不宁腿综合征遗传学研究进展

不宁腿综合征(Restless legs syndrome, RLS)遗传学研究近年来获得了许多重要的进展, 极大地丰富了对于这种疾病分子机制的认识。RLS是一种常见的复杂疾病, 几个遗传流行病学和双生子研究对RLS遗传组分进行了剖析, 说明RLS是一个遗传性很强的性状, 其遗传力约为50%。采用基于模型的连锁分析方法或者是不依赖于模型的连锁分析方法目前已定位了5个重要的RLS疾病连锁位点: 12q13-23, 14q13-21, 9p24-22, 2q33和20p13, 为定位克隆RLS致病基因或者易感基因提供了连锁图谱。最新基于高通量的SNPs分型平台开展的全基因组分析确立3个与RLS显著关联的区域: 6p21.2, 2p14和15q23。文章结合作者近年来从事不宁腿综合征遗传学的研究工作, 对该领域的重要成果进行了汇总和评述。     

一个非综合征性耳聋家系致病基因的研究

非综合征性耳聋(nonsyndromic hearing impairment, NSHI)是一种十分常见的人类神经系统疾病, 约有1/1000的新生儿患有语前聋。GJB2基因编码间隙连接蛋白Cx26, 是最常见的NSHI致病基因, 大约50%的常染色体隐性遗传NSHI是由GJB2基因突变引起的。在本研究中, 收集了江苏省一个复杂的非综合征性耳聋家系, 并对其进行了分子遗传学研究。对所有已知常染色体隐性遗传的NSHI致病基因, 选用其侧翼的微卫星标记进行连锁分析, 发现该家系的致病基因与D13S175连锁。对GJB2基因进行整个编码区域的测序, 发现235碱基处发生了碱基C的纯合缺失, 这一突变可能是该家系中绝大多数患者致病的遗传基础。     

基于全基因组测序的MutMap方法在正向遗传学研究中的应用

在传统的正向遗传学分析过程中,基因定位需要构建复杂的后代群体,并借助大量分子标记进行遗传连锁分析和区间定位,使得这一过程成本高且耗时长。MutMap是近年来发展的基于高通量第二代测序技术的一种新的正向遗传学分析方法。该方法的优点是遗传定位的周期短且效率高。在此基础上扩展的新方法也不断出现,如基于自交的MutMap+、用于识别基因组缺失区间变异的MutMap-Gap、以及用于定位数量性状基因座的分析思路与MutMap类似的QTL-seq方法等。这些方法不需要建立繁琐的定位群体,甚至不依赖于遗传杂交和任何连锁信息即可进行,加快了对感兴趣表型的变异位点所在基因组区域的识别过程。本文对MutMap及其扩展方法进行了介绍,并对它们未来的应用和发展前景进行了讨论,以期为基于第二代测序技术的正向遗传学基因定位和作物遗传改良研究提供参考。     

甘蓝型油菜花瓣缺失基因的图谱定位

在无花瓣品系APT02和正常有花瓣品种中双4号构建的的F2分离群体中,运用AFLP和SRAP两种标记技术对甘蓝型油菜花瓣缺失基因进行分子标记和图谱定位。在两亲本间筛选20对AFLP引物和170对SRAP 引物,进一步通过BSA法筛选,获得了与甘蓝型油菜花瓣缺失基因WHB连锁的1个SRAP标记e8m3_4（600bp）和1个AFLP标记E3247_15（150bp）,标记与基因WHB之间的遗传距离分别为5 cM和13.5cM;构建了一个甘蓝型油菜(Brassica napus.L )的分子标记遗传连锁图谱,该图谱共包含213个AFLP标记、56个SRAP标记和1个形态标记,分布于17个主要连锁群、两个三联体和4个连锁对中,遗传图距总长2487.1cM,标记间平均距离为10.09 cM。通过图谱定位,控制花瓣缺失性状的基因WHB被定位到第4连锁群(LG4)上。     

关联分析及其在植物中的应用

关联分析是新近开始在植物数量性状研究和植物育种中应用的一种分析方法.它以连锁不平衡为基础鉴定某一群体内性状与遗传标记或候选基因间的关系,是对分子育种中QTL分析的补充和提高.本文在介绍连锁不平衡的定义和度量方法的基础上,讨论连锁不平衡程度和群体结构对关联分析的影响,综述了关联分析在植物方面的研究进展,并最后讨论了关联分析在植物数量性状和分子育种研究中可能的应用.     

