Prenatal diagnosis and molecular characterization of a novel locus for Dandy-Walker malformation on chromosome 7p21.3

We present three foetuses with Dandy-Walker malformation, intra-uterine growth restriction and multiple congenital abnormalities, who were studied by array-based comparative genomic hybridization and revealed a novel locus on chromosome 7p21.3. The association of pure chromosome 7p aberrations with Dandy-Walker malformation has rarely been reported. The present study suggests that the critical region associated with Dandy-Walker malformation is restricted to 7p21.3, including the cerebellar disease associated genes NDUFA4 and PHF14.     

Prenatal diagnosis of tetralogy of Fallot associated with chromosome 22q11 deletion

Microdeletion of 22q11 is responsible for DiGeorge syndrome, velocardiofacial syndrome, congenital conotruncal heart defects, and related disorders. We report our experiences on prenatal diagnosis by fluorescence in situ hybridization (FISH) for 22q11 deletion in two fetuses with tetralogy of Fallot. Karyotyping and FISH of the parents revealed that one fetus inherited the disease from maternal microdeletion. These findings suggest the importance of performing FISH in pregnancies with prenatally detected tetralogy of Fallot.     

两例Y染色体部分缺失胎儿的产前诊断

目的对两例Y染色体部分缺失胎儿进行产前诊断。方法采用常规G显带及C显带技术分析胎儿及父亲的核型,采用荧光原位杂交(fluorescence in situ hybridization,FISH)、染色体拷贝数变异检测技术(copy number varaition sequencing,CNV-seq)性别决定基因(sex region of Y chromosome,SRY)检测技术及无精子因子(azoospermia factor,AZF)检测技术检测胎儿DNAO结果2例胎儿羊水染色体在320〜400条带水平均提示46,XN,del(Y)(qll.2),Y染色体着丝粒探针FISH检测结果均提示Y染色体数目未见异常。2例胎儿父亲外周血染色体核型均未见明显异常。胎儿羊水DNA拷贝数检测提示一例胎儿Y染色体q 11.221-ql2处缺失12.88 Mb,涉及全部AZFb+AZFc区域;另一例胎儿Y染色体qll.21-ql2处缺失14.84 Mb,涉及全部AZF区域。2例胎儿羊水SRY基因检测提示SRY基因阳性,SKY基因编码区未检测到已报道的致病点突变。2例胎儿基因检测提示存在AZF部分或全部缺失。结论联合多种技术有助于明确诊断Y染色体结构异常。CNV-seq检测有利于快速筛查胎儿Y染色体微缺失,可做为对染色体核型分析的补充和验证的方法。     

Prenatal diagnosis of chromosome 4 mosaicism: prognostic role of cytogenetic, molecular, and ultrasound/MRI characterization

Trisomy 4 mosaicism is extremely rare: herein we report the cytogenetic and molecular characterization and prenatal US findings of a case diagnosed prenatally. The diagnosis of level III mosaicism was established in cultured amniotic fluid cells (22.5%). At 22 weeks gestation, micrognathia and hypotelorism were suspected at 2-D sonography, and confirmed at 3-D examination. In addition, 2-D US showed cerebellar hypoplasia associated with borderline ventriculomegaly (confirmed at magnetic resonance imaging, MRI), spine deformity (hemivertebra), and a complete atrioventricular septal defect (AVSD). The pregnancy was terminated. Trisomy 4 mosaicism was confirmed in placental and fetal skin cultured cells. The cord blood karyotype was normal. Molecular analysis excluded uniparental disomy of chromosome 4, and indicated that the trisomy 4 was of maternal meiotic origin. In presence of chromosome 4 mosaicism, accurate fetal sonography and echocardiography are mandatory. Low level mosaicism and normal echographic examinations seem to be associated with good prognosis. In postnatal life, chromosome 4 mosaicism should be suspected, and cytogenetic analysis proposed of further tissues (i.e., skin), in presence of craniofacial dysmorphism, cardiac defects, and abnormal hands/feet, even if mental development is appropriate or only slightly impaired.     

