应用单核苷酸多态性芯片检测7q部分缺失伴发育迟缓患儿一例

目的探讨1例生长发育迟缓患儿的遗传学原因,分析患儿基因组拷贝数变异(copy number variations,CNVs)及其所含基因与临床表型的对应关系。方法用常规G显带技术分析患儿及其父母的外周血染色体核型,用单核苷酸多态微阵列芯片技术(single nucleotide polymorphisms array,SNP-array)进行DNA拷贝数分析。结果患儿及其父母的外周血常规染色体核型分析均未见异常。SNP-array分析结果显示患儿染色体7q11.23区存在1.41 Mb杂合缺失,其缺失与Williams-Beuren综合征相关,父母双方均未见该缺失。结论患儿7号染色体长臂拷贝数变异所致的Williams-Beuren综合征与患儿的发育迟缓及特殊面容等临床表型相关,应用SNP-array技术在临床检测不明原因发育迟缓患儿中具有显著的优势。     

一例22部分三体综合征患儿的表型及遗传学研究

目的明确1例发育迟缓伴多发畸形患儿染色体拷贝数变异的性质和来源,分析其与表型的相关性。方法应用G显带染色体核型分析以及单核苷酸多态性微阵列芯片(single nucleotide polymorphism array,SNP array)技术对患儿及其父母进行检测。结果G显带分析提示患儿的染色体核型为46,X,add(Y)(q11.23),其父母核型均未见异常。SNP array检测提示患儿染色体22q12qter区存在21.6 Mb重复,其父母则未见染色体拷贝数异常。结论患儿染色体22q12qter区域微重复为新发突变,可能与其智力障碍、多发畸形等表型相关。     

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。     

一例主动脉狭窄伴拇指缺如患儿的遗传学诊断CSCD

目的分析1例主动脉狭窄伴拇指缺如患儿的发病机制,为遗传咨询提供依据。方法用常规G显带分析患儿及其父母的外周血染色体核型,用微阵列比较基因组杂交（array comparative genomic hybridization,aCGH）技术对患儿及其父母进行染色体片段重复／缺失的分析。结果G显带分析结果显示患儿及其父母染色体核型未见异常。aCGH检测结果显示患儿2q22．3-q23．3区存在5．86Mb的杂合缺失,其父母未检测到染色体微重复／微缺失。结论患儿2q22．3-q23．3缺失为新发突变,诊断为2q23．1微缺失综合征,MBD5基因可能是该综合征的关键基因。     

一例罕见的TCF4基因部分缺失型Pitt-Hopkins综合征的遗传学分析

目的探讨1例脑发育落后患儿的遗传学病因。方法采用常规G显带技术分析患儿及其双亲的染色体核型,应用单核苷酸多态性微阵列(single nucleotide polymorphism array,SNP-array)技术对患儿进行全基因组拷贝数变异(copy number variations,CNVs)筛查,并对其双亲进行验证。结果患儿及其双亲染色体G显带核型分析均未见异常。SNP-array检测双亲均未见异常,发现患儿染色体18q21.2区存在172 kb(52957042~53129237)的新发缺失,仅涉及OMIM基因TCF4,导致TCF4第6~8外显子的缺失。结论染色体18q21.2区的缺失与Pitt-Hopkins综合征密切相关。SNP-array检测为该患儿的确诊提供了依据。     

一例表现为主动脉瓣狭窄的非典型Williams-Beuren综合征患儿的遗传学诊断及分析

目的对1例主动脉瓣狭窄的患儿进行遗传学诊断,分析其发病机制。方法采用常规G显带染色体分析、微阵列比较基因组杂交(array comparative genomic hybridization,aCGH)及多重连接探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术分析患儿及其父母的染色体核型和基因组拷贝数变异。结果患儿及其父母的外周血染色体核型均未见异常。aCGH检测显示患儿7q11.23区存在278 kb杂合缺失,与Williams-Beuren综合征(Williams-Beuren syndrome,WBS)关键区部分重叠,涉及WBS的关键致病基因之一ELN。MLPA检测证实患儿存在上述缺失,患儿父母未发现染色体微重复/微缺失。结论患儿7q11.23区杂合缺失为新发突变。ELN基因单倍剂量不足可能是其发生主动脉瓣狭窄的原因,诊断为非典型WBS。     