中国植物遗传连锁图谱构建研究进展

遗传连锁图谱构建是基因组研究中的重要环节,是基因定位与克隆乃至基因组结构与功能研究的基础上。近十几年来,分子生物学特别是分子标记技术的飞速发展,为构建高饱和的植物遗传连锁图谱和利用分子标记进行辅助育种奠定了基础。综述了我国在植物遗传连锁图谱构建研究方面的进展及发展动态,列举了我国利用DNA分子标记构建的34张植物遗传连锁图谱实例,且讨论了当前我国在该领域研究中存在的问题并提出了解决途径。     

普通菜豆基因组学及抗炭疽病遗传研究进展

普通菜豆是重要的食用豆类之一,在世界各大洲普遍种植。近年来,普通菜豆在遗传图谱构建、新标记开发与利用、抗性基因定位以及比较基因组学等方面取得了很大进展。遗传连锁图谱的构建是基因定位与克隆的基础,是遗传研究中的重要内容;利用分子连锁图谱鉴定、标记和定位抗病基因将在种质改良和分子标记辅助育种方面发挥重要作用。豆科植物比较基因组学的研究成果为菜豆遗传连锁图谱的发展提供了新的思路。本文从普通菜豆遗传连锁图谱的获得、普通菜豆与大豆同线性比较以及抗炭疽病基因定位等方面进行了综述,以期为普通菜豆遗传改良和抗病育种提供参考。 关键词：普通菜豆;遗传连锁图;同线性比较;抗菜豆炭疽病     

梨遗传连锁图谱的构建及其与苹果图谱的比较

以‘丰水’为母本、‘砀山酥梨’为父本杂交所得的F1代104株单体为作图群体,利用SSR分子标记进行遗传连锁分析,应用Jionmap 3.0作图软件,构建了一张包含104个SSR分子标记,分属于18个连锁群的梨遗传连锁图谱,覆盖梨基因组总长831.8cM,平均图距为8.0cM。根据定位到该图谱上的SSR标记与苹果‘Fiesta’图谱进行比较,25个共有的SSR标记将该图谱和苹果图谱各连锁群连接起来,这些标记不仅呈现良好的共线性而且它们之间的相对遗传距离也很相近。研究认为,SSR标记作为锚定引物,可以与不同物种的遗传图谱相比较整合,为不同物种之间遗传信息的转移提供参考依据;同时该研究为梨树相关性状的基因定位、分离以及克隆奠定了基础。     

大粒裸燕麦(Avena nuda L.)遗传连锁图谱的构建

以“元莜麦”和“555”杂交得到的281个F2单株为作图群体,利用20对AFLP引物、3对SSR引物和1个穗型性状构建了一张大粒裸燕麦遗传连锁图。该图谱全长1544.8cM,包含19个连锁群,其上分布有92个AFLP标记、3个SSR标记和1个穗型形态标记,不同连锁群标记数为2-14个,长度在23.7-276.3cM之间,平均长度为81.3cM,标记间平均距离为20.1cM。穗型标记分离比符合3：1,11个AFLP标记表现为偏分离,偏分离比为11.5%。该图谱符合遗传连锁框架图的要求,为今后大粒裸燕麦的QTL定位、分子标记辅助育种和比较基因组学等研究奠定基础。     

X-连锁隐性遗传鱼鳞病的基因检测

问：我是一名女孩，我家系中有一个舅舅和我亲弟弟患病，已初步诊断为X-连锁隐性遗传鱼鳞病，在某医院做了大片断缺失型基因检测，但未检测到缺失。请问如何判断我是否也携带了致病基因？     

