一个先天性手足裂畸形家系的遗传学分析

目的对1个先天性手足裂畸形家系进行遗传学分析,以鉴定致病性变异。方法提取先证者及家系中其他患者的基因组DNA,应用染色体微阵列技术对患者进行全基因组拷贝数变异分析。结果染色体微阵列分析显示先证者和另外3例患者存在染色体10q24.31-q24.32区域约400 kb的片段重复变异,该重复区域包含完整的LBX1、BTRC、POLL及DPCD基因,并含有FBXW4基因的部分外显子。结论染色体10q24.31-q24.32区域的重复与该家系患者疾病表型共分离,基因组拷贝数变异为患者的致病原因。     

一个染色体14q微缺失的遗传学分析

目的分析1例自闭症、智力低下和癫痫患儿的遗传学病因。方法应用常规G显带染色体核型分析、单核昔酸多态性微阵列(single nucleotide polymorphism array,SNP array)技术检测染色体变异,用高通量测序筛选致病变异位点,Sanger测序验证,查阅数据库及文献分析,以明确缺失区及致病变异基因的病理意义。结果患儿及其父母外周血G显带核型分析结果均未见异常。SNP array检测发现患儿染色体14 qll.2区存在460 kb的缺失,高通量及Sanger测序显示患儿携带NALCN基因新发变异,患儿及其母亲COL4A5基因发生半合子变异。结论染色体14qll.2微缺失与NALCN变异可能与患儿自闭症、智力低下及癫痫等表型相关。     

用高分辨率微阵列比较基因组杂交分析一个孤独症家系的新生拷贝数变异

目的 对1个孤独症家系进行新发拷贝数变异(copy number variations,CNV)分析.方法 应用高分辨率全基因组芯片(Affymetrix Cytogenetics Whole-Genome 2.7M Array)检测该家系4名成员的基因组拷贝数,用Affymetrix Chromosome Analysis Suite软件分析结果.以基因组变异数据库亚洲正常人群及先证者父母、同胞为对照,分析先证者的新发CNV.结果 先证者存在89个新发拷贝数变异,其中5号、11号和14号染色体新发CNV总长占染色体全长超过1‰.3p26.1、4q22.2、5p15.2等区域也存在新发CNV,涉及GRM7、GRID2、CTNND2等10个与神经系统发育相关基因.结论 先证者多个与神经系统发育相关的基因存在新发拷贝数变异,这为探索孤独症的发病机理提供了新的线索.高分辨率基因组CNV芯片能够快速、准确地检测基因组的微小失衡,在遗传病诊断方面具有广阔的应用前景.     

1个先天性白内障家系的致病基因鉴定及遗传学分析

目的 对1个先天性白内障家系进行表型和基因分析,鉴别其致病基因,分析基因与家系异常表型的关系,为该家系的遗传咨询、诊断及治疗提供参考。方法 采集该家系成员的临床资料,诊断其白内障表型、绘制家系图、分析遗传方式。提取家系成员的外周血DNA,利用外显子组测序在先证者的基因组中寻找致病变异位点,利用多重连接依赖探针扩增技术筛查大片段缺失/插入;排除编码区变异、大片段缺失/插入与该家系的关系后,采用全基因组测序筛查该家系致病基因。结果 该家系22位成员参与临床检查,其中13人被诊断患有白内障,主要表现为眼部皮质混浊、核混浊、眼底窥不清等,年龄最大84岁,最小11岁。外显子组测序所得候选变异位点为COL7A1 c.6727T>C,但该变异在家系内未与疾病表型共分离;MLPA检测结果显示该家系在RHO、RP1、IMPDH1、PRPF31等4个基因不存在大片段缺失或重复;全基因组测序发现铁蛋白轻链亚基编码基因（FTL）5’-UTR区c.-168G>C(rs398124635)杂合变异,Sanger测序证明该变异位点在家系中与疾病表型共分离,Clinvar数据库评估该变异为有害变异。结论 ...     