Prenatal diagnosis of a fetus with two balanced de novo chromosome rearrangements

Two apparently balanced chromosome rearrangements were identified in a 17-week fetus by analysis of cultured amniocytes. The fetal karyotype was 46,XX,t(2;16) (q33; q24), inv(7)(p15q11.23). Parental karyotypes were normal, indicating a de novo origin of both chromosome rearrangements in the fetus. The risk of phenotypic abnormality from a de novo reciprocal translocation or inversion has been estimated at approximately 7% [Warburton, 1991]. The risk of abnormality in this fetus was estimated to be a minimum of 14%, based on the additive risk of each rearrangement, equivalent to 3.5% per chromosome breakpoint. The pregnancy was terminated because of the risk of abnormality and the detection of intrauterine growth retardation by ultrasound. In the absence of additional experience, the minimum presumed risk of phenotypic abnormality for de novo, multiple or complex chromosome rearrangements identified prenatally may be estimated as the additive risk of the number of chromosome breakpoints involved. © 1996 Wiley-Liss, Inc.     

Clinical and molecular characterization of an emerging chromosome 22q13.31 microdeletion syndrome

Microdeletion of chromosome 22q13.31 is a very rare condition. Fourteen patients have been annotated in public databases but, to date, a clinical comparison has not been done and, consequently, a specific phenotype has not been delineated yet. We describe a patient showing neurodevelopmental disorders, dysmorphic features, and multiple congenital anomalies in which SNP array analysis revealed an interstitial 3.15 Mb de novo microdeletion in the 22q13.31 region encompassing 21 RefSeq genes and seven non‐coding microRNAs. To perform an accurate phenotype characterization, clinical features observed in previously reported cases of 22q13.31 microdeletions were reviewed and compared to those observed in our patient. To the best of our knowledge, this is the first time that a comparison between patients carrying overlapping 22q13.31 deletions has been done. This comparison allowed us to identify a distinct spectrum of clinical manifestations suggesting that patients with a de novo interstitial microdeletion involving 22q13.31 have an emerging syndrome characterized by developmental delay/intellectual disability, speech delay/language disorders, behavioral problems, hypotonia, urogenital, and hands/feet anomalies. The microdeletion identified in our patient is the smallest reported so far and, for this reason, useful to perform a detailed genotype‐phenotype correlation. In particular, we propose the CELSR1, ATXN10, FBLN1, and UPK3A as candidate genes in the onset of the main clinical features of this contiguous gene syndrome. Thus, the patient reported here broadens our knowledge of the phenotypic consequences of 22q13.31 microdeletions facilitating genotype‐phenotype correlations. Additional cases are needed to corroborate our hypothesis and confirm genotype–phenotype correlations of this emerging syndrome.

     

肾上腺脑白质营养不良的产前分子诊断

目的对2名来自不同家系的肾上腺脑白质营养不良携带者所怀胎儿进行产前分子诊断。方法在采用STR位点分析方法排除母体基因组DNA污染后，应用扩增阻滞突变系统和DNA斑点杂交的方法对胎儿1羊水基因组DNA进行检测，应用PCR-RFLP和DNA序列测定对胎儿2羊水基因组DNA进行分析。结果在针对R617G突变的扩增阻滞突变系统中，当使用突变引物时，从胎儿1羊水DNA、胎儿1母亲基因组DNA均扩增出185bp的预期特异性条带，而胎儿1父亲和对照则未扩出。在斑点杂交反应中，应用R617G突变型探针时，只有胎儿1羊水细胞及其母亲外周血基因组DNA出现特异性显色斑点。在第2个家系中，先用PCR扩增出横跨P534R突变位点的基因组DNA片段（506bp），应用HoeⅡ酶切此产物，胎儿2以及其父亲、无关对照均未见切割，其母亲的部分产物被切割成396bp和110bp两个片段。对此PCR产物进行DNA序列测定，未在胎儿2中检测出P534R突变。结论胎儿1带R617G突变，为肾上腺脑白质营养不良半合子；胎儿2不带P534R突变，为正常半合子。     

