Unusually long survival in a case of full triploidy of maternal origin

Extended survival of a premature infant with a postnatal diagnosis of complete triploidy

Triploidy is a common chromosomal abnormality that usually results in spontaneous abortion. Liveborn infants usually die within hours or days of birth. We present the case of a female infant born at 30 weeks and 5 days of gestation who received a late postnatal diagnosis of complete triploidy. She had severe intrauterine growth restriction and postnatal findings of multiple facial and limb anomalies. Genetic testing was sent shortly after birth, and the baby had an uneventful neonatal admission, requiring low-level respiratory and feeding support. Following a diagnosis of complete triploidy, she was transferred to a hospice and died on day 36 of life. There are currently 12 other reported cases of survival beyond 30 days. This case adds to the known cohort and highlights the importance of genetic testing in premature neonates with congenital anomalies in order to guide ceiling of care discussions and advocate for quality of life.

Genome-wide abnormalities in embryos: Origins and clinical consequences

Ploidy or genome-wide chromosomal anomalies such as triploidy, diploid/triploid mixoploidy, chimerism, and genome-wide uniparental disomy are the cause of molar pregnancies, embryonic lethality, and developmental disorders. While triploidy and genome-wide uniparental disomy can be ascribed to fertilization or meiotic errors, the mechanisms causing mixoploidy and chimerism remain shrouded in mystery. Different models have been proposed, but all remain hypothetical and controversial, are deduced from the developmental persistent genomic constitutions present in the sample studied and lack direct evidence. New single-cell genomic methodologies, such as single-cell genome-wide haplotyping, provide an extended view of the constitution of normal and abnormal embryos and have further pinpointed the existence of mixoploidy in cleavage-stage embryos. Based on those recent findings, we suggest that genome-wide anomalies, which persist in fetuses and patients, can for a large majority be explained by a noncanonical first zygotic cleavage event, during which maternal and paternal genomes in a single zygote, segregate to different blastomeres. This process, termed heterogoneic division, provides an overarching theoretical basis for the different presentations of mixoploidy and chimerism.

Restricted development of mouse triploid fetuses with disorganized expression of imprinted genes

Eukaryotic species commonly contain a diploid complement of chromosomes. The diploid state appears to be advantageous for mammals because it enables sexual reproduction and facilitates genetic recombination. Nonetheless, the effects of DNA ploidy on mammalian ontogeny have yet to be understood. The present study shows phenotypic features and expression patterns of imprinted genes in tripronucleate diandric and digynic triploid (DAT and DGT) mouse fetuses on embryonic day 10.5 (E10.5). Measurement of crown–rump length revealed that the length of DGT fetuses (1.87 ± 0.13 mm; mean ± standard error of the mean) was much smaller than that of diploid fetuses (4.81 ± 0.05 mm). However, no significant difference was observed in the crown–rump length between diploid and DAT fetuses (3.86 ± 0.43 mm). In DGT fetuses, the expression level of paternally expressed genes, Igf2, Dlk1, Ndn, and Peg3, remained significantly reduced and that of maternally expressed genes, Igf2r and Grb10, increased. Additionally, in DAT fetuses, the Igf2 mRNA expression level was approximately twice that in diploid fetuses, as expected. These results provide the first demonstration that imprinted genes in mouse triploid fetuses show distinctive expression patterns independent of the number of parental-origin haploid sets. These data suggest that both DNA ploidy and asymmetrical functions of parental genomes separately influence mammalian ontogeny.

Dosage regulation of the active X chromosome in human triploid cells

In mammals, dosage compensation is achieved by doubling expression of X-linked genes in both sexes, together with X inactivation in females. Up-regulation of the active X chromosome may be controlled by DNA sequence–based and/or epigenetic mechanisms that double the X output potentially in response to autosomal factor(s). To determine whether X expression is adjusted depending on ploidy, we used expression arrays to compare X-linked and autosomal gene expression in human triploid cells. While the average X:autosome expression ratio was about 1 in normal diploid cells, this ratio was lower (0.81–0.84) in triploid cells with one active X and higher (1.32–1.4) in triploid cells with two active X's. Thus, overall X-linked gene expression in triploid cells does not strictly respond to an autosomal factor, nor is it adjusted to achieve a perfect balance. The unbalanced X:autosome expression ratios that we observed could contribute to the abnormal phenotypes associated with triploidy. Absolute autosomal expression levels per gene copy were similar in triploid versus diploid cells, indicating no apparent global effect on autosomal expression. In triploid cells with two active X's our data support a basic doubling of X-linked gene expression. However, in triploid cells with a single active X, X-linked gene expression is adjusted upward presumably by an epigenetic mechanism that senses the ratio between the number of active X chromosomes and autosomal sets. Such a mechanism may act on a subset of genes whose expression dosage in relation to autosomal expression may be critical. Indeed, we found that there was a range of individual X-linked gene expression in relation to ploidy and that a small subset (∼7%) of genes had expression levels apparently proportional to the number of autosomal sets.