Clinical Application of an Innovative Multiplex-Fluorescent-Labeled STRs Assay for Prader-Willi Syndrome and Angelman Syndrome

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are two clinically distinct neurodevelopmental disorders caused by absence of paternally or maternally expressed imprinted genes on chr15q11.2-q13.3. Three mechanisms are known to be involved in the pathogenesis: microdeletions, uniparental disomy (UPD) and imprinting defects. Both disorders are difficult to be definitely diagnosed at early age if no available molecular cytogenetic tests. In this study, we identified 5 AS patients with the maternal deletion and 26 PWS patients with paternal deletion on chr15q11-q13 by using an innovative multiplex-fluorescent-labeled short tandem repeats (STRs) assay based on linkage analysis, and validated by the methylation-specific PCR and array comparative genomic hybridization techniques. More interesting, one of these PWS patients was confirmed as maternal uniparental isodisomy by the STR linkage analysis. The phenotypic and genotypic characteristics of these individuals were also presented. Our results indicate that the new linkage analysis is much faster and easier for large-scale screening deletion and uniparental disomy, thus providing a valuable method for early diagnosis of PWS/AS patients, which is critical for genetic diagnosis, management and improvement of prognosis.     

A modified MS-PCR approach to diagnose patients with Prader-Willi and Angelman syndrome

Prader-Willi (PWS) and Angelman (AS) syndromes are clinically distinct neurodevelopmental genetic diseases with multiple phenotypic manifestations. They are one of the most common genetic syndromes caused by non-Mendelian inheritance in the form of genomic imprinting, and can be attributable to the loss of gene expression due to imprinting within the chromosomal region 15q11-q13. Clinical diagnosis of PWS and AS is challenging, and the use of molecular and cytomolecular studies is recommended to help in determining the diagnosis of these conditions. The methylation analysis is a sensible approach; however there are several techniques for this purpose, such as the methylation-sensitive polymerase chain reaction (MS-PCR). This study aims to optimize the MS-PCR assay for the diagnosis of potential PWS and AS patients using DNA modified by sodium bisulfite. We used the MS-PCR technique of PCR described by Kosaki et al. (1997) adapted with betaine. All different concentrations of betaine used to amplify the methylated and unmethylated chromosomal region 15q11-q13 on the gene SNRPN showed amplification results, which increased proportionally to the concentration of betaine. The methylation analysis is a technically robust and reproducible screening method for PWS and AS. The MS-PCR assures a faster, cheaper and more efficient method for the primary diagnosis of the SNRPN gene in cases with PWS and AS, and may detect all of the three associated genetic abnormalities: deletion, uniparental disomy or imprinting errors.     

Combined cytogenetic and molecular analyses for the diagnosis of Prader-Willi/Angelman syndromes

Prader-Willi (PWS) and Angelman (AS) are syndromes of developmental impairment that result from the loss of expression of imprinted genes in the paternal (PWS) or maternal (AS) 15q11-q13 chromosome. Diagnosis on a clinical basis is difficult in newborns and young infants; thus, a suitable molecular test capable of revealing chromosomal abnormalities is required. We used a variety of cytogenetic and molecular approaches, such as, chromosome G banding, fluorescent in situ hybridization, a DNA methylation test, and a set of chromosome 15 DNA polymorphisms to characterize a cohort of 27 PWS patients and 24 suspected AS patients. Molecular analysis enabled the reliable diagnosis of 14 PWS and 7 AS patients, and their classification into four groups: (A) 6 of these 14 PWS subjects (44 %) had deletions of paternal 15q11-q13; (B) 4 of the 7 AS patients had deletions of maternal 15q11-q13; (C) one PWS patient (8 %) had a maternal uniparental disomy (UPD) of chromosome 15; (D) the remaining reliably diagnoses of 7 PWS and 3 AS cases showed abnormal methylation patterns of 15q11-q13 chromosome, but none of the alterations shown by the above groups, although they may have harbored deletions undetected by the markers used. This study highlights the importance of using a combination of cytogenetic and molecular tests for a reliable diagnosis of PWS or AS, and for the identification of genetic alterations.     

