脆性X相关的震颤/共济失调综合征

脆性X相关的震颤/共济失调综合征是一种累及多系统的神经功能障碍性疾病.它对广大临床医生是一个全新的概念,对脆性X相关的震颤/共济失调综合征的有关知识的认识,能够对该综合征作出正确的诊断.下面就对脆性X相关的震颤/共济失调综合征的分子基础、基因检测、临床表现、特征性的影像学及病理学表现等方面的一些研究进行了综述.     

精神发育迟滞患者的X染色体脆性位点和 FMR-1基因突变的研究

目的探讨精神发育迟滞患者病因的检测方法。方法采用细胞遗传学方法检测Ｘｑ２７脆性位点,利用ＰＣＲ法检测ＦＭＲ－１基因突变。结果１０８８名精神发育迟滞患者中有１１２名为脆性Ｘ综合征［Ｆｒａ（Ｘ）］患者,９７％的Ｆｒａ（Ｘ）有ＦＭＲ－１基因突变。结论细胞遗传学方法和ＰＣＲ法结合运用,可准确有效地诊断出脆性Ｘ综合征患者     

伴有癫痫的脆性X综合征家系1例

脆性X综合征（fragile X syndrome,FXS）是FMR1基因CGG异常重复扩增导致的疾病。本文报告1对经基因检测诊断为FXS的兄弟,2例患者分别为15岁和14岁,均存在语言障碍、智力障碍、注意力缺陷障碍、孤独症谱系障碍和FXS特征性面容等临床表现,其中先证者伴有罕见的晚发性癫痫发作,经左乙拉西坦治疗效果良好,而其弟弟经反复随访未见脑电图异常。该对病例提示FXS临床表型具有多样性和异质性。     

脆性X智力低下一号基因缺陷对环磷酸腺苷的影响

目的探讨脆性X智力低下一号基因(FMR1)表达缺失对环磷酸腺苷(cAMP)的影响及其机制。方法通过硝普钠封闭FMR1，建立脆性X综合征细胞模型；研究FMR1表达缺失对cAMP水平及cAMP代谢途径中的两个关键酶[腺苷酸环化酶(AC)及磷酸二酯酶(PDE)]活性的影响。结果在细胞水平，硝普钠可成功地封闭FMR1基因；基因封闭组细胞内cAMP水平明显低于对照组(P=0．000)；该组腺苷酸环化酶的比活力明显低于对照组(P=0．000)，而磷酸二酯酶比活力则无显著改变(P=0．983)。结论FMR1基因表达缺失可导致细胞内cAMP的水平降低，腺苷酸环化酶活性被抑制可能是其降低的原因之一。     

LIMK1mRNA及其蛋白在脆性X综合征小鼠大脑皮层中的表达

目的 观察LIMK1 mRNA及其蛋白在脆性X综合征(FXS)小鼠大脑皮层中的表达,探讨其在FXS发病机制中的作用.方法 选择雄性FMR1基因敲除型FVB近交系新生鼠和2、4、6周小鼠做为实验组(记为 KO0d、KO2W、KO4W和KO6W),雄性同龄野生小鼠(WT)作为对照组(记为WT0d、WT2W、WT4W和WT6W),每组每时间点9只.取小鼠单侧大脑皮层行LIMK1 mRNA实时荧光定量PCR分析,取另一侧大脑皮层行LIMK1蛋白Western blotting分析.结果 (1)KO6W组小鼠LIMK1 mRNA含量较同龄组WT小鼠及KO0d、KO2W和KO4W组小鼠明显升高,WT0d组小鼠LIMK1mRNA含量明显高于WT2W、WT4W和WT6W组小鼠,差异有统计学意义(P<0.05).(2)同龄KO、WT小鼠大脑皮层中LIMK1蛋白含量差异无统计学意义(P>0.05);KO0d组小鼠LIMK1蛋白含量明显低于KO2W、KO4W和KO6W组,WT0d组小鼠大脑皮层中LIMK1蛋白含量明显低于WT2W、WT4W和WT6W组,差异有统计学意义(P<0.05).结论 LIMK1蛋白的翻译过程在6周时受到明显抑制,反馈性调节转录过程使LIMK1 mRNA表达急剧升高.KO鼠LIMK1蛋白表达下降,从而影响树突棘的骨架蛋白重构,影响树突棘的功能改变,可能是FXS神经系统改变的重要机制之一.