7q部分重复患儿1例的表型及遗传学分析

目的明确1例不明原因生长发育迟缓患儿染色体异常的性质及来源, 分析其与表型的相关性。方法选择2019年7月9日就诊于郑州大学附属儿童医院的1例患儿作为研究对象。用G显带染色体核型分析及单核苷酸多态性微阵列芯片技术(SNP array)对患儿及其父母进行检测。结果 G显带核型分析结合SNP array技术提示患儿染色体核型为:46, XX, dup(7)(q34q36.3), 其父母核型均未见异常。SNP array检测提示患儿染色体7q34q36.3区存在20.6 Mb重复, 具体为arr[hg19]7q34q36.3(138335828₁58923941)×3, 其父母均未查见染色体拷贝数异常。结论患儿为罕见的7q部分重复且为新发变异, 其基因型与表型的相关性有助于临床诊疗及遗传咨询。     

疑似Prader-Willi综合征患儿的细胞遗传学和基因组拷贝数变异检测

目的 对1个疑似Prader-Willi综合征患儿进行基因组拷贝数变异检测,确诊其病因.方法 收集临床诊断疑似Prader-Willi综合征患儿及其父母外周血,常规G显带和高分辨染色体检查并提取患儿基因组DNA行全基因组拷贝数变异检测.结果 患儿及其父母高分辨染色体技术结果未见异常,但全基因组拷贝数检测患儿结果提示染色体15q11.2-13.1区域杂合缺失5 Mb;患儿定期做Baylay、Gesell发育量表检查提示智商为60～70分,符合Prader-Willi综合征的临床特征.结论 染色体15q11.2-13.1区域杂合缺失是该家系Prader-Willi综合征的病因.当Prader-Willi综合征患者在细胞遗传学未发现异常时,应进一步分子遗传学检查可弥补细胞遗传学方法的不足.     

一例18q21.2q21.32杂合缺失所致Pitt-Hopkins综合征患儿的遗传学分析

目的探讨1例全面发育迟滞伴智力障碍患儿的遗传学病因。方法采用染色体G显带核型分析、拷贝数变异测序(copy number variation sequencing, CNV-seq)以及染色体高分辨技术对患儿及其父母进行变异筛查, 并明确其亲代来源。结果患儿及其父亲的染色体核型均为46, XY, del(18)(q21.1q21.3), 母亲为46, XX。CNV-seq提示患儿为arr[19]18q21.2-q21.32(chr18:48 422 190-58 039 582)×1, 即存在约10.58 Mb缺失, 涉及TCF4基因, 而父母均未发现相同缺失。经染色体高分辨技术发现患儿父亲18号染色体长臂的部分片段(18q21.1q21.3)插入到了5号短臂(5p13.1)。结论染色体G显带核型分析与CNV-seq技术能有效诊断Pitt-Hopkins综合征, 染色体高分辨技术有助于明确染色体异常的亲代起源。     

一例合并6q21-q22．31微缺失的锁骨颅骨发育不良患者的遗传学分析CSCD

目的对1例发育迟缓伴多发畸形患儿进行遗传学检测,分析其预后及发生机制,为临床咨询提供依据。 方法采用常规G显带和微阵列比较基因组杂交（array comparative genomic hybridization, aCGH）技术分析患儿及其父母的外周血染色体核型和DNA。结果G显带分析结果显示,患儿染色体核型为46,XX,del（6）（q22）,inv（6）（p21.1q21）,其父母染色体核型未见异常。aCGH检测结果显示患儿6p21.1区存在800 kb杂合缺失,包含RUNX2基因,6q21-q22.31区存在11.79 Mb杂合缺失,其父母未检测到染色体微重复/微缺失。 结论患儿为染色体新发倒位,两处微缺失均为新发突变,具有致病性。6p21.1区域RUNX2基因微缺失导致锁骨颅骨发育不良,6q21-q22.31区域微缺失可能与患儿脑部结构发育异常相关。     

