Aneuploidy: the impact of chromosome imbalance on nuclear organization and overall genome expression.

The organization and dynamics of chromatin within the interphase nucleus as chromosome territories (CTs) and the relationship with transcriptional regulation are not fully understood. We studied a natural example of chromosomal disorganization: aneuploidy due to trisomies 13, 18 and 21. We hypothesized that the presence of an extra copy of one chromosome alters the CT distribution, which perturbs transcriptional activity. We used 3D-FISH to study the position of the chromosomes of interest (18 and 21) in cultured amniocytes and chorionic villus cells from pregnancies with a normal or aneuploid karyotype. We studied the volumes of nuclei and CTs in both conditions and performed a compared transcriptome analysis. We did not observe any differences between euploid and aneuploid cells in terms of the radial and relative CT positions, suggesting that the same rules govern nuclear organization in cases of trisomy. We observed lower volumes for CTs 18 and 21. Overall genome expression profiles highlighted changes in the expression of a subset of genes in trisomic chromosomes, while the majority of transcriptional changes concerned genes located on euploid chromosomes. Our results suggest that a dosage imbalance of the genes on trisomic chromosomes is associated with a disturbance of overall genomic expression.

Pregnancy outcomes in 188 French cases of prenatally diagnosed Klinefelter syndrome.

BACKGROUND: Klinefelter syndrome (KS), a common sex chromosome aneuploidy (47,XXY) is diagnosed prenatally with an incidence of 0.15%. The diagnosis is generally incidental, since there are no typical malformations on ultrasound (US). Once detected, genetic counseling is often difficult and the parents' decision to continue or terminate the pregnancy is greatly dependent on the amount and nature of the information provided. We sought to assess the pregnancy outcomes (i.e. continuation versus termination) and the influence of multidisciplinary centers for prenatal diagnosis on parental decisions in cases of KS. METHODS: From 1985 to 2009, 188 prenatal diagnoses of KS were made by 11 participating laboratories in mainland France. In each case, the karyotype indication, parental ages, year of prenatal testing, sampling procedure, karyotype, associated US findings and outcome were recorded. RESULTS AND CONCLUSIONS: The pregnancy termination rate declined markedly over time, from 46.9% before 1997 to 11.6% thereafter, in line with the introduction of new legislation on prenatal diagnosis for medical reasons and, more specifically, the creation of multidisciplinary prenatal diagnosis centers. However, an additional microdeletion in one KS infant who exhibited echogenic bowel on US was unfortunately diagnosed postnatally. This raises the question as to whether array comparative genomic hybridization should be prenatally advised when US abnormalities are detected, in line with advice for fetuses with a normal karyotype.

Is rapid aneuploidy screening used alone acceptable in prenatal diagnosis? An evaluation of the possible role of ultrasound examination.

OBJECTIVE: The objectives of this study were to use a factual basis to: (1) determine the number, nature, and probable phenotypic consequences of karyotype anomalies that would probably be missed (structural anomalies, uncommon aneuploidies and mosaic aneuploidies) by rapid aneuploidy screening (RAS), and (2) appraise whether RAS can replace traditional karyotyping when amniocenteses are performed for increased risk of Down's syndrome by maternal serum screening or advanced maternal age in the absence of ultrasound abnormality. METHODS: This retrospective cohort study analysed the indications, results and outcomes of 5,713 consecutive amniocenteses over a 5-year period at a single prenatal diagnosis centre in Paris. RESULTS: Advanced maternal age and increased Down's risk with maternal serum marker were the most common indications. Chromosome abnormalities were detected in 3.64% of the pregnancies tested, and unexpected structural anomalies in 0.63% (n = 36). Translocations were more likely to be reciprocal, balanced and of parental origin. There were 6 mosaic gonosomal aneuploidies. Overall, 4 mosaic autosomal aneuploidies and 36 structural aberrations would not have been recognised by RAS alone. Of the 4 mosaic autosomal aneuploidies, all were terminated, one had major malformations and the others had discrete signs that a good quality ultrasound examination would probably not detect. Of the 36 structural aberrations, 24 would be undetected by ultrasound scan, from which 6 would be associated with a significant risk of an abnormal phenotype outcome. CONCLUSION: In conclusion, our data do not provide evidence that RAS can replace the traditional karyotype. It is probably impossible to arrive in a universal conclusion of which approach (karyotype or RAS) is definitely better than the other. Each prenatal centre could have its own approach depending on the local data analysis, including quality control of ultrasounds.

Fetal loss after amniocentesis in a series of 5,780 procedures.