一例产前诊断Wolf-Hirschhorn综合征胎儿的遗传学分析

目的探讨产前诊断一例Wolf-Hirschhorn综合征(WHS)胎儿的确诊及预后。方法运用BoBs(BACs-on-Beads)技术与染色体G显带核型分析发现胎儿4号染色体短臂存在缺失,后续应用Affymetrix CytoScan 750K Array芯片技术检测其染色体拷贝数变异。结果 BoBs结果提示胎儿染色体4p16探针拷贝数缺失,核型分析结果46,XY,del(4)(p15.3),基因芯片检测证实其在4号染色体4p16.3p15.32区段存在17.1Mb片段的缺失,内含FGFR3,LETM1,WHSC1,NELFA等90个OMIM基因,累及上述基因的4p16.3区段的缺失与Wolf-Hirschhorn综合征疾病相关。结论 BoBs,G显带核型分析和全基因组基因芯片检测结果一致。当常规核型分析不能精确确定染色体缺失片段大小时,联合基因芯片技术可以确定染色体的拷贝数变异及其累及的致病基因,为遗传咨询提供临床诊断及预后的依据。     

实时定量PCR在强直性肌营养不良1型重复突变检测中的应用

目的 鉴定一个强直性肌营养不良(dystrophy myotonica,DM)家系的致病突变,探讨实时定量PCR能否用于检测导致DM1的CTG重复延展突变.方法 采集家系成员外周血,提取基因组DNA.针对DM1位点DMPK基因内的CTG重复区和DM2位点CNBP基因内的CCTG重复区进行普通PCR、实时荧光定量PCR、微卫星标记连锁分析.结果 CTG重复区普通PCR产物电泳显示患者特有大于2 kb的弥散带.定量PCR显示,患者CTG重复区相对拷贝数约为0.5,CCTG重复区相对拷贝数约为1.在DM1位点的微卫星标记,患者均有共享等位基因;而在DM2位点的大部分标记,患者没有共享等位基因.结论 此DM家系的致病突变是DM1位点的CTG重复延展突变;应用实时定量PCR可以确定高度重复延展片段扩增失败,从而推断重复延展突变的存在,达到快速检测DM1的目的.     

实时定量PCR在强直性肌营养不良1型重复突变检测中的应用

目的 鉴定一个强直性肌营养不良(dystrophy myotonica,DM)家系的致病突变,探讨实时定量PCR能否用于检测导致DM1的CTG重复延展突变.方法 采集家系成员外周血,提取基因组DNA.针对DM1位点DMPK基因内的CTG重复区和DM2位点CNBP基因内的CCTG重复区进行普通PCR、实时荧光定量PCR、微卫星标记连锁分析.结果 CTG重复区普通PCR产物电泳显示患者特有大于2 kb的弥散带.定量PCR显示,患者CTG重复区相对拷贝数约为0.5,CCTG重复区相对拷贝数约为1.在DM1位点的微卫星标记,患者均有共享等位基因;而在DM2位点的大部分标记,患者没有共享等位基因.结论 此DM家系的致病突变是DM1位点的CTG重复延展突变;应用实时定量PCR可以确定高度重复延展片段扩增失败,从而推断重复延展突变的存在,达到快速检测DM1的目的.     

实时定量PCR在强直性肌营养不良1型重复突变检测中的应用

目的 鉴定一个强直性肌营养不良(dystrophy myotonica,DM)家系的致病突变,探讨实时定量PCR能否用于检测导致DM1的CTG重复延展突变.方法 采集家系成员外周血,提取基因组DNA.针对DM1位点DMPK基因内的CTG重复区和DM2位点CNBP基因内的CCTG重复区进行普通PCR、实时荧光定量PCR、微卫星标记连锁分析.结果 CTG重复区普通PCR产物电泳显示患者特有大于2 kb的弥散带.定量PCR显示,患者CTG重复区相对拷贝数约为0.5,CCTG重复区相对拷贝数约为1.在DM1位点的微卫星标记,患者均有共享等位基因;而在DM2位点的大部分标记,患者没有共享等位基因.结论 此DM家系的致病突变是DM1位点的CTG重复延展突变;应用实时定量PCR可以确定高度重复延展片段扩增失败,从而推断重复延展突变的存在,达到快速检测DM1的目的.     

中国人及高加索人群P20探针MSPI位点多态性差异

本文应用抗肌萎缩蛋白基因内P2o（DXS269）探针对中国人和高加索人MspI位点进行限制性片段长度多态性（RFLP）分析，发现高加索人的杂交日上除了出现文献报告的多态性住点M1外。尚存在中国人杂交图上M2的1.9kb片段，且为高加索人的常有片段，同时存在与中国人相同的常有片段－小于1.okb（约o.3kb）的片段、此结果表明中国人和高加索人群在P2o区域经MspI酶切后的片段长度差异是MSPI识别位点的多态性。     