Concurrent de novo ZFHX4 variant and 16q24.1 deletion in a patient with orofacial clefting; a potential role of ZFHX4 and USP10

A girl with a unilateral cleft lip, alveolus and palate, tooth agenesis, and mild dysmorphic features, without a specific underlying syndrome diagnosis, was genotypically characterized and phenotypically described. Cleft gene panel analysis, single-nucleotide polymorphism (SNP) array, whole genome sequencing (WGS), whole exome sequencing, and quantitative PCR (Q-PCR) analysis were used as diagnostic tests. SNP array revealed a maternal deletion at 16q24.1, encompassing the cleft candidate gene USP10. WES revealed an additional de novo Loss-of-Function variant (p.(Asn838fs)) in the Zinc-Finger-Homeobox-4 (ZFHX4) gene. Q-PCR was performed to explore the effect of the ZFHX4 variant and the deletion in 16q24.1. The mRNA expression of a selection of putative target genes involved in orofacial clefting showed a lowered expression of USP10 (52%), CRISPLD2 (31%), and CRISPLD1 (1%) compared to the control. IRF6 showed no difference in gene expression. This case supports ZFHX4 as a novel cleft gene and suggests USP10 may contribute to the etiology of orofacial clefts in humans.     

Complex rearrangement of chromosomes 7q21.13-q22.1 confirms the ectrodactyly-deafness locus and suggests new candidate genes

Complex chromosomal rearrangements with more than two breakpoints are rare. We report on a 5-year-old girl, evaluated because of psychomotor delay, ectrodactyly of right hand and feet, craniofacial dysmorphic features, cleft palate, deafness, and tetralogy of Fallot. A standard karyotype suggested a small intrachromosomal duplication of chromosome 7q. The chromosomal rearrangement was characterized by mBAND, which disclosed a reciprocal interstitial translocation t(7;8)(q21q22;q23q24). FISH analysis and array-CGH analysis showed a paracentric inversion of 7q and a microdeletion of 7q21.13. The parents had normal chromosomes. The deletion found in the present patient confirms that candidate region of ectrodactyly-deafness (OMIM 220600) maps to 7q21 and suggests new candidate genes for that disorder. This patient also had facial features reminiscent of tricho-rhino-phalangeal syndrome and one chromosome breakpoint involved band 8q24, a locus for this disorder. In addition, FOG1 gene maps to 8q23 and has been implicated in a subset of subjects with tretralogy of Fallot. We suggest that the aberration of 8q may have contributed to her facial and cardiac findings.     

Genome-wide linkage analysis and mutation analysis of hereditary congenital blepharoptosis in a Japanese family

Hereditary congenital ptosis (PTOS) is defined as drooping of the upper eyelid without any other accompanying symptoms and distinguished from syndromic blepharoptosis. Two previous linkage analyses assigned a PTOS locus (PTOS1) to 1p32-p34.1 and another (PTOS2) to Xq24-q27.1. In addition, in a sporadic case with a balanced chromosomal translocation t(1;8) (p34.3;q21.12), the ZFHX4 (zinc finger homeodomain 4) gene was found to be disrupted at the 8q21.12 breakpoint, but there was no gene at the 1p34.3 breakpoint, suggesting the existence of the third PTOS locus (PTOS1) at 8q21.12. We carried out a genome-wide linkage analysis in a Japanese PTOS family and calculated two-point and multipoint log of odds (LOD) scores with reduced penetrance. Haplotype analysis gave three candidate disease-responsible regions, i.e., 8q21.11-q22.1, 12q24.32-q24.33, and 14q21.1-q23.2. Although the family size is too small to define one of them, 8q21.11-q22.1 is a likely candidate region, because it contains the previously reported translocation breakpoint above. We thus performed mutation, Southern-blot and methylation analyses of ZFHX4 but could not find any disease-specific change in the family. Nevertheless, our data may support the localization of PTOS1.     