Many organisms have a single X chromosome in males and two in females, leading to a chromosome imbalance between autosomes and sex chromosomes and between the sexes. In mammals, this dosage imbalance is adjusted by doubling expression of X-linked genes in both sexes and by silencing one X chromosome in females. We used expression array analyses of human triploid cultures to test X chromosome expression in the presence of three sets of autosomes and address the question of an autosomal counting factor. We found that overall X-linked gene expression is not tripled in the presence of three sets of autosomes. However, in triploid cells with a single active X chromosome, its expression is adjusted upward presumably by an epigenetic mechanism that senses the active X/autosome ratio. Based on the range of individual gene expression we identified a subset of dosage-sensitive genes whose expression is apparently proportional to the ploidy. Our findings are important for understanding the regulation of the X chromosome and the role of ploidy in the balance of gene expression and associated phenotypes.

Abnormal X: autosome ratio, but normal X chromosome inactivation in human triploid cultures

BACKGROUND

X chromosome inactivation (XCI) is that aspect of mammalian dosage compensation that brings about equivalence of X-linked gene expression between females and males by inactivating one of the two X chromosomes (Xi) in normal female cells, leaving them with a single active X (Xa) as in male cells. In cells with more than two X's, but a diploid autosomal complement, all X's but one, Xa, are inactivated. This phenomenon is commonly thought to suggest 1) that normal development requires a ratio of one Xa per diploid autosomal set, and 2) that an early event in XCI is the marking of one X to be active, with remaining X's becoming inactivated by default.

RESULTS

Triploids provide a test of these ideas because the ratio of one Xa per diploid autosomal set cannot be achieved, yet this abnormal ratio should not necessarily affect the one-Xa choice mechanism for XCI. Previous studies of XCI patterns in murine triploids support the single-Xa model, but human triploids mostly have two-Xa cells, whether they are XXX or XXY. The XCI patterns we observe in fibroblast cultures from different XXX human triploids suggest that the two-Xa pattern of XCI is selected for, and may have resulted from rare segregation errors or Xi reactivation.

CONCLUSION

The initial X inactivation pattern in human triploids, therefore, is likely to resemble the pattern that predominates in murine triploids, i.e., a single Xa, with the remaining X's inactive. Furthermore, our studies of XIST RNA accumulation and promoter methylation suggest that the basic features of XCI are normal in triploids despite the abnormal X:autosome ratio.

Des andro- et parthénogénotes humains (môles hydatiformes et tératomes ovariens) au cancer

Genomic imprinting is a process that appeared in mammals. This phenomenon blocks the normal development of parthenogenic and androgenic conceptuses, that is to say benign ovarian teratomas and hydatidiform moles respectively. Pathological modifications of these conceptuses depend on whether the chromosomes come from the mother or father. These pathologies are associated with an accidental anomaly during gametogenesis and/or fertilizing. These reproductive anomalies are sporadic and some familial cases may exist suggesting a genetic control of such diseases. The human andro- and parthenogenetic conceptuses, but more frequently the moles, may be invasive (choriocarcinoma). An imbalance of the imprinting genes may initiate the deregulation of other genes, including oncogenes and anti-oncogenes, which can explain the cancerous modification. Immunological and environmental factors must be also considered (presence of the only paternal chromosomes in the choriocarcinoma). Numerous works on this subject are published and some recent important discoveries underline the roles of genes HOX, Tim P3, E-cad and p-16, and the recurrent chromosome anomalies 7q21+and 8p21- in the mole to choriocarcinoma processing. Although these phenomena are complex and heterogeneous, the andro- and parthenogenote conceptuses are particularly interesting models with which to understand developmental disorders and cancerous progression.

Parental and meiotic origin of triploidy in the embryonic and fetal periods

Triploidy is a common finding both in early spontaneous abortions and in the fetal period. Previous studies suggested that the majority of triploidy was the result of diandry, specifically dispermy. Molecular determination of parental origin in fetal triploids has shown that digyny accounts for the majority of triploids in the fetal period. The aim of this study was to determine the meiotic level at which the error leading to digynic triploidy occurs and to extend the molecular analysis of parental origin of triploidy into the embryonic period. Maternal age of digynic triploids was compared with that of the diandric cases. Using polymorphic pericentromeric markers, we have shown that the majority of digynic triploidy is the result of errors in the second meiotic division. Digyny accounted for the majority of triploids, even in the nonfetal cases. Diandry predominated in a subset of the non-fetal cases in which embryos were not present and in which the placental findings of partial hydatidiform mole (PHM) were encountered. Maternal age differed between the digynic and diandric groups only for the non-fetal cases; this was attributed to differences in ascertainment.