A DNA methylation imprint, determined by the sex of the parent, distinguishes the angelman and Prader-Willi syndromes

The Angelman (AS) and Prader-Willi (PWS) syndromes are two clinically distinct disorders that are caused by a differential parental origin of chromosome 15q11-q13 deletions. Both also can result from uniparental disomy (the inheritance of both copies of chromosome 15 from only one parent). Loss of the paternal copy of 15q11-q13, whether by deletion or maternal uniparental disomy, leads to PWS, whereas a maternal deletion or paternal uniparental disomy leads to AS. The differential modification in expression of certain mammalian genes dependent upon parental origin is known as genomic imprinting, and AS and PWS represent the best examples of this phenomenon in humans. Although the molecular mechanisms of genomic imprinting are unknown, DNA methylation has been postulated to play a role in the imprinting process. Using restriction digests with the methyl-sensitive enzymes HpaII and HhaI and probing Southern blots with several genomic and cDNA probes, we have systematically scanned segments of 15q11-q13 for DNA methylation differences between patients with PWS (20 deletion, 20 uniparental disomy) and those with AS (26 deletion, 1 uniparental disomy). The highly evolutionarily conserved cDNA, DN34, identifies distinct differences in DNA methylation of the parental alleles at the D15S9 locus. Thus, DNA methylation may be used as a reliable, postnatal diagnostic tool in these syndromes. Furthermore, our findings demonstrate the first known epigenetic event, dependent on the sex of the parent, for a locus within 15q11-q13. We propose that expression of the gene detected by DN34 is regulated by genomic imprinting and, therefore, that it is a candidate gene for PWS and/or AS.     

Prader-Willi syndrome with an unusually large 15q deletion due to an unbalanced translocation t(4;15)

Prader-Willi syndrome (PWS) is a neurobehavioral disorder caused by deletions in the 15q11-q13 region, by maternal uniparental disomy of chromosome 15 or by imprinting defects. Structural rearrangements of chromosome 15 have been described in about 5% of the patients with typical or atypical PWS phenotype. An 8-year-old boy with a clinical diagnosis of PWS, severe neurodevelopmental delay, absence of speech and mental retardation was studied by cytogenetic and molecular techniques, and an unbalanced de novo karyotype 45,XY,der(4)t(4;15)(q35;q14),-15 was detected after GTG-banding. The patient was diagnosed by SNURF-SNRPN exon 1 methylation assay, and the extent of the deletions on chromosomes 4 and 15 was investigated by microsatellite analysis of markers located in 4qter and 15q13-q14 regions. The deletion of chromosome 4q was distal to D4S1652, and that of chromosome 15 was located between D15S1043 and D15S1010. Our patient's severely affected phenotype could be due to the extent of the deletion, larger than usually seen in PWS patients, although the unbalance of the derivative chromosome 4 cannot be ruled out as another possible cause. The breakpoint was located in the subtelomeric region, very close to the telomere, a region that has been described as having the lowest gene concentrations in the human genome.     

Prader-Willi syndrome: clinical genetics, cytogenetics and molecular biology

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder that arises from lack of expression of paternally inherited genes known to be imprinted and located in the chromosome 15q11-q13 region. PWS is considered the most common syndromal cause of life-threatening obesity and is estimated at 1 in 10,000 to 20,000 individuals. A de novo paternally derived chromosome 15q11-q13 deletion is the cause of PWS in about 70% of cases, and maternal disomy 15 accounts for about 25% of cases. The remaining cases of PWS result either from genomic imprinting defects (microdeletions or epimutations) of the imprinting centre in the 15q11-q13 region or from chromosome 15 translocations. Here, we describe the clinical presentation of PWS, review the current understanding of causative cytogenetic and molecular genetic mechanisms, and discuss future directions for research.     