A de novo 3.57 Mb microdeletion in 8q12.3q13.2 in a patient with mild intellectual disability and epilepsy

A female patient, nine years of age, is reported with a history characterized by delay of psychomotor and speech development, mild to moderate intellectual disability and persistent sleep disturbances since the age of two. The patient showed facial dysmorphisms, a pectus excavatum and a sandal gap. Apart from lowered intelligence, neuropsychological functioning disclosed impaired attentional capacities and executive control as well as weak motor skills. Genome wide SNP array analysis revealed a 3.57 Mb de novo microdeletion in band q12.3 of chromosome 8. The long lasting sleep disorders turned out to originate from a rare juvenile epilepsy, continuous spike-waves during slow sleep (CSWS) syndrome, that includes the electrical status epilepticus in sleep (ESES) phenomenon. MRI-scanning of the brain showed no abnormalities.To the authors knowledge, this is the first report of a de novo 8q12.3q13.2 microdeletion syndrome that presents with ESES/CSWS.     

Clinical and molecular characterization of 17q21.31 microdeletion syndrome in 14 French patients with mental retardation

Chromosome 17q21.31 microdeletion was one of the first genomic disorders identified by chromosome microarrays. We report here the clinical and molecular characterization of a new series of 14 French patients with this microdeletion syndrome. The most frequent clinical features were hypotonia, developmental delay and facial dysmorphism, but scaphocephaly, prenatal ischemic infarction and perception deafness were also described. Genotyping of the parents showed that the parent from which the abnormality was inherited carried the H2 inversion polymorphism, confirming that the H2 allele is necessary, but not sufficient to generate the 17q21.31 microdeletion. Previously reported molecular analyses of patients with 17q21.31 microdeletion syndrome defined a 493 kb genomic fragment that was deleted in most patients after taking into account frequent copy number variations in normal controls, but the deleted interval was significantly smaller (205 kb) in one of our patients, encompassing only the MAPT, STH and KIAA1267 genes. As this patient presents the classical phenotype of 17q21.31 syndrome, these data make it possible to define a new minimal critical region of 160.8 kb, strengthening the evidence for involvement of the MAPT gene in this syndrome.     

Two families with sibling recurrence of the 17q21.31 microdeletion syndrome due to low-grade mosaicism

The 17q21.31 microdeletion syndrome is characterised by intellectual disability, epilepsy, distinctive facial dysmorphism, and congenital anomalies. To date, all individuals reported with this syndrome have been simplex patients, resulting from de novo deletions. Here, we report sibling recurrence of the 17q21.31 microdeletion syndrome in two independent families. In both families, the mother was confirmed to be the parent-of-origin for the 17q21.31 deletion. Fluorescence in situ hybridisation analyses in buccal mucosa cells, of the mother of family 1, identified monosomy 17q21.31 in 4/50 nuclei (8%). In mother of family 2, the deletion was identified in 2/60 (3%) metaphase and in 3/100 (3%) interphase nuclei in peripheral lymphocytes, and in 7/100 (7%) interphase nuclei in buccal cells. A common 17q21.31 inversion polymorphism predisposes to non-allelic homologous recombination and hereby to the 17q21.31 microdeletion syndrome. On the basis of the 17q21.31 inversion status of the parents, we calculated that the probability of the second deletion occurring by chance alone was 1/14,438 and 1/4812, respectively. If the inversion status of the parents of a child with the 17q21.31 microdeletion syndrome is unknown, the overall risk of a second child with the 17q21.31 microdeletion is 1/9461. We conclude that the presence of low-level maternal somatic-gonadal mosaicism is associated with the microdeletion recurrence in these families. This suggests that the recurrence risk for parents with a child with a 17q21.31 microdeletion for future pregnancies is higher than by chance alone and testing for mosaicism in the parents might be considered as a helpful tool in the genetic counselling.     