三例Mowat-Wilson综合征患儿的临床特征及基因分析

目的探讨3例伴有特殊面容的智力障碍/发育迟缓患儿的遗传学特征。方法采集患儿的外周血样, 分别进行G显带染色体核型分析和染色体微阵列分析(chromosomal microarray analysis, CMA), 并对患儿3进行全外显子组测序(whole exome sequencing, WES)。结果 3例患儿的染色体核型均未见异常。CMA检测患儿1为arr[GRCh37]:2q22.3(145 128 071-145 159 029)×1, 存在大约31 kb的缺失, 为致病性拷贝数变异, 涉及ZEB2基因第8 ～ 10外显子;患儿2为arr[hg19]:2q22.3(145 071 457-146 881 759)×1, 存在1.81 Mb的缺失, 涉及ZEB2和GTDC1基因;患儿3为arr[GRCh37]:9p23p23(11 698 261-12 106 261)×1, 存在408 kb的缺失, 未涉及相关基因。WES结果显示其ZEB2基因第8外显子存在c.2102C>A(p.Ser701*)的无义变异, 该变异已被ClinVar数据库收录, 评级为致病性, San...     

Targeted genome screen of panic disorder and anxiety disorder proneness using homology to murine QTL regions

Family and twin studies have indicated that genes influence susceptibility to panic and phobic anxiety disorders, but the location of the genes involved remains unknown. Animal models can simplify gene-mapping efforts by overcoming problems that complicate human pedigree studies including genetic heterogeneity and high phenocopy rates. Homology between rodent and human genomes can be exploited to map human genes underlying complex traits. We used regions identified by quantitative trait locus (QTL)-mapping of anxiety phenotypes in mice to guide a linkage analysis of a large multiplex pedigree (99 members, 75 genotyped) segregating panic disorder/agoraphobia. Two phenotypes were studied: panic disorder/agoraphobia and a phenotype ("D-type") designed to capture early-onset susceptibility to anxiety disorders. A total of 99 markers across 11 chromosomal regions were typed. Parametric lod score analysis provided suggestive evidence of linkage (lod = 2.38) to a locus on chromosome 10q under a dominant model with reduced penetrance for the anxiety-proneness (D-type) phenotype. Nonparametric (NPL) analysis provided evidence of linkage for panic disorder/agoraphobia to a locus on chromosome 12q13 (NPL = 4.96, P = 0.006). Modest evidence of linkage by NPL analysis was also found for the D-type phenotype to a region of chromosome 1q (peak NPL = 2.05, P = 0.035). While these linkage results are merely suggestive, this study illustrates the potential advantages of using mouse gene-mapping results and exploring alternative phenotype definitions in linkage studies of anxiety disorder.     

Familial Prader-Willi syndrome: case report and a literature review

Prader-Willi syndrome (PWS) is a neurobehavioural disorder arising through a number of different genetic mechanisms. All involve loss of paternal gene expression from chromosome 15q11q13. Although the majority of cases of PWS are sporadic, precise elucidation of the causative genetic mechanism is essential for accurate genetic counselling as the recurrence risk varies according to the mechanism involved. A pair of siblings affected by PWS is described. Neither demonstrates a microscopically visible deletion in 15q11q13 or maternal disomy. Methylation studies at D15S63 and at the SNRPN locus confirm the diagnosis of PWS. Molecular studies reveal biparental inheritance in both siblings with the exception of D15S128 and D15S63 where no paternal contribution is present indicating a deletion of the imprinting centre. Family studies indicate that the father of the siblings carries the deletion which, he has inherited from his mother. The recurrence risk for PWS in his offspring is 50%.     

Evidence of susceptibility loci on 4q32 and 16p12 for bipolar disorder

We performed a genome-wide scan for susceptibility loci in bipolar disorder in a study sample colleted from the isolated Finnish population, consisting of 41 families with at least two affected siblings. We identified one distinct locus on 16p12 providing significant evidence for linkage in two-point analysis (Z(max)=3.4). Furthermore, three loci with a two-point LOD score >2.0 were observed with markers on 4q32, 12q23 and Xq25, the latter locus having been earlier identified in one extended Finnish pedigree. In the second stage we fine mapped these chromosomal regions and also genotyped additional family members. In the fine mapping stage, 4q32 provided significant evidence of linkage for the three-point analyses (Z(max)=3.6) and 16p12 produced a three-point LOD score of 2.7. Since the identified chromosomal regions replicate earlier linkage findings in either bipolar disorder or other mental disorders, they should be considered good targets for further genetic analyses.     

