GABAA受体与脆性X综合征

脆性X综合征(fragile X syndrome,FXS)是引起先天性智力低下的常见疾病,GABAA受体是哺乳动物中枢神经系统内最主要的抑制性神经递质受体,与焦虑、抑郁、癫癎、睡眠、认知等相关.多项研究证明GABA能神经系统特别是GABAA受体的变化与FXS的遗传表型有关.GABAA受体某些亚基的表达变化是FXS患者神经行为学改变的原因之一,可为FXS的治疗提供一个新的方向.     

GABAA受体与脆性X综合征

脆性X综合征(fragile X syndrome,FXS)是引起先天性智力低下的常见疾病,GABAA受体是哺乳动物中枢神经系统内最主要的抑制性神经递质受体,与焦虑、抑郁、癫癎、睡眠、认知等相关.多项研究证明GABA能神经系统特别是GABAA受体的变化与FXS的遗传表型有关.GABAA受体某些亚基的表达变化是FXS患者神经行为学改变的原因之一,可为FXS的治疗提供一个新的方向.     

脆性X综合征

1969年Lubs首先报告了X连锁智力低下与X染色体脆性位点(fragile site)有关。人类fra(Xq27)是指X 染色体长臀末端2区7带的断裂或随体样改变。具有这些改变的X 染色体称脆性X 染色体(简称脆性X)。脆性X 在严重智力低下的男性中占7%;在轻微智力低下的男性中占4.5%。国内1984年许碧珍等首次报告本病,1985年周宪庭等报告北京及沈阳估计发病率分别为     

脆性X综合征的临床及细胞遗传学研究：附两家系分析

应用FUdR及Caffein诱导方法检出两家族共8例脆性X综合征患者,4例携带者。指出,智力低下伴多动、大耳朵及不明原因的癫病发作是青春期前患者进行脆性X检查的临床指征。     

智力低下和孤独症男童脆性X基因突变的研究

目的应用改良基因检测方法,探讨脆性X综合征致病基因(fragileXmentalretardation"1,FMR1)在中国人群智力低下和孤独症中的作用。方法收集2002～2006年小儿神经、遗传代谢门诊诊断的男性孤独症患儿44例、非家族性智力低下男性患儿40例,建立适用于男性的FMR1基因突变检查方法,对检查阳性者以pfxa3探针进行Southern杂交。结果在44例孤独症患儿中,发现1例pfxa3杂交片段约0.2kb,为FMR1前突变;40例智力低下患者中FMR1基因未见异常。结论在孤独症人群中发现的1例FMR1基因前突变,其致病意义有待进一步阐明。     

脆性X染色体综合征癫(癎)发作机制研究进展

脆性X染色体综合征(fragile X syndrome, FXS)是一种X连锁不完全显性遗传病,男性发病率为1/4000,女性为1/6000[1],具有一种特殊的Sherman遗传现象,即FXS在家系内患病风险呈逐代递增趋势,而在兄弟姐妹中患病风险率较低的一种遗传现象.     

脆性X智力低下蛋白的研究进展

脆性X综合征是最常见的遗传性智力低下性疾病之一，临床表现及贵传方式都有其独特之处，研究发现，家族性智力低下蛋白的缺乏在本病的发病中起重要作用。本文从该蛋白的结构、分布、功能、与学习记忆的关系及其在诊断中的应用等几个方面进行综述。     

脆性X综合征的筛查与诊断

脆性Ｘ综合征是引起先天性智力低下常见疾病，仅次于Ｄｏｗｎ综合征，由家族性智力低下基因（ＦＭＲ）－１动态突变引起，具有独特的遗传方式和临床表现，本文综述了疾病有关细胞遗传学，分子生物学和免疫细胞化学方面的筛查及诊断方法。     

脆性X综合征的筛查、诊断和治疗

目的 为简化筛查标准，提高对脆性X综合征（FRAXA）筛查、诊断和治疗能力。方法 采用九条标准，智力低下、智力低下家族史、长脸、（或突出）耳朵、注意力不集中及多动、孤独行为、通贯掌、巨睾和关节过度伸展。对208例可疑FRAXA（男190例，女18例）的筛查进行回顾性分析。用PCR方法扩增（CGG）n三核苷酸重复序列作筛查，对PCR－Southern杂交作诊断；用叶酸及早期干预进行治疗。结果 用PCR－Southern杂交法诊断FRAXA7例。分析通贯掌、巨睾及关节过度伸展在FRAXA的筛查中出现的频率低，与诊断相关不甚密切，故采用简化的六项标准，如果评分≥6分，应作进一步检测；评分＜6分，60％以上的病例可以除外FRAXA，且不遗漏任何阳性病例。对6／7例用叶酸进行治疗，治疗有效，未发现副作用。结论 简化的六项标准明显提高了FRAXA的临床筛查的阳性率；而PCR方法快捷、简便，适用于FRAXA的筛查。叶酸治疗此综合征有效。     

