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PubMed1997

Meiotic origin of trisomy in confined placental mosaicism is correlated with presence of fetal uniparental disomy, high levels of trisomy in trophoblast, and increased risk of fetal intrauterine growth restriction.

Molecular studies were performed on 101 cases of confined placental mosaicism (CPM) involving autosomal trisomy. The origin of the trisomic cell line was determined in 54 cases (from 51 pregnancies), 47 of which were also analyzed for the presence of uniparental disomy (UPD) in the disomic cell line. An additional 47 cases were analyzed for parental origin in the disomic cell line only. A somatic (postmeiotic) origin of the trisomy was observed in 22 cases and included the majority of cases with CPM for trisomy 2, 7, 8, 10, and 12. Most cases of CPM involving trisomy 9, 16, and 22 were determined to be meiotic. Fetal maternal UPD was found in 17 of 94 informative CPM cases, involving trisomy 2 (1 case), 7 (1 case), 16 (13 cases), and 22 (2 cases). The placental trisomy was of meiotic origin in all 17 cases associated with fetal UPD (P = .00005). A meiotic origin also correlated with the levels of trisomy in cultured chorionic villi samples (CVS) (P = .0002) and trophoblast (P = .00005). Abnormal pregnancy outcome (usually IUGR) correlated with meiotic origin (P = .0003), the presence of fetal UPD (P = 4 x 10(-7)), and the level of trisomy in trophoblast (P = 3 x 10(-7)) but not with the level of trisomy in CVS or term chorion. The good fit of somatic errors with the expected results could have been observed only if few true meiotic errors were misclassified by these methods as a somatic error. These data indicate that molecular determination of origin is a useful predictor of pregnancy outcome, whereas the level of trisomy observed in cultured CVS is not. In addition, UPD for some chromosomes may affect prenatal, but not postnatal, development, possibly indicating that imprinting effects for these chromosomes are confined to placental tissues.

Cells, Cultured↗
PubMed2000

Recurrent trisomy 21 in a couple with a child presenting trisomy 21 mosaicism and maternal uniparental disomy for chromosome 21 in the euploid cell line.

Recurrence of trisomy 21 was observed in a family in which both parents had a normal chromosome complement. Mosaic trisomy 21 was found in a blood karyotype of the first child, a second pregnancy ended in spontaneous abortion, and a full trisomy 21 was found at prenatal diagnosis of the third pregnancy of this same couple. Although recurrent trisomy 21 may be due to chance, the possibility of germline mosaicism for trisomy 21 in one of the parents has important implications for recurrence risk. Molecular analysis was therefore undertaken in this family to determine the parental origin and the stage of nondisjunction of the extra chromosome 21 in both cases. Although a maternal origin of both instances of trisomy 21 was observed, the mosaic case showed homozygosity for all markers along the duplicated maternal chromosome. Such a finding would normally suggest a postzygotic origin of the trisomy 21. However, the diploid cell line in this same case showed maternal uniparental disomy 21, implying that it was the result of a trisomic conception. We suggest that a somatic nondisjunction in the maternal germ cells is the most likely explanation for these findings. The apparent meiotic II stage of nondisjunction of the nonmosaic trisomy 21 fetus was consistent with maternal mosaicism. A review of the literature for recurrent trisomy 21 cases studied by molecular means, suggests that mosaicism in germ cells may account for more cases than is detected cytogenetically. These results also show that DNA marker analysis does not provide a valuable tool for patient counseling in case of recurrent trisomy 21.

Child↗
PubMed2001

First trimester maternal serum placenta growth factor (PIGF)concentrations in pregnancies with fetal trisomy 21 or trisomy 18.

Placenta growth factor (PIGF), an angiogenic factor belonging to the vascular endothelial growth factor family, pregnancy-associated plasma protein A (PAPP-A) and free beta-human chorionic gonadotrophin (beta-hCG) were measured in maternal serum from 45 pregnancies with trisomy 21, 45 with trisomy 18 and 493 normal controls at 10-13 completed weeks of gestation. In the normal pregnancies maternal serum PIGF levels increased exponentially with gestation. The median multiple of the median (MoM) PIGF concentration in the trisomy 21 group (1.26 MoM) was significantly higher (p<0.0001) than in the control group (1.00 MoM). In the trisomy 18 group the median PIGF was lower (0.889 MoM) but this did not quite reach significance (p=0.064). The corresponding median MoM values for PAPP-A were 1.00 MoM for the controls, 0.49 MoM for trisomy 21 and 0.16 MoM for trisomy 18. The median MoM values for free beta-hCG were 1.00 MoM for the controls, 2.05 MoM for trisomy 21 and 0.38 MoM for trisomy 18. In the control group there was a small but significant correlation of PIGF with free beta-hCG (r=+0.1024) and PAPP-A (r=+0.2288). In the trisomy 18 group there was a significant association between PIGF and free beta-hCG (r=+0.2629) but not with PAPP-A (r=+0.0038). In the trisomy 21 group there was a small but significant association with PAPP-A (r=+0.1028) but not with free beta-hCG (r=+0.0339). The separation of affected and unaffected pregnancies in maternal serum PIGF is small, and therefore it is unlikely that measurement of PIGF would improve screening for these abnormalities provided by the combination of fetal nuchal translucency and maternal serum PAPP-A and free beta-hCG.