Supernumerary marker chromosomes derived from chromosome 6: cytogenetic, molecular cytogenetic, and array CGH characterization

Supernumerary marker chromosomes (SMC) are relatively common in prenatal diagnosis. As the clinical outcomes vary greatly, a better understanding of the karyotype-phenotype correlation for different SMCs will be important for genetic counseling. We present two cases of prenatally detected de novo, small SMCs. The markers were present in 80% of amniocyte colonies in Case 1 and 38% of the colonies in Case 2. The SMCs were determined to be derived from chromosome 6 during postnatal confirmation studies. Although the sizes and the chromosomal origin of the SMCs in these two cases appeared to be similar, the clinical outcomes varied. The clinical manifestations observed in Case 1 included small for gestational age, feeding difficulty at birth, hydronephrosis, deviated septum and dysmorphic features, while the phenotype is apparently normal in Case 2. Array comparative genomic hybridization (CGH) was performed and showed increase in dosage for approximately 26 Mb of genetic material from the proximal short and long arms of chromosome 6 in Case 1. Results of array CGH were uninformative in Case 2, either due to mosaicism or lack of detectable euchromatin. The difference in the clinical presentation in these two patients may have resulted from the difference in the actual gene contents of the marker chromosomes and/or the differential distribution of the mosaicism.     

Molecular cytogenetic characterization of two small chromosome 8 derived supernumerary mosaic markers

Two small supernumerary mosaic marker chromosomes (SMC) were identified by conventional cytogenetics, one prenatally, the other postnatally. Fluorescence in situ hybridization (FISH) techniques, including 24-color FISH, were applied to identify both SMCs and better characterize their constitution. Patient 1: a 29 year-old man, whose wife had a spontaneous abortion, was found to have a small ring of the pericentromeric region of chromosome 8 (47,XY,+r(8)(p11q11)/46,XY). Patient 2: a 37 year-old woman had amniocentesis. The fetus was found to have a SMC; its presence was confirmed postnatally. Several FISH techniques (24-color, whole chromosome paints, centromeres, telomeres, band 8p22) led to the identification of a small analphoid marker. The marker was an inversion-duplication for part of the short arm of chromosome 8 (47,XY,+inv dup (8)(p23pter)/46,XY). The 24-color FISH allowed us to conclude that both markers originated exclusively from chromosome 8. However, the structure and content of the markers were elucidated using other molecular cytogenetic techniques, showing their complementarity.     

Prenatal diagnosis by FISH of a 22q11 deletion in two families.

We report on prenatal diagnosis by FISH of a sporadic 22q11 deletion associated with DiGeorge syndrome (DGS) in two fetuses after an obstetric ultrasonographic examination detected cardiac anomalies, an interrupted aortic arch in case 1 and tetralogy of Fallot in case 2. The parents decided to terminate the pregnancies. At necropsy, fetal examination showed characteristic facial dysmorphism associated with congenital malformations, confirming full DGS in both fetuses. In addition to the 22q11 deletion, trisomy X was found in the second fetus and a reciprocal balanced translocation t(11;22) (q23;q11) was found in the clinically normal father of case 1. These findings highlight the importance of performing traditional cytogenetic analysis and FISH in pregnancies with a high risk of having a deletion.     

两例父源性17q12微缺失综合征胎儿的产前诊断和遗传学分析

目的:探讨两例父源性17q12微缺失综合征胎儿的产前诊断和遗传咨询。方法:一名孕妇的两例胎儿的孕中晚期超声检查均提示肾脏异常和羊水过多,应用单核苷酸多态性分析(single nucleotide polymorphism array,SNP-array)分别对第1胎的脐血样本和第2胎的羊水样本进行产前诊断。发现第1胎染...     

