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.     

遗传性痉挛性截瘫一家系的临床特点与遗传学分析

目的 探讨遗传性痉挛性截瘫(HSP)一家系的基因型和临床特点.方法 抽取1个HSP家系15名成员外周血,选择与已知HSP致病基因位点在物理距离上紧密连锁的微卫星分子进行标记[短串联重复序列(STR)],连锁分析并构建单体型.对患者进行观察,行心肌酶学、肌电图以及头颅、颈髓、胸髓MRI检查,总结其临床特点.结果 家系成员SIR的扩增产物进行基因分型,连锁分析发现与HSP 31型(SPG31)位点连锁,2个SIR(D2S2951、D2S2333)最大LOD值为1.8,表明连锁.经过连锁分析后得到的对应致病基因为REEP1基因,经过突变筛查发现了1个REEP1 c417+1G＞A杂合突变.SPG31临床特点以痉挛步态、下肢肌张力增高为主要表现,MRI显示胸髓萎缩.结论 SPG31患者临床特征表现为典型的HSP特征,致病基因为REEP1基因,存在REEP1 c417+1G＞A杂合突变.     

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.     

An activated renin-angiotensin system maintains normal blood pressure in aryl hydrocarbon receptor heterozygous mice but not in null mice

It has been postulated that fetal vascular abnormalities in aryl hydrocarbon receptor null (ahr^−/−) mice may alter cardiovascular homeostasis in adulthood. We tested the hypothesis that blood pressure regulation in adult heterozygous mice (ahr^+/−) would be normal, compared to ahr^−/− mice, since no vascular abnormalities have been reported in the heterozygote animals. Mean arterial blood pressure (MAP) was measured using radiotelemetry prior to and during treatment with inhibitors of the autonomic nervous system, nitric oxide synthase (NOS), angiotensin converting enzyme (ACE), or endothelin-1 A receptor (ET_A). Also, indices of renin-angiotensin system (RAS) activation were measured. ahr^+/− and ahr^−/− mice were normotensive and hypotensive, respectively, compared to wild-type (ahr^+/+) littermates. Responses of all genotypes to autonomic nervous system inhibition were normal. ahr^+/− mice responded normally to NOS inhibition, while the responses of ahr^−/− mice were significantly blunted. In contrast, ahr^+/− mice were significantly more responsive to inhibition of ACE, an ET_A antagonist, or both, while ahr^−/− mice were significantly less responsive to ACE inhibition and more responsive to an ET_A antagonist. ahr^+/− mice also exhibited significant increases in plasma renin and ACE activity, plasma sodium, and urine osmolality, indicative of RAS activation. Thus, normotension in ahr^+/− mice appears to be maintained by increased RAS and ET-1 signaling, while hypotension in ahr^−/− mice may result from decreased RAS signaling. In conclusion, despite the lack of overt fetal vascular abnormalities in ahr^+/− mice, the loss of a single ahr allele has a significant effect on blood pressure regulation.     

原发性肝细胞癌1号染色体杂合子丢失的初步研究

目的 分析原发性肝细胞癌（ＨＣＣ）１号染色体短臂（１ｐ）上１０个位点等位基因杂合子丢失（ＬＯＨ）,以期寻找１ｐ上可能存在的与ＨＣＣ发生有关的肿瘤抑制基因的缺失区域。方法 用聚合酶链反应（ＰＣＲ）方法分析３８例ＨＣＣ的１号染色体短臂１０个位点微卫星多态性标记的ＬＯＨ。所有患者均做ＨＢＶ５项检测和ＨＣＶ血清抗体的ＥＬＩＳＡ法检测。结果 在８４．２％（３２／３８例）的ＨＣＣ组织中检出染色体１ｐ片段的ＬＯ     

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。     

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。     

α和β地中海贫血双重杂合子的基因诊断

目的 :探讨α和β地中海贫血双重杂合子的基因诊断。方法 :采用跨越缺失区断裂点的PCR方法检测α 地中海贫血 1基因。采用等位基因特异寡核苷酸探针 /反向点杂交 (ASO/RDB)技术检测 β 地中海贫血基因。 结果 :对地中海贫血筛查中发现的 3例疑为α和β地中海贫血双重杂合子进行基因诊断 ,均属于东南亚缺失型α 地中海贫血 1和β 地中海贫血双重杂合子 ,其中 1例为α 地中海贫血 1和β 2 8(A→G) ,1例为α 地中海贫血 1和βIVS Ⅱ 6 5 4 (C→T) ,1例为α 地中海贫血 1和HbE。结论 :α和 β地中海贫血双重杂合子的检出对临床准确进行地中海贫血的产前诊断有重要意义。