Adult↗
PubMed2003

Trisomy 8 mosaicism: selective growth advantage of normal cells vs. growth disadvantage of trisomy 8 cells.

A fetus with trisomy 8 mosaicism was identified prenatally due to an abnormal maternal serum triple screen. Tissue samples were taken at birth to determine the level of trisomy 8 mosaicism found within embryonic and extra-embryonic tissues, rates of cell division for the two cell lines, and the effect of mosaicism on the phenotype. The level of trisomy 8 cells in blood and fibroblasts was higher than in placental tissue. Cell cycle kinetics, by incorporation of bromodeoxyuridine for 48 hr, was not significantly different between the trisomy 8 and normal cells for blood or amnion. Fluorescent in situ hybridization (FISH) using centromeric probe for chromosome 8 showed significantly more trisomy 8 in interphase vs. metaphase in lymphoblasts, umbilical cord fibroblasts, and chorion. The loss of trisomy 8 cells is not due to anaphase lag, as determined by micronuclei analysis. The similarity of cell cycle kinetics between trisomy 8 cells and normal diploid cells suggests some trisomy 8 cells are exiting the cell cycle prematurely. This growth disadvantage of trisomy 8 cells results in the appearance of growth advantage for diploid cells.

Amnion↗
PubMed1989

Altered placental morphology associated with murine trisomy 16 and murine trisomy 19.

The morphology of placentas from trisomy 16 and trisomy 19 mouse conceptuses aged 12 to 18 gestational days was studied at the light microscopic level. Comparisons were made with placentas from normal littermate animals. Trisomy 16 placentas showed marked changes from normal: 1) the junctional zone showed little indication of normal morphologic differentiation throughout gestation; 2) clusters of germinal trophoblast cells persisted in the labyrinth throughout gestation, whereas these cells disappeared by gestational day 16 in the normal littermate placentas; 3) the labyrinth was reduced in size in the trisomic placentas, and the differentiation of the interhemal membranes was delayed. The size of the labyrinths from trisomy 19 placentas appeared to be decreased, but otherwise the placentas appeared to have normal morphology. These observations and others from the literature show that placental development is affected by the presence of a trisomic genome, and that different trisomies influence the development of the placenta differently. For trisomy 16, we propose that the striking changes of the junctional zone may be associated with the trisomy 16-related gene dosage effect for alpha- and beta-interferon cell surface receptors. Because of the homology for this and other genes on mouse chromosome 16 with genes on human chromosome 21, findings related to the altered development of the trisomy 16 mouse may be relevant to understanding some of the phenotypic variations associated with human trisomy 21, the Down syndrome.

Animals↗
PubMed1977

[Chromosome 8 : complete trisomy and segmental trisomies].

The phenotypic effects of trisomy of various segments of chromosome 8 have been recognized through the analysis of twelve different patients: five mosaic cases of trisomy 8, one case of trisomy for the short arm and the proximal segment of the long arm, two cases of trisomy for a portion of the short arm, and four cases of trisomy for the terminal segment of the long arm. Analysis of the data from the literature and of these personal observations allows the definition of three syndromes: trisomy 8, trisomy 8p and 8q proximal, and trisomy 8q terminal. Three clinical signs are common to the three syndromes: vertebral anomalies, depression of the mesosternum, and bulging of the forehead. This suggests that different segments of chromosome 8 carry genes affecting osseous growth. Trisomy 8p causes, in addition to severe mental deficiency, a thick nose, a large mouth, and microcephaly. Other clinical signs can be assigned to three groups corresponding to the short arm, the proximal part, and the distal part of the long arm.

Abnormalities, Multiple↗
PubMed1998

Trisomy 16 and trisomy 16 Mosaicism: a review.