Incomplete penetrance,variable expressivity,or dosage insensitivity in four families with directly transmitted unbalanced chromosome abnormalities

The direct transmission of microscopically visible unbalanced chromosome abnormalities (UBCAs) is rare and usually has phenotypic consequences. Here we report four families in which a normal phenotype was initially found in one or more family members. Each UBCA was interpreted with regard to overlapping examples and factors previously associated with transmitted imbalances including incidental ascertainment, low gene density, benign copy number variation (CNV) content, and gene relatedness. A 4.56 Mb deletion of 8p23.1‐p23.2 was thought to be causal in the affected proband but showed incomplete penetrance in her mother and sibling (Family 1). Incomplete penetrance was also associated with a 10.88 Mb duplication of 13q21.31‐q22.1 (Family 3) and dosage insensitivity with a 17.6 Mb deletion of 22pter‐q11.21 (Family 4) that were both ascertained at prenatal diagnosis and each found in 4 unaffected family members. The 22pter‐q11.21 deletion is part of a region with high benign CNV content and supports the mapping of cat eye syndrome to a 600 kb interval of 22q11.1‐q11.21. Low gene densities of less than 2.0 genes/Mb were found in each of these three families but only after segmentally duplicated genes were excluded from the deletions of 8p and 22q. In contrast, gene density was average and variable expressivity associated with a 3.59 Mb duplication of 8p23.1 incidentally ascertained for paternal infertility (Family 2). Our results indicate that a greater degree of direct parental transmission, incomplete penetrance, and variable expression are features of both sub‐microscopic CNVs and UBCAs with relatively low gene and high benign CNV content.

     

Nablus mask-like facial syndrome is caused by a microdeletion of 8q detected by array-based comparative genomic hybridization

In 2000, Teebi reported on a 4-year-old boy with a distinctive pattern of malformation, which he termed the "Nablus mask-like facial syndrome" (OMIM# 608156). Characterization of this syndrome has been difficult because of the paucity of patients described in the medical literature and its unknown etiology and pathogenesis. We present two patients with Nablus mask-like facial syndrome who both display a microdeletion in the 8q21-8q22 region detected by array-based comparative genomic hybridization. Patient 1, a boy, has a distinct facial appearance characterized by severe blepharophimosis, tight-appearing glistening facial skin, sparse and unruly hair, a flat and broad nose, and distinctive ears that are triangular in shape with prominent antihelices. He also demonstrates camptodactyly, contractures, unusual dentition, cryptorchidism, mild developmental delay, and a happy demeanor. Patient 2, a girl with a strikingly similar phenotype, was previously described in a report by Salpietro et al. 2003. She has distinctive ears, dental anomalies, and developmental delay. The etiology of her pattern of malformation was not identified at that time. Although high-resolution chromosome and subtelomeric FISH analyses were normal, array-based comparative genomic hybridization revealed an approximately 4 Mb deletion involving the 8q21.3-8q22.1 region in both patients. This region encompasses a number of genes that may contribute to this unique phenotype. These results demonstrate a chromosomal microdeletion as the etiology of Nablus mask-like facial syndrome and emphasize the diagnostic utility of array-based comparative genomic hybridization in the evaluation of multiple malformation syndromes of previously unrecognized causation.     

Genetic effects of a 13q31.1 microdeletion detected by noninvasive prenatal testing (NIPT)

Microdeletions of chromosome 13q31.1 are relatively rare. These types of deletions may cause different genetic effects on genotypes and/or phenotypes. There are several ways to detect microdeletions; noninvasive prenatal testing (NIPT) is the newest detection method. In this study, we aimed to investigate the genetic effects of a 13q31.1 microdeletion detected by NIPT and to reconfirm the feasibility of this procedure in predicting sub-chromosomal copy number variations (CNVs). The 13q31.1 microdeletion, which has previously been described as a disease-associated fragment, was detected by NIPT in a pregnant woman. To validate the finding and to explain the origin of this sub-chromosomal CNV, we collected fetal amniotic fluid and parental blood samples and tested the samples using array-based comparative genomic hybridization (aCGH). Karyotype analysis was performed on all of the samples to rule out balanced or mosaic anomalies. The aCGH results confirmed the NIPT findings. We detected the same type of microdeletion in the fetus and the mother via aCGH. The mother had a normal phenotype; therefore, in a post-test genetic counseling session, we predicted a normal phenotype for the fetus. After delivery, the normal phenotype of the newborn confirmed our prediction. Based on the present study, this 13q31.1 microdeletion may be considered as a chromosomal polymorphism. This study also reconfirmed the feasibility of obtaining a molecular karyotype of a fetus via NIPT.