脆X综合征的分子基础及其认知研究进展

脆X综合征(FXS)由于存在X染色体CGG重复片段大量扩增,导致脆X智力低下基因异常甲基化,基因失活,脆X智力低下蛋白生成障碍,因嵌合体或X染色体活化率不同,引起不同程度的脆X智力低下蛋白降低和神经元与突触的生成与成熟障碍,导致学习与记忆功能异常.FXS的特殊认知表型与其分子基础有关,FXS具有不同程度认知功能的异常,主要有视觉空间能力、注意力、工作记忆及执行功能异常,而执行功能异常认为是其特殊的认知基础.     

Lessons from fragile X regarding neurobiology, autism, and neurodegeneration

The fragile X mental retardation 1 gene (FMR1) mutation causes two disorders: fragile X syndrome (FXS) in those with the full mutation and the fragile X-associated tremor/ataxia syndrome (FXTAS) in some older individuals with the premutation. FXS is caused by a deficiency of the FMR1 protein (FMRP) leading to dysregulation of many genes that create a phenotype with ADHD, anxiety, and autism. FXTAS is caused by the elevation of FMR1-mRNA to levels 2 to 8 times normal in the premutation. This causes an RNA gain of function toxicity leading to brain atrophy, white matter disease, neuronal and astrocytic inclusion formation, and subsequent ataxia, intention tremor, peripheral neuropathy, and cognitive decline. The neurobiology and pathophysiology of FXS and FXTAS are described in detail.     

Screening for fragile X syndrome: results from a school for mentally retarded children

Fragile X syndrome is the most common inherited form of familial mental retardation. The purpose of this study was to identify yet unrecognized fragile X individuals and to estimate the frequency of both the FRAXA and FRAXE forms of the disease in a population of mentally retarded children attending a special school in Croatia. The results are reported of molecular screening of 114 children with mild to severe mental retardation. Three individuals (2.6%) with the FRAXA form of the fragile X syndrome and one boy (0.9%) with FRAXE mental retardation were detected; a total of four newly diagnosed fragile X families were identified. Closer clinical examination revealed that behavioural and speech disturbances were clearly present among all fragile X cases (both FRAXA and FRAXE), indicating that these features could be additional diagnostic criteria for the preselection of individuals at risk.

Conclusion: Fragile X screening among mentally retarded children attending a special school should be highly encouraged to reveal the cause of mental retardation and to detect yet unrecognized fragile X individuals. The frequency of fragile X syndrome in a such population in Croatia was found to correlate with similar results from previous studies. However, since at the time of diagnosis all affected families had a second or even a third child born, earlier diagnosis should be considered to provide greater benefit to fragile X families.     

Attention across modalities as a longitudinal predictor of early outcomes: the case of fragile X syndrome

Background: Fragile X syndrome (FXS) is an early diagnosed monogenic disorder, associated with a striking pattern of cognitive/attentional difficulties and a high risk of poor behavioural outcomes. FXS therefore represents an ideal model disorder to study prospectively the impact of early attention deficits on behaviour. Methods: Thirty‐seven boys with FXS aged 4–10 years and 74 typically developing (TD) boys took part. Study 1 was designed to assess visual and auditory attention at two time‐points, 1 year apart. Study 2 investigated attention to multimodal information. Both tested attention markers as longitudinal predictors of risk for poor behaviour in FXS. Results: Children with FXS attended less well than mental‐age matched TD boys and experienced greater difficulties with auditory compared to visual stimuli. In addition, unlike TD children, they did not benefit from multimodal information. Attention markers were significant predictors of later behavioural difficulties in boys with FXS. Conclusions: Findings demonstrate, for the first time, greater difficulties with auditory attention and atypical processing of multimodal information, in addition to pervasive global attentional difficulties in boys with FXS. Attention predicted outcomes longitudinally, underscoring the need to dissect what drives differing developmental trajectories for individual children within a seemingly homogeneous group.     

