriction fragment length polymorphisms - CPS I carbamylphosphate synthetase I