Abstract：

Objective To observe the mRNA and protein expressions of LIMK1 in the cerebral cortex of mice with FMR1 gene knockout, and explore the roles of LIMK1 mRNA and LIMK1 protein inthe pathogenic mechanism of fragile X syndrome (FXS). Methods FVB strain male mice with FMR1 gene knockout (KO, n=36, experimental group) and their wild type (WT, n=36, control group) were equally divided into 8 counterpart subgroups (WT0d, WT2W, WT4W, WT6W, KO0d, KO2W, KO4W and KO6W),respectively, according to different ages. LIMK1 mRNA expression in the left sides of the cerebral cortex were analyzed with RT-qPCR and protein expression of LIMK1 in another side with Western blotting.Results No significant differences of LIMK1 mRNA expression in the cerebral cortex of KO0d, KO2Wand KO4W subgroups were noted as compared with that of respective age-matched WT mice (P>0.05);but that of KO6W subgroup was significantly increased as compared with that of WT6W subgroup, and KO0d,KO2W and KO4W subgroups (P<0.05);the level of LIMK1 mRNA in WT0d subgroup was obviously higher than that of WT2W, WT4W and WT6W subgroups (P<0.05). No statistic differences of LIMK1 protein between the same-age KO and WT mice were noted (P>0.05);significantly lower level of LIMK1 protein in KO0d subgroup was found as compared with that of KO2W, KO4W and KO6W subgroups (P<0.05);that of WT0d subgroup was lower than that of WT2W, WT4W and WT6W subgroups (P<0.05). Conclusion The translation process of LIMK1 protein is significantly inhibited at 6 weeks and LIMK1 mRNA expression increased sharply based on the feedback adjustment of LIMK1 protein expression declining;once this translation process is inhibited or interrupted, it will affect the dendritic spines skeleton protein reconstruct and lead to the dendritic spines function deficient;the inhabitation of translation process might probably play an important role in the process of dendritic spines maturation and should be an important pathogenic mechanism of FXS.     

CaMKⅡα在FMR1基因敲除小鼠脑组织中的表达

目的 观察FMRI基因敲除型(KO)小鼠脑组织中钙/钙调素依赖蛋白激酶Ⅱα(CaMKⅡα)表达的改变,探讨CaMKⅡα是否为脆性X综合征相关蛋白(FMRP)的下调蛋白. 方法 PCR鉴定FVB近交系小鼠的基因型,按基因型的不同分为KO组和野生型(WT)组,每组10只.免疫组化染色检测KO及WT小鼠脑组织CaMKⅡα的表达与分布,用图像分析仪分别采集不同脑区免疫信号的吸光度(A)值进行比较. 结果 免疫组化染色检测显示KO与WT小鼠各个脑区普遍存在阳性信号;神经元胞浆尤其是靠近胞体的近端突起上信号呈强阳性,树突中亦有阳性信号,轴突上信号较弱;KO小鼠各脑区CaMKⅡα阳性信号的A值均较WT小鼠显著增高,差异有统计学意义(P＜0.05). 结论 CaMKⅡα在成年KO小鼠各脑区的表达均显著增多,提示FMRP负性调节CaMKⅡα的表达.     

实时荧光定量聚合酶链反应检测腓骨肌萎缩症1A型基因重复

腓骨肌萎缩症（Charcot-Marie-Tooth disease,CMT）,是神经系统常见的遗传性疾病之一,根据电生理和病理学研究将其分成两大组：CMT1（脱髓鞘型）和CMT2（神经元型或称轴索型）.该病是一组遗传异质性疾病,目前已发现30个基因座位与不同类型的CMT相关,其中有11型已明确了致病基因,发病率最高的是常染色体显性遗传的CMT1A.我们已先后建立起短串联重复序列分析（STR）和聚合酶链反应（PCR）酶切法检测特异性融合片段来诊断CMT1A基因重复.STR结合银染的方法因有便宜、省时和所需DNA数量少等优点曾被广泛应用,但主要缺点是受杂合率的限制,如果被检测者为纯合子,则无法得出结论;再者,实验结果不稳定,银染重复性不理想.而PCR酶切法的阳性率则较低.因此,为提高基因重复检测的阳性率,并适于在临床应用,我们应用实时荧光定量PCR技术,以SYBRGreen Ⅰ荧光染料为标记物,采用标准曲线的相对定量方法检测了18例CMT1A患者的基因重复,现报道如下.