Familial transmission of a deletion of chromosome 21 derived from a translocation between chromosome 21 and an inverted chromosome 22

Chromosome analysis of a newborn boy with Down syndrome resulted in the identification of a family with an unusual derivative chromosome 22. The child has 46 chromosomes, including two chromosomes 21, one normal chromosome 22, and a derivative chromosome 22. Giemsa banding and fluorescent in situ hybridization (FISH) studies show that the derivative chromosome is chromosome 22 with evidence of both paracentric and pericentric inversions, joined to the long arm of chromosome 21 from 21q21.2 to qter. The rearrangement results in partial trisomy 21 extending from 21q21.2 to 21q terminus in the patient. The child's mother, brother, maternal aunt, and maternal grandmother are all carriers of the derivative chromosome. All have 45 chromosomes, with one normal chromosome 21, one normal chromosome 22, and the derivative chromosome 22. The rearrangement results in the absence of the short arm, the centromere, and the proximal long arm of chromosome 21 (del 21pter21q21.2) in carriers. Carriers of the derivative chromosome in this family have normal physical appearance, mild learning disabilities and poor social adjustment. Am. J. Med. Genet. 70:399–403, 1997. © 1997 Wiley-Liss, Inc.     

Prenatal diagnosis and molecular characterization of an interstitial 1q24.2q25.2 deletion

We report on the observation of an interstitial deletion of the long arm of chromosome 1 diagnosed prenatally in a 28 weeks gestation fetus by standard karyotype. Amniocentesis was performed because of an increased Down syndrome maternal serum screening and ultrasonographic abnormalities. Fetus autopsy showed an intrauterine growth retardation, dysmorphic features and limbs abnormalities. Using fluorescent in situ hybridization technique (FISH), we characterized the deletion boundaries corresponding to the bacterial artificial chromosomes (BAC) RP11-193J5 and RP11-162L13. Molecular studies identified the deletion of paternal origin. Therefore the karyotype was interpreted as 46,XY,del(1)(q24.2q25.2). This is the smallest deletion of the long arm of chromosome 1 reported prenatally and characterized at the molecular level. Its phenotype is compared to other similar cases described in the literature.     

Molecular and phenotypic characterization of ring chromosome 22

We performed a phenotype study of 35 individuals (19 males, 16 females) with ring chromosome 22 or r(22) with a mean age of 10 years. In common with other studies, a phenotype of moderate-to-profound learning difficulties and delay or absence of speech affected all individuals with the exception of the case with the smallest deletion. Autistic traits were significantly associated with r(22), as shown by an autism screening questionnaire. Mild and variable dysmorphic features, predominantly craniofacial and distal limb, were observed. Internal organ involvement was uncommon. Even though ring chromosomes are reportedly associated with growth abnormalities, only 2 out of 24 individuals showed evidence of growth failure, while 2 showed accelerated growth. Chromosome 22 long arm deletions, as determined by hemizygosity for informative microsatellite markers, varied from <67 kb to 10.2 Mb in size (or <0.15 to 21% of total chromosome length), with no significant differences in the parental origin of the ring chromosome. Few phenotypic features correlated with deletion size suggesting a critical gene, or genes, of major effect lies close to the telomere. Loss of the SHANK3/PROSAP2 gene has been proposed to be responsible for the main neurological developmental deficits observed in 22q13 monosomies. This study supports this candidate gene by identifying a phenotypically normal r(22) individual whose ring chromosome does not disrupt SHANK3. All other r(22) individuals were hemizygous for SHANK3, and we propose it to be a candidate gene for autism or abnormal brain development.     