OBJECTIVES: Counseling on prenatal diagnosis requires accurate knowledge of the associated risks, including fetal loss. The objective of our study was to assess this risk of amniocentesis in a single center with several operators. METHODS: This retrospective analysis concerns only women with singleton pregnancies who underwent amniocentesis between 14(+0) and 23(+6) weeks' gestation. RESULTS: During this 4.5-year period, 5,780 amniocenteses were performed, of which we analyzed 5,319. The rate of fetal loss was 70 in 4,858 tests (1.4%), with a lost-to-follow-up rate of 3.8%. CONCLUSION: Our results for fetal loss are comparable to those in the largest series with fewer operators already published.

Large-scale deletions and SMADIP1 truncating mutations in syndromic Hirschsprung disease with involvement of midline structures.

Hirschsprung disease (HSCR) is a common malformation of neural-crest-derived enteric neurons that is frequently associated with other congenital abnormalities. The SMADIP1 gene recently has been recognized as disease causing in some patients with 2q22 chromosomal rearrangement, resulting in syndromic HSCR with mental retardation, with microcephaly, and with facial dysmorphism. We screened 19 patients with HSCR and mental retardation and eventually identified large-scale SMADIP1 deletions or truncating mutations in 8 of 19 patients. These results allow further delineation of the spectrum of malformations ascribed to SMADIP1 haploinsufficiency, which includes frequent features such as hypospadias and agenesis of the corpus callosum. Thus, SMADIP1, which encodes a transcriptional corepressor of Smad target genes, may play a role not only in the patterning of neural-crest-derived cells and of CNS but also in the development of midline structures in humans.

Prenatal diagnosis of Niemann-Pick type C disease: current strategy from an experience of 37 pregnancies at risk.

Thirty-seven pregnancies at risk for Niemann-Pick type C disease were monitored by study of cultured amniotic fluid cells (8 cases) or chorionic villus cells (29 cases) in 23 couples over the period 1984-91. An early protocol combined determination of sphingomyelinase activity with electron microscopy. The current strategy, based on the demonstration of specific abnormalities in intracellular processing of exogenous cholesterol, combines the study of the early phase (first 6 h) of LDL-induced cholesteryl ester formation and the histochemical evaluation (filipin staining after 24 h of LDL uptake) of the LDL-induced accumulation of unesterified cholesterol. Thirteen fetuses were predicted to be affected. Confirmation of the diagnosis was made by study of cholesterol processing in fetal skin fibroblast cultures and/or by demonstration of a characteristic lipid storage in fetal liver, already present at 14 w gestation. Definition of the biochemical phenotype (classical, variant, or intermediate) of the index case, with regard to cholesterol-processing abnormalities, is an absolute prerequisite to adequate genetic counseling in a given family. Prenatal diagnosis has now proved a safe procedure in the predominant (approximately 85%) group of families with the classical phenotype.

Chromosomal prenatal diagnosis: study of 936 cases of intrauterine abnormalities after ultrasound assessment.

Nine hundred and thirty-six prenatal chromosomal analyses were performed by four cytogenetic centres after ultrasound diagnosis of fetal abnormalities, amniotic fluid disorders, fetal growth retardation, and fetal or placental abnormalities. During the same period, 6515 fetal karyotypes were analysed because of maternal age. Frequencies of chromosomal aberrations in each case were respectively 4.4, 6.7 and 15.8 per cent, compared with 3.18 per cent when the fetal karyotype was performed because of maternal age. High rates of chromosomal aberrations are observed in cases of cervical hygroma, limb abnormalities, omphaloceles, duodenal stenosis, hydrocephalus, and facial abnormalities. In the case of polymalformations, this rate was 29.2 per cent. When malformations were seen together with an amniotic fluid disorder or growth retardation, 21.5 per cent chromosomal aberrations were observed. This frequency was 10.4 per cent when growth retardation was associated with an amniotic fluid disorder. Trisomy 13, 18, 21 and monosomy X accounted for 4/5 of all abnormalities in which we observed a high rate of triploidies (4.9 per cent) and balanced (3.3 per cent) or unbalanced (9.8 per cent) non-Robertsonian structural abnormalities. Sonographic ascertainment of these aberrations and prenatal characteristics of major anomalies are discussed.

[The placenta and trisomies 13, 18, 21]. / Placenta et trisomies 13, 18, 21.

In 30 cases of trisomies 13, 18 and 21, the placenta showed different lesions of hypotrophy, immaturity, hydrops, trophoblastic recurrences or cysts and mineralisation of the trophoblastic basal lamina. These are non specific lesions and can be observed in a variety of conditions, but their association is striking in most cases of trisomies. Different pathological patterns may thus evoke a trisomy, though that diagnosis can only be ascertained by chromosome analysis.