Social behavior and cortisol reactivity in children with fragile X syndrome

OBJECTIVE: To examine the association between limbic-hypothalamic-pituitary-adrenal (L-HPA) axis reactivity and social behavior in children with fragile X syndrome (FXS). METHOD: Salivary cortisol changes and concurrent anxiety-related behaviors consistent with the behavioral phenotype of FXS were measured in 90 children with the fragile X full mutation and their 90 unaffected siblings during a social challenge task in the home. RESULTS: Boys and girls with FXS demonstrated more gaze aversion, task avoidance, behavioral signs of distress, and poorer vocal quality than the unaffected siblings. Multiple regression analyses showed that after accounting for effects of IQ, gender, age, quality of the home environment, and basal cortisol level, cortisol reactivity to the task was significantly associated with social gaze in children with FXS. The most gaze-aversive children with FXS had cortisol reductions, whereas those with more eye contact demonstrated the most cortisol reactivity. Unaffected siblings demonstrated an opposite pattern in which less eye contact was associated with increased cortisol reactivity. CONCLUSIONS: Results of the study suggest a unique relation between abnormal gaze behavior and L-HPA mediated stress reactivity in FXS.     

Psychopathology and familial stress - comparison of boys with Fragile X syndrome and spinal muscular atrophy

BACKGROUND: Chronic illness and mental retardation are both associated with an increased rate of behavioural problems in children and with considerable emotional strain in families. The aim of the study was to analyse and compare the specific effects of two exemplary conditions on familial stress and coping. METHODS: Forty-nine boys with Fragile X syndrome (FXS) were compared with 46 boys with Spinal Muscular Atrophy (SMA) and 32 male controls. Intelligence was measured with the RAVEN or K-ABC tests. Psychopathology was assessed with the CBCL questionnaire and a structured psychiatric interview (Kinder-DIPS), parental stress with the QRS, coping with the F-COPES and social support with the F-SOZU questionnaires. RESULTS: The mean age of the FXS boys was 8.6, of the SMA boys 12.7 and of the controls 11.2 years. The mean IQ was 47 for the FXS, 112 for the SMA and 103 for the control groups. According to the CBCL, 89.8% of the FXS boys, 21.7% of the SMA and 15.7% of the controls had a total score in the borderline or clinical range. The rates were 63.3%, 34.8% and 21.9% for internalising and 67.3%, 10.9% and 18.8% for externalising behaviour, respectively. 81.6% of the FXS and 10.9% of the SMA patients had a DSM-IV or ICD-10 psychiatric diagnosis. The most common were ADHD (FXS: 36) and Separation Anxiety Disorder (SMA: 4). In total, parental stress was significantly higher in the FXS than in the SMA families (and in both compared to controls). There were no major inter-group differences regarding social support and familial coping. CONCLUSIONS: Children with FXS are severely mentally retarded and have a high rate of mainly externalising disorders. Despite good coping abilities and social support, this is associated with high familial stress. The SMA boys, with an intelligence in the upper normal range, are no more deviant than their healthy controls. Parental stress is lower in the SMA families with good coping abilities. In conclusion, families with mentally retarded children are in even greater need of help than those of children with severe chronic illness/physical handicap.     

Effect of the deficits of fragile X mental retardation protein on cognitive status of fragile x males and females assessed by robust pedigree analysis

The effect of the fragile X mental retardation 1 (FMR1) gene product (fragile X mental retardation protein [FMRP]) deficits on Full-Scale IQ (FSIQ) and FSIQ-adjusted Wechsler subtests and index scores in fragile X disorder were assessed using a robust modification of the maximum likelihood estimators for pedigree data. The results from 144 extended families have demonstrated a linear effect of progressively reduced levels of FMRP on the FSIQ and all subtest and summary scores in either gender. The effect of FMRP in decreasing FSIQ-adjusted subtest scores was highly significant for Digit Span, Symbol Search, Object Assembly, and Picture Arrangement, with a consistent trend in both genders. Heritability for FSIQ and unadjusted subtest scores estimated from the covariance model did not exceed 50% and varied widely from the highest for Verbal score to the lowest for Picture Completion score. Possible mechanisms by which FMRP deficit impacts on specific weaknesses in fragile X are considered on the basis of present data.     

Autistic spectrum disorder and the fragile X premutation

Fragile X syndrome (FXS) is the most common inherited cause of mental retardation. It is also one of the most common identifiable causes of Autism Spectrum Disorder (ASD). Carriers of FXS are often considered to be cognitively and behaviorally unaffected. However, we report here on six individuals in the premutation range who also have ASD. A comparison is made with five subjects in the premutation range who did not receive a diagnosis of ASD. The six individuals with ASD had a range of cognitive ability levels from no impairment to moderate retardation. Discussion includes the impact of molecular variables including lowered FMR1 protein and elevated FMR1 mRNA in addition to environmental factors leading to the complex neurodevelopmental disorder of ASD.