三例22号染色体异常胎儿的产前遗传学分析

目的应用超声以及多种遗传学检测技术对3例产前筛查提示染色体可能异常的胎儿进行分析,为遗传咨询提供依据。方法对3例孕妇进行胎儿超声检查、核型分析、单核苷酸多态性微阵列芯片(single nucleotide polymorphism-based microarray,SNP-Array)检测,并通过荧光原位杂交(fluorescence in situ hybridization,FISH)对结果进行验证。结果三例胎儿均发现22号染色体存在异常。例1在22q13.2q13.33区存在7.1 Mb的杂合缺失,涉及SHANK3、FBLN1等54个OMIM基因;例2为嵌合体核型,约12%的细胞22q13.31q13.33区存在6.6 Mb的杂合缺失,覆盖SHANK3、PPARA等48个OMIM基因,另有5%的细胞22q11.1q13.2区存在26.1 Mb的拷贝重复,覆盖285个OMIM基因;例3在22q11.1q11.21区存在1.7 Mb的二次重复,涉及CECR1、CECR2、ATP6V1E1等10个OMIM基因。三例胎儿父母的核型及SNP-Array检测结果均未见异常,提示胎儿为新发变异。结论22号染色体微缺失/微重复所致疾病的严重性不仅与其范围有关,还与染色体结构、基因剂量及环境等密切相关。在产前诊断中综合运用超声和多种遗传学检测技术可以显著提高表型变异较大的遗传学异常的检出率。     

Prenatal and postnatal diagnosis of 22q11.2 deletion syndrome

Microdeletion of chromosome 22q11.2, the most common human deletion syndrome encompasses a wide spectrum of abnormalities. Many clinical or ultrasonographic findings may support deletion studies, either in utero or in the post-natal period. The objective of our study was to evaluate the circumstances of 22q11.2 deletion diagnosis in a single centre of genetics during a 12 years period. Testing for 22q11.2 deletion was performed in 883 cases. Congenital heart defect was the most common reason for referral. An antenatal 22q11.2 microdeletion was detected in 8 fetuses (4.7%) among 169 pregnancies, all presenting conotruncal anomalies. In one case prenatal diagnosis led to the identification of the deletion in the mildly affected father and had negative impact on the family. During the same period, postnatal 22q11.2 DS was diagnosed in 81 out of 714 patients aged from birth to 42 years (11.3%) (p = 0.02). A CHD was present in 37 (45.7%). This figure is significantly lower than the 75% commonly reported. These results suggest that deletion studies could be justifiable in fetuses with non-cardiac prenatal sonographic findings that have been reported in association with 22q11.2 DS. However, as most of these malformations are rather common and non specific, systematic 22q11.2 testing is not justifiable. In such cases, careful cardiac and thymus examination could provide additional clues for 22q11.2 testing. In addition parents should be given accurate information before antenatal or postnatal testing, including the wide variability of the clinical phenotype, the impossibility to establish a precise prognosis concerning psychomotor development and psychiatric risks.     

Prenatal detection and molecular characterization of a de novo duplication of the distal long arm of chromosome 19

A tandem duplication of the distal long arm of chromosome 19 was identified in a 10 week fetus by analysis of chorionic villi. The fetal karyotype from two primary cultures was 46,XY,dir dup(19)(q13.2q13.4). The origin of the extra material was confirmed by fluorescence in situ hybridization using a chromosome 19 whole chromosome probe. Parental chromosomes were normal, indicating a de novo origin of the extra chromosome material. This is the first case of dup(19q) detected by prenatal diagnosis. Molecular studies demonstrated that the duplication involved a maternal chromosome 19. Am. J. Med. Genet. 71:325–328, 1997. © 1997 Wiley-Liss, Inc.     