[Chorionic villi sampling. Results with the first 500 samples]. / Prélèvements de villosités choriales. Expérience des 500 premiers prélèvements.

531 chorionic villi forceps biopsies were carried out, to look for genetic diseases. Sampling was impossible in 24 cases (4.5%). The following indications were chosen: maternal age over 38 years: 361 cases; parental chromosome abnormality: 28 cases; previous history of chromosome abnormality: 21 cases; X-linked disease: 77 cases; metabolic disease: 32 cases; hemoglobinopathy: 7 cases; blood group determination: 5 cases. An elective abortion was carried out in 44 cases (8.7%), whereas 465 pregnancies were not interrupted. Full term has been reached in 327 pregnancies. The rate of miscarriage in this group is 3.9% (13 miscarriages out of 327 pregnancies followed). The results obtained at the Saint-Vincent-de-Paul Hospital show that the cytogenetic technique is reliable, and that the low risk of sampling allows its application in the diagnosis of chromosome anomalies.

Agyria--pachygyria and Miller-Dieker syndrome: clinical, genetic and chromosome studies.

Twelve cases of lissencephaly are reported. A high resolution chromosome study was performed on each in order to detect small chromosomal anomalies, undetectable with routine techniques. Only one case was shown to have an unbalanced karyotype with a microdeletion of the short arm of chromosome 17 (del 17p). This child also had symptoms of the Miller-Dieker syndrome, consisting of lissencephaly, characteristic facies, pre- and post-natal growth retardation and other birth defects. As proposed by Dobyns, it seems justifiable to classify lissencephalies into four different groups, according to other clinical manifestations and results of chromosome studies.

Interstitial dup(1p) and severe intrauterine growth retardation.

An 1,860 g baby girl was born spontaneously after a 38 weeks pregnancy with important foetal hypotrophy and died at 6 weeks of life. She had an inverted duplication of a small part of the short arm of chromosome 1p:46, XX, inv dup(1) (pter p31::p11p13::p31 ter). This observation is compared to three others reported in the literature with intrachromosomal duplication of 1p.

Immediate prenatal diagnosis of Zellweger syndrome by direct measurement of very long chain fatty acids in chorionic villus cells.

We report a gas chromatographic-mass spectrometric method which allows the very long chain fatty acids content of trophoblastic tissue to be directly measured in samples collected by biopsy between 8 and 11 weeks of gestation. This method has been successfully applied to the detection of fetal Zellweger syndrome in two pregnant women who had previously delivered affected infants. In one of them, increased concentrations of C26:0 (0.254 versus 0.108 +/- 0.035 microgram/mg proteins) and C24:0 (1.32 versus 0.815 +/- 0.325 microgram/mg proteins) in trophoblast indicated that the fetus had Zellweger syndrome, a diagnosis confirmed by pathological findings after abortion. In the second case, the pregnancy was allowed to proceed, on the basis of normal concentrations of very long chain fatty acids in trophoblastic tissue, and its outcome was actually a healthy newborn.

De novo inv del(4) in an infant with the Wolf-Hirschhorn syndrome.

An infant was found to have a de novo complex rearrangement of one chromosome 4. Her karyotype was interpreted as 46,XX,inv del(4)(pter::p16.3::q31.2----p15.2::q31.2----qter). Clinically she showed the features of the Wolf-Hirschhorn syndrome.

Lysosomal hydrolase activity in chorionic villi and embryonic cells in culture.

Fourteen lysosomal enzymes were compared in 20 cultured cell lines from chorionic biopsy and corresponding embryonic tissue after voluntary abortions. Enzymatic expression appears to be similar in cultured cells from both sources with some slightly higher levels for chorionic villi. We stress the importance of culturing chorionic villi especially in the case of enzymes (alpha-L-iduronidase) or diseases (I cell disease) whose expression is unusual in fresh trophoblast tissue.

[Sampling, culturing and karyotyping of chorionic villi]. / Prélèvement, culture et caryotype des villosités choriales.

The authors report on 69 samples of chorionic villi taken from patients who were undergoing therapeutic termination of pregnancy. These samples were taken using small forceps which were guided by ultrasound. The reliability and the chances of culturing these villi in order to work out the caryotype of the fetus and to study the enzymes is discussed.

Unexpected structural chromosome rearrangements in prenatal diagnosis.

Among 5315 prenatal diagnoses performed for various indications (maternal age, neural tube defect, metabolic diseases, X-linked diseases, pathologic pregnancies) 29 unexpected structural chromosome rearrangements were found in fetal cells. Fourteen were de novo chromosome rearrangements, six unbalanced, and eight balanced. Fifteen were inherited and balanced rearrangements. This high frequency of structural anomalies is discussed.