Cognitive abilities in siblings of children with autism spectrum disorders

The aim of the present study was to assess the cognitive profiles of children with autistic spectrum disorder and of their healthy siblings (Siblings). With the term cognitive profile, we indicate the relationship extant among the values of verbal and performance subtests of the Wechsler Intelligence Scale. The conducted statistical analyses indicated that, although siblings showed a normal intelligent quotient and did not differ in this aspect from typically developing group, their cognitive profile was amazingly similar to that of their relatives affected by autism. A k-means clustering analysis on the values of single subtests further confirmed this result, showing a clear separation between typically developing children on the one side, and autistics and their siblings on the other. We suggest that the common cognitive profile observed in autistic children and their siblings could represent a marker of liability to autism and, thus, a possible intermediate phenotype of this syndrome.     

Large duplication in LMBR1 gene in a large Chinese pedigree with triphalangeal thumb polysyndactyly syndrome

Polydactyly and syndactyly are digital abnormalities in limb‐associated birth defects usually caused by genetic disorders. In this study, a five‐generation Chinese pedigree was found with triphalangeal thumb polysyndactyly syndrome (TPTPS), showing an autosomal dominant pattern of inheritance. We utilized linkage analysis and whole genome sequencing (WGS) for the genetic diagnosis of this pedigree. Linkage analysis was performed using a genome‐wide single nucleotide polymorphism (SNP) chip and three genomic regions were identified in chromosomes 2, 6, and 7 with significant linkage signals. WGS discovered a copy number variation (CNV) mutation caused by a large duplication region at the tail of chromosome 7 located in exons 1–5 of the LMBR1 gene, including the zone of polarizing activity regulatory sequence (ZRS), with a length of approximately 180 kb. A real‐time polymerase chain reaction (PCR) assay confirmed the duplication. The findings of our study supported the notion that large duplications including the ZRS caused TPTPS. Our study showed that linkage analysis in combination with WGS could successfully identify the disease locus and causative mutation in TPTPS, which could help elucidate the molecular mechanisms and genotype–phenotype correlations in polydactyly.     

Genetically determined low maternal serum dopamine beta-hydroxylase levels and the etiology of autism spectrum disorders

Autism, a neurodevelopmental disability characterized by repetitive stereopathies and deficits in reciprocal social interaction and communication, has a strong genetic basis. Since previous findings showed that some families with autistic children have a low level of serum dopamine beta-hydroxylase (DbetaH), which catalyzes the conversion of dopamine to norepinephrine, we examined the DBH gene as a candidate locus in families with two or more children with autism spectrum disorder using the affected sib-pair method. DBH alleles are defined by a polymorphic AC repeat and the presence/absence (DBH+/DBH-) of a 19-bp sequence 118 bp downstream in the 5' flanking region of the gene. There was no increased concordance for DBH alleles in affected siblings, but the mothers had a higher frequency of alleles containing the 19-bp deletion (DBH-), compared to an ethnically similar Canadian comparison group (chi(2) = 4.20, df = 1, P = 0.02 for all multiplex mothers; chi(2) = 4.71, df = 1, P < 0.02 for mothers with only affected sons). Although the odds ratios suggested only a moderate relevance for the DBH- allele as a risk allele, the attributable risk was high (42%), indicating that this allele is an important factor in determining the risk for having a child with autism. DBH genotypes also differed significantly among mothers and controls, with 37% of mothers with two affected sons having two DBH- alleles, compared to 19% of controls (chi(2) = 5.81, df = 2, P = 0.03). DbetaH enzyme activity was lower in mothers of autistic children than in controls (mean was 23.20 +/- 15.35 iU/liter for mothers vs. 33.14 +/- 21.39 iU/liter for controls; t = - 1.749, df = 46, P = 0.044). The DBH- allele was associated with lower mean serum DbetaH enzyme activity (nondeletion homozygotes: 41.02 +/- 24.34 iU/liter; heterozygotes: 32.07 +/- 18.10 iU/liter; and deletion homozygotes: 22.31 +/- 13.48 iU/liter; F = 5.217, df = 2, P = 0.007) in a pooled sample of mothers and controls. Taken together, these findings suggest that lowered maternal serum DbetaH activity results in a suboptimal uterine environment (decreased norepinephrine relative to dopamine), which, in conjunction with genotypic susceptibility of the fetus, results in autism spectrum disorder in some families.     