A review of all prenatal and postnatal diagnoses of trisomy 16 and trisomy 16 mosaicism was carried out in the context of the current understanding of confined placental mosaicism and uniparental disomy (UPD). The prenatal detection of trisomy 16 cells is associated with a high probability of fetal death, preterm delivery, intrauterine growth retardation, and fetal anomalies. Birth defects were typical of those seen in nonmosaic partial duplications of chromosome 16. Surprisingly, anomalies were sometimes limited to a single organ and included some relatively common isolated defects such as a ventricular septal defect, hypospadias, imperforate anus, inguinal hernia, and clubfoot. The risk for abnormality appeared to be higher in those pregnancies in which trisomy 16 cells were identified in amniotic fluid compared to the detection in chorionic villi samples. Contrary to nonmosaic trisomy 16 with an excess of males, mosaic trisomy 16 shows an excess of female karyotypes. Following the prenatal detection of trisomy 16 cells, aneuploid cells are almost never found in fetal or neonatal lymphocytes. Studies on fibroblasts also often fail to confirm the presence of the abnormal cell line even in cases in which multiple anomalies are present. It is likely that trisomy 16 cells are sometimes present in the early developing embryo even though subsequent cytogenetic studies on fetal or neonatal tissues may not detect any aneuploid cells. UPD can be excluded as a mechanism for those anomalies that are common to mosaic trisomy 16 and nonmosaic partial duplications. The term "occult mosaicism" is suggested to describe the situation in which the presence of an abnormal cell line is suspected on the basis of clinical data but unproven by laboratory analysis.

Amniocentesis↗
PubMed1994

Natural history of trisomy 18 and trisomy 13: I. Growth, physical assessment, medical histories, survival, and recurrence risk.

The natural history of trisomy 18 and trisomy 13 was investigated using data derived from parent questionnaires and medical records from 98 families with an index case of trisomy 18 and 32 families with an index case of trisomy 13. Data are presented on pregnancy, delivery, survival, medical complications, immunizations, growth, cause of death, cytogenetics, and recurrence risk. Half of the trisomy 18 babies were delivered by C-section. Fetal distress was a factor in half, and the only reason in a third of C-section deliveries. One minute Apgar scores were significantly lower in C-section and breech deliveries. There were more small for gestational age babies than in the general population, but most of the low birth weight newborns were small for gestational age, unlike the general population. Survival in this group of children was better than in other studies due to ascertainment bias. There were more girls than boys at all ages for both conditions, and the sex ratio decreased with time. Growth curves for length, weight, head circumference, and weight vs height are provided. Long-term survival did not appear to be due to mosaicism. We found no adverse reactions attributable to immunizations. At age 1 year there was an average of approximately 2 operations per living child. We report the second case of successful major cardiac surgery in a trisomy 18 child. Almost 70% of deaths were attributed to cardiopulmonary arrest. The sibling recurrence risk for trisomy 18 or trisomy 13 was 0.55%.

Abnormalities, Multiple↗
PubMed2003

Trisomy 13 and trisomy 18 in a defined population: epidemiological, genetic and prenatal observations.

OBJECTIVES: To establish precise incidence figures for trisomy 13 and trisomy 18 in the former Trent region, to identify current prenatal diagnostic practice, and to assess the potential impact of the introduction of recently devised prenatal diagnostic practices. METHODS: An audit of all cases of trisomy 13 and trisomy 18 ascertained through the records of the Trent Congenital Anomalies Register and the Trent Regional Cytogenetic Laboratories. RESULTS: Forty-four cases of trisomy 13 and 88 cases of trisomy 18 were ascertained. Advanced maternal age effects were observed. Of all cases, 64% were first detected through chromosomal analysis initiated because of abnormalities noted on fetal anomaly scanning in the second trimester, whereas only 3% of cases were detected through the serum-screening programme currently offered for Down syndrome. In 11% of cases, the diagnosis was first suspected after birth. Twelve percent of couples chose to continue pregnancy following chromosomal confirmation of a suspected diagnosis. CONCLUSION: The introduction of a highly sensitive prenatal diagnostic screening programme would have a major impact on the timing and proportions of all trisomy 13 and 18 cases diagnosed in pregnancy as gauged by current practice. It is important that health professionals involved in prenatal counselling be aware that, as with Down syndrome and anencephaly, around 12% of prospective parents of a child with trisomy 13 or 18 choose to continue rather than terminate the pregnancy.

Adult↗
PubMed1998

Studies of non-disjunction in trisomies 2, 7, 15, and 22: does the parental origin of trisomy influence placental morphology?