Digynic triploid infant surviving for 46 days

We report on a triploid infant who survived for 46 days. She had severe intrauterine growth retardation, relative macrocephaly, and a small, noncystic placenta, which are manifestations compatible with type II phenotype. Cultured amniotic fluid cells, skin fibroblasts, cord blood, and peripheral blood lymphocytes all showed a nonmosaic 69,XXX karyotype. Analysis of chromosomal heteromorphisms and microsatellite DNA polymorphisms in the infant and her parents indicated that the extra haploid set in the infant resulted from nondisjunction at maternal second meiosis. Postzygotic, mitotic nondisjunction was ruled out because of the presence of both homozygous and heterozygous markers of maternal origin. A search of the literature demonstrated five triploid infants, including the girl we described, who survived 4 weeks or more, and the parental origin of whose triploidy was studied: four were digynic and one was diandric. These findings support the notion that type II triploids are digynic in parental origin and that they survive longer than type I, diandric triploids.

Placental pathology of triploidy

Triploidy is a common chromosome abnormality in spontaneous abortions. Previous studies of spontaneous abortions have suggested that approximately 85% of triploid abortuses show the placental changes of partial hydatidiform mole (PHM) and that this appearance was associated, possibly attributable, to paternal origin of the extra haploid set of chromosomes. More recent work, however, has shown that most triploidy is the result of digyny--the extra set of chromosomes originating from the mother. Given the association of PHM with diandry, these results would appear to be at odds with the results of previous studies of placental morphology in triploids. The authors reviewed the placental pathology of all cases of triploidy examined at their institution over a 2-year period and established that PHM occurs in a minority of triploid conceptuses. These results support the findings of studies showing that digyny is the most common origin of triploidy.

The cleavage rate of digynic triploid mouse embryos during the preimplantation period

Triploidy is a lethal condition in mammals, with most dying at some stage between implantation and term. In humans, however, a very small proportion of triploids are liveborn but display a wide range of congenital abnormalities. In particular, the placentas of human diandric triploid embryos consistently display "partial" hydatidiform molar degeneration, while those of digynic triploids generally do not show these histopathological features. In mice, the postimplantation development of diandric and digynic triploid embryos also differs. While both classes are capable of developing to the forelimb bud stage, no specific degenerative features of their placentas have been reported. Diandric triploid mouse embryos are morphologically normal while digynic triploid mouse embryos consistently display neural tube and occasionally cardiac abnormalities. Previously it was shown that the preimplantation development of micromanipulated diandric triploid mouse embryos was similar to developmentally matched diploid control embryos. In this study, the preimplantation development of micromanipulated digynic triploid mouse embryos is analysed and compared with that of diandric triploid mouse embryos in order to determine whether there is any difference in cleavage rate between these two classes of triploids. Standard micromanipulatory procedures were used to insert a female or a male pronucleus into a recipient diploid 1-cell stage embryo. The karyoplast was fused to the cytoplasm of the embryo by electrofusion. These tripronucleate 1-cell stage embryos were then transferred to pseudopregnant recipients and, at specific times after the HCG injection to induce ovulation, the embryos were recovered and total cell counts made. These results were plotted and regression lines drawn.(ABSTRACT TRUNCATED AT 250 WORDS)

A case of full triploidy (69,XXX) of paternal origin with unusually long survival time

Triploidy is a rare disorder in live-born children and these infants generally die within the first hours after birth. We report here on a girl with full triploidy and multiple malformations, who survived for 10 1/2 weeks. The extra set of haploid chromosomes was of paternal origin, as shown by chromosomal banding techniques.

A genetic review of complete and partial hydatidiform moles and nonmolar triploidy

Complete and partial hydatidiform moles are genetically aberrant conceptuses. Usually, complete moles have 46 chromosomes (diploidy), all of paternal origin. Most partial moles have 69 chromosomes (triploidy), including 23 of maternal origin and 46 of paternal origin. Triploidy that involves 23 paternal chromosomes and 46 maternal chromosomes is not associated with molar placental changes and, rarely, can result in a live-born infant with multiple birth defects. Herein we review the mechanisms of fertilization that may produce these unbalanced sets of parental chromosomes and the role of genomic imprinting as a possible explanation for these clinical conditions.