A combination of five short tandem repeats of chromosome 15 significantly improves the identification of Prader-Willi syndrome etiology in the Argentinean population

Prader-Willi syndrome (PWS) is a multisystemic disorder caused by the loss of expression of paternally transcribed genes in the PWS critical region of chromosome 15. Various molecular mechanisms are known to lead to PWS: deletion 15q11-q13 (75% of cases), maternal uniparental disomy (matUPD15) (23%) and imprinting defects (2%). FISH and microsatellite analysis are required to establish the molecular etiology, which is essential for appropriate genetic counseling and care management. We characterized an Argentinean population, using five microsatellite markers (D15S1035, D15S11, D15S113, GABRB3, D15S211) chosen to develop an appropriate cost-effective method to establish the parental origin of chromosome 15 in nondeleted PWS patients. The range of heterozygosity for these five microsatellites was 0.59 to 0.94. The average heterozygosity obtained for joint loci was 0.81. The parental origin of chromosome 15 was established by microsatellite analysis in 19 of 21 non-deleted PWS children. We also examined the origin of the matUPD15; as expected, most of disomies were due to a maternal meiosis I error. The molecular characterization of this set of five microsatellites with high heterozygosity and polymorphism information content improves the diagnostic algorithm of Argentinean PWS children, contributing significantly to adequate genetic counseling of such families.     

Molecular, cytogenetic, and clinical investigations of Prader-Willi syndrome patients.

Thirty-seven patients presenting features of the Prader-Willi syndrome (PWS) have been examined using cytogenetic and molecular techniques. Clinical evaluation showed that 29 of these patients fulfilled diagnostic criteria for PWS. A deletion of the 15q11.2-q12 region could be identified molecularly in 21 of these cases, including several cases where the cytogenetics results were inconclusive. One clinically typical patient is deleted at only two of five loci normally included in a PWS deletion. A patient carrying a de novo 13;X translocation was not deleted for the molecular markers tested but was clinically considered to be "atypical" PWS. In addition, five cases of maternal heterodisomy and two of isodisomy for 15q11-q13 were observed. All of the eight patients who did not fulfill clinical diagnosis of PWS showed normal maternal and paternal inheritance of chromosome 15 markers; however, one of these carried a ring-15 chromosome. A comparison of clinical features between deletion patients and disomy patients shows no significant differences between the two groups. The parental ages at birth of disomic patients were significantly higher than those for deletion patients. As all typical PWS cases showed either a deletion or disomy of 15q11.2-q12, molecular examination should provide a reliable diagnostic tool. As the disomy patients do not show either any additional or more severe features than typical deletion patients do, it is likely that there is only one imprinted region on chromosome 15 (within 15q11.2-q12).     

Molecular diagnosis of the Prader-Willi and Angelman syndromes by detection of parent-of-origin specific DNA methylation in 15q11-13

The Prader-Willi syndrome (PWS) and the Angelman syndrome (AS) are distinct genetic disorders that are caused by a deletion of chromosome region 15q11-13 or by uniparental disomy for chromosome 15. Whereas PWS results from the absence of a paternal copy of 15q11-13, the absence of a maternal copy of 15q11-13 leads to AS. We have found that an MspI/HpaII restriction site at the D15S63 locus in 15q11-13 is methylated on the maternally derived chromosome, but unmethylated on the paternally derived chromosome. Based on this difference, we have devised a rapid diagnostic test for patients suspected of having PWS and AS.     

A molecular and cytogenetic study in Finnish Prader-Willi patients

The Prader-Willi syndrome (PWS) is a developmental disorder caused by a deficiency of paternal contributions, arising from differently sized deletions, uniparental disomy or rare imprinting mutations, in the chromosome region 15q11–q13. We studied 41 patients with suspected PWS and their parents using cytogenetic and molecular techniques. Of the 27 clinically typical PWS patients, 23 (85%) had a molecular deletion that could be classified into four size categories. Only 15 of them (71%) could be detected cytogenetically. Maternal uniparental heterodisomy was observed in four cases. The rest of the patients showed no molecular defects including rare imprinting mutations. In our experience, the use of the methylation test with the probe PW71 (D15S63), together with the probe hN4HS (SNRPN), which distinguishes between a deletion and uniparental disomy, is the method of choice for the diagnosis of PWS.