Bootstrapping in human genetic linkage

Linkage analysis of discrete Mendelian traits has made a major contribution to the mapping of the human genome. However, in more complex situations, particularly Mendelian disorders showing locus heterogeneity, linkage results have sometimes been misleading. The bootstrap confidence interval provides an assessment of the goodness of fit of the data to the genetic model and the presence of heterogeneity can inflate the confidence interval indicating that the fit is poor. The loss in statistical power and the potential unreliability of linkage analyses based on small samples or subsamples of pedigree material is explored and illustrated by using simulated data and also real data on 37 families affected by the heterogeneous disorder, tuberous sclerosis.     

Three siblings with Prader–Willi syndrome caused by imprinting center microdeletions and review

Prader–Willi syndrome (PWS) is a complex genetic imprinting disorder characterized by childhood obesity, short stature, hypogonadism/hypogenitalism, hypotonia, cognitive impairment, and behavioral problems. Usually PWS occurs sporadically due to the loss of paternally expressed genes on chromosome 15 with the majority of individuals having the 15q11‐q13 region deleted. Examples of familial PWS have been reported but rarely. To date 13 families have been reported with more than one child with PWS and without a 15q11‐q13 deletion secondary to a chromosome 15 translocation, inversion, or uniparental maternal disomy 15. Ten of those 13 families were shown to carry microdeletions in the PWS imprinting center. The microdeletions were found to be of paternal origin in nine of the ten cases in which family studies were carried out. Using a variety of techniques, the microdeletions were identified in regions within the complex SNRPN gene locus encompassing the PWS imprinting center. Here, we report the clinical and genetic findings in three adult siblings with PWS caused by a microdeletion in the chromosome 15 imprinting center inherited from an unaffected father that controls the activity of genes in the 15q11‐q13 region and summarize the 13 reported cases in the literature.

     

Hemizygous deletions on chromosome 1p21.3 involving the DPYD gene in individuals with autism spectrum disorder

We describe the identification and clinical presentation of four individuals from three unrelated families with hemizygous deletions involving the DPYD gene at chromosome 1p21.3. DPYD encodes dihydropyrimidine dehydrogenase, which is the initial and rate-limiting enzyme in the catabolism of pyrimidine bases. All four individuals described met diagnostic criteria for autism spectrum disorder with severe speech delay. Patient 1's deletion was originally reported in 2008, and more detailed clinical information is provided. Subsequently, this male individual was found to have a missense mutation in the X-linked PTCHD1 autism susceptibility gene, which may also contribute to the phenotype. Patients 2 and 3 are siblings with a novel deletion encompassing the DPYD gene. In their mother, the genomic region deleted from chromosome 1p21.3 was inserted into chromosome 10. A fourth proband had a novel 10-kb intragenic deletion of exon 6 of the DPYD gene detected on a higher resolution microarray. Our study suggests that hemizygous deletions involving the DPYD locus present with variable phenotypes which can include speech delay and autistic features, and may also be influenced by additional mutations in other genes, issues which need to be considered in genetic counseling.     

Targeted genome screen of panic disorder and anxiety disorder proneness using homology to murine QTL regions*

Family and twin studies have indicated that genes influence susceptibility to panic and phobic anxiety disorders, but the location of the genes involved remains unknown. Animal models can simplify gene‐mapping efforts by overcoming problems that complicate human pedigree studies including genetic heterogeneity and high phenocopy rates. Homology between rodent and human genomes can be exploited to map human genes underlying complex traits. We used regions identified by quantitative trait locus (QTL)‐mapping of anxiety phenotypes in mice to guide a linkage analysis of a large multiplex pedigree (99 members, 75 genotyped) segregating panic disorder/agoraphobia. Two phenotypes were studied: panic disorder/agoraphobia and a phenotype (“D‐type”) designed to capture early‐onset susceptibility to anxiety disorders. A total of 99 markers across 11 chromosomal regions were typed. Parametric lod score analysis provided suggestive evidence of linkage (lod = 2.38) to a locus on chromosome 10q under a dominant model with reduced penetrance for the anxiety‐proneness (D‐type) phenotype. Nonparametric (NPL) analysis provided evidence of linkage for panic disorder/agoraphobia to a locus on chromosome 12q13 (NPL = 4.96, P = 0.006). Modest evidence of linkage by NPL analysis was also found for the D‐type phenotype to a region of chromosome 1q (peak NPL = 2.05, P = 0.035). While these linkage results are merely suggestive, this study illustrates the potential advantages of using mouse gene‐mapping results and exploring alternative phenotype definitions in linkage studies of anxiety disorder. © 2001 Wiley‐Liss, Inc.