Recently, there have been several molecular studies of trisomic fetuses and liveborns which have examined the parent and meiotic stage of origin of nondisjunction. However, little is known about the possible phenotypic effects of the origin of trisomy. For trisomic spontaneous abortions, no distinct phenotype has been described, although some have been reported to have features, such as trophoblastic hyperplasia, similar to hydatidiform moles. In the present report, we describe molecular and histological studies of spontaneous abortions with trisomies 2, 7, 15, or 22, conditions occasionally linked to trophoblastic hyperplasia. Our results provide strong evidence for chromosome specific mechanisms of nondisjunction, with trisomy 2 having a high frequency of paternally derived cases and trisomy 7 typically originating postzygotically. In studies correlating parental origin of trisomy with phenotype, we found no difference in the proportion of cases with trophoblastic hyperplasia, fetal tissue, nucleated red blood cells, or hydropic villi among paternally or maternally derived trisomies 2, 7, 15, or 22. However, paternally derived trisomies tended to abort earlier than maternally derived trisomies. This suggests that parental origin might affect the developmental stage at which abortion occurs but not other features of placental phenotype.

Abortion, Spontaneous↗
PubMed1987

Genesis and systematization of cardiovascular anomalies and analysis of skeletal malformations in murine trisomy 16 and 19. Two animal models for human trisomies.

On account of genetic homologies, trisomy 16 in the mouse is generally regarded as a direct animal model of Down's syndrome. Mouse trisomy 19, on the other hand, can be seen as a general model of human trisomies. A detailed evaluation of the cardiovascular system and skeleton in 109 fetuses with trisomy 16 and 422 balanced siblings was carried out in order to systematize the cardiovascular anomalies and the pathogenetic mechanisms responsible for their formation according to (1) general retardation, (2) genetically determined impairment of neural-crest cell migration, and (3) direct gene action on organogenesis. Skeletal malformations in the form of a rib-vertebra syndrome encountered in Ts 16 are described here for the first time. In 108 fetuses and 219 neonates resulting from cross-breeding to induce trisomy 19, we found no significant increase in the frequency of the foregoing anomalies. These results are discussed with regard to a chromosome-specific genetic influence as opposed to a general effect of chromosome imbalance. The specificity of the Ts16 syndrome is compared with that of individual organ anomalies as can be induced by teratogenic agents. Our investigation shows that specific malformation patterns of a particular type can be produced by a variety of methods. However, the overall patterns of the two syndromes are highly chromosome-specific. On detailed examination, the malformation pattern of mouse trisomy 16 shows significant similarities with that of human trisomy 21.

Animals↗
PubMed1990

Ultrasonographic detection of the second-trimester fetus with trisomy 18 and trisomy 21.

Biparietal diameter/femur length ratio and nuchal thickness were found to be sensitive indicators for the prenatal detection of trisomy 18 and trisomy 21. A biparietal diameter/femur length ratio greater than 1.5 SD above the control mean correctly identified 5 of 11 (46%) fetuses with trisomy 21 and 3 of 4 (75%) fetuses with trisomy 18. Nuchal thickening (6 mm or more) correctly identified 5 of 12 (41%) fetuses with trisomy 21 and 2 of 4 (50%) fetuses with trisomy 18. The sensitivity and specificity of the biparietal diameter/femur length ratio in detecting either aneuploidy was 53% and 93%, respectively, whereas a thickened nuchal fold had a sensitivity of 44% and a specificity of 100%. The combined use of the two ultrasonographic measurements had an overall sensitivity of 81% and a specificity of 93%. Prospective ascertainment of these two trisomies appears warranted in low-risk populations.

Chromosome Aberrations↗
PubMed1988

Trisomy 18 score: a rapid, reliable diagnostic test for trisomy 18.

We developed a bedside scoring system for diagnosis of trisomy 18 in the immediate neonatal period. Points are assigned for the presence of features known to occur in trisomy 18: five points for the presence of features previously reported in 50% or more of affected infants; three points for features reported to occur in between 10% and 50% of affected individuals; and one point for features known to occur in less than 10% of infants with the disorder. Using the scoring system, we evaluated two cohorts of patients: those in whom a diagnosis of trisomy 18 was previously established (retrospective group) and those in whom the diagnosis was suspected but not yet proved (prospective group). The average score in the retrospective series (n = 25) was 96.7, and no patient scored less than 70. Twenty-two patients were evaluated prospectively; in all cases the presence or absence of trisomy 18 was correctly predicted. The average score in the 11 patients without trisomy 18 was 41.4, and all patients scored 60 or less. In the 11 patients confirmed to have trisomy 18, the average score was 94.3, with a range of 70 to 113. This scoring system is an accurate, reproducible method for predicting trisomy 18 in neonates with multiple congenital malformations.

Chromosome Aberrations↗