Prenatal diagnosis of a de novo ring chromosome 11

Ring chromosomes are uncommon findings in prenatal diagnosis. Growth retardation is the most significant manifestation, in particular among patients with rings of larger chromosomes. A 30-year-old gravida 1, para 0 white woman was referred for genetic counseling because of maternal anxiety. Cytogenetic analysis of amniotic fluid cells at 16 weeks gestation revealed an abnormal mosaic female chromosome complement; 46,XX,r(11)(p15q25)[14]/45,XX,-11[7]. The ring 11 showed no detectable loss of chromosomal material at 450 band level. Both parents had a normal karyotype. Fluorescence in situ hybridization demonstrated intact subtelomeric regions in the ring chromosome. A targeted ultrasound evaluation at the time of consultation suggested no significant abnormalities. The parents were counseled and subsequently decided to terminate the pregnancy. The autopsy revealed an immature female fetus with abnormal craniofacial features including brachycephaly, low-set ears and hypertelorism, bicornuate uterus, and calcifications in the renal tubules. The abnormal phenotypes could be a consequence of the ring instability, submicroscopic deletion, and/or alteration of genetic material at the site of fusion.     

Prenatal diagnosis of chromosome 15 abnormalities in the Prader-Willi/Angelman syndrome region by traditional and molecular cytogenetics

With improvements in culturing and banding techniques, amniotic fluid studies now achieve a level of resolution at which the Prader-Willi syndrome (PWS) and Angelman syndrome (AS) region may be questioned. Chromosome 15 heteromorphisms, detected with Q- and R-banding and used in conjunction with PWS/AS region-specific probes, can confirm a chromosome deletion and establish origin to predict the clinical outcome. We report four de novo cases of an abnormal-appearing chromosome 15 in amniotic fluid samples referred for advanced maternal age or a history of a previous chromosomally abnormal child. The chromosomes were characterized using G-, Q-, and R-banding, as well as isotopic and fluorescent in situ hybridization of DNA probes specific for the proximal chromosome 15 long arm. In two cases, one chromosome 15 homolog showed a consistent deletion of the ONCORPWS/AS region A and B. In the other two cases, one of which involved an inversion with one breakpoint in the PWS/AS region, all of the proximal chromosome 15 long arm DNA probes used in the in situ hybridization were present on both homologs. Clinical follow-up was not available on these samples, as in all cases the parents chose to terminate the pregnancies. These cases demonstrate the ability to prenatally diagnose chromosome 15 abnormalities associated with PWS/AS. In addition, they highlight the need for a better understanding of this region for accurate prenatal diagnosis. © 1995 Wiley-Liss, Inc.     

Prenatal diagnosis of a constitutional interstitial deletion of chromosome 5 (q15q31.1) presenting with features of congenital contractural arachnodactyly

Prenatal diagnosis of a constitutional interstitial deletion of chromosome 5 (q15q31.1) in a 30-year-old woman is reported. At 21 weeks of pregnancy, routine fetal ultrasounds showed the presence of apparently isolated bilateral club feet. Fetal karyotyping documented an interstitial deletion of the long arm of chromosome 5: 46,XX,del(5) (q15q31) in all 50 analyzed metaphases. Because such deletion is associated with severe psychomotor retardation, the pregnancy was terminated. Postmortem karyotyping of skin fibroblasts confirmed the presence of this interstitial de novo deletion in all mitoses. The breakpoints on 5q were analyzed by fluorescent in situ hybridization and were localized at 5q15 and q31.1. This case illustrates the importance of fetal karyotyping in cases of isolated club feet. At autopsy, the fetus presented had minor anomalies and contractures of knee and hip joints. These clinical findings could fit the diagnosis of congenital contractural arachnodactyly (CCA) or Beals syndrome. CCA is caused by a defect in the fibrillin-2 (FBN2) gene. This gene was previously mapped on 5q23-31. Our molecular studies of both parents and the fetus, using an intragenic polymorphic GT repeat, showed that the FBN2 gene was deleted in the fetus and that the de novo interstitial deletion occurred on the paternally inherited chromosome 5. Thus, CCA may be caused by a loss of function of the FBN2 gene. Clinical findings in this fetus and those of other described cases with interstitial 5q deletions are reviewed, and similarities with CCA are stressed. Am. J. Med. Genet. 77:188–197, 1998. © 1998 Wiley-Liss, Inc.