Full 69,XXY triploidy and sex-reversal: a further example of true hermaphrodism associated with multiple malformations

A 20-week gestational age fetus with full triploidy and multiple malformations is presented. In all examined lymphocytes, fibroblasts and chorionic villi, a 69,XXY karyotype was found. Autopsy examination revealed bilateral ovotestes but, no evidence of Müllerian derivatives.

Chromosome analysis of multipronuclear human oocytes after in vitro fertilization

Multipronuclear human eggs are frequent after in vitro fertilization. Their chromosome analysis can provide useful information. Before cleavage it can confirm the suspected polyploidy. Among the cleaved multipronuclear eggs it provides an estimation of the incidence of the possible return to diploidy. Ninety-four multipronuclear eggs were fixed at the first, second, or third cleavage according to the air-drying method of Tarkowski with or without colchicine exposure: 60 were successfully analysed. Twelve were stopped before cleavage (six without colchicine treatment and six with colchicine treatment). They were polyploid, confirming the cytological observation. Forty-eight eggs cleaved and were stopped by colchicine treatment and karyotyped. Seventeen eggs (35 per cent) had produced diploid embryos. Mosaicism was frequent (15 cases, 31 per cent). Triploidy was not frequent (8 eggs, 17 per cent). Haploidy constituted the remaining cases (8 eggs, 17 per cent). Our data indicate that the initial count of pronuclei is a reliable test. Multipronuclear one-cell oocytes were confirmed to be polyploid. Furthermore, the developmental capacity of the multipronuclear oocytes is variable. Most of them cleaved. However, many multipronuclear oocytes led to diploid cleaving eggs.

Triploidy syndrome in a liveborn female

We present the autopsy report of a liveborn triploid female, born after 36 weeks of gestation, who died at the age of 20 hours. External features were diagnostic: fetal hypoplasia, hypertelorism, microstomia, micro-and retrognathia, preauricular skin tag, low-set ears, and 3-4 syndactylia. All internal organs were hypoplastic. There were atrial and ventricular septal defects. Adrenals and kidneys were fused, the gallbladder was absent, and ovarian hilum cell were found to be hyperplastic. Triploidy, 69xxx, was confirmed cytogenetically. The placenta was hypoplastic and, microscopically, revealed a peculiar type of immaturity, so-called hydatidiform villous hypoplasia, findings which have not been previously reported. We suggest that the generalized fetal and placental hypoplasia and the severe hypoplasia of all internal organs are caused by a proliferative deficiency of the triploid cells. In addition, the nuclear DNA content was determined by cytophotometrically from placental stromal cells and was found to be about 50% above the normal diploid DNA value; i.e., a triploid DNA value was confirmed.

Embryonic development after microsurgical repair of polyspermic human zygotes

Correction of polyspermy through pronucleus extraction in the absence of membrane relaxants was applied to 25 polyspermic human zygotes. Nine zygotes survived the procedure, and seven cleaved normally (two of which were fixed for chromosome analysis); two proceeded to compact and one cavitated. Eighteen of the polyspermic zygotes (14 with three pronuclei and 4 with four pronuclei) were obtained from zona pellucida-intact oocytes, and seven (1 five-pronucleate 3 four-pronucleate, and 3 three-pronucleate) from previously zona-drilled oocytes. Survival and cleavage occurred in all groups except in four- and five-pronucleate zona-drilled zygotes. Criteria used to identify male pronuclei were (1) pronucleus-associated sperm tails, (2) increased pronucleus size, and (3) greater distance (relative to female pronuclei) from the second polar body. Sperm tails were never seen and pronucleus size usually was identical. Therefore, the third criterion was used, although its reliability should be further evaluated. Until complete pronucleus removal techniques and reliable pronucleus selection criteria are perfected, embryo replacement after polyspermy correction could result in aneuploidy and molar pregnancy.

Long survival in a 69,XXY triploid male

We report on an infant with a 69,XXY chromosome constitution who survived for 10 1/2 months; this is the longest survival reported with this condition to date. The infrequency of this disorder, data on natural history, and improved survival, possibly due to better management of respiratory illness and prematurity, are all factors worth noting in counseling on such rare conditions. Genotyping demonstrated the extra genome to be of maternal origin.

Diploid-triploid mosaicism: report of necropsy findings

This is the first report of necropsy findings associated with diploid-triploid mosaicism. The important pathological findings are presented and compared to those of pure triploidy and those noted in noninvasive studies of diploid-triploid mosaics. The clinical findings in this patient are compared with those of other reported cases.

A boy with complete triploidy and unusually long survival

A boy with complete triploidy and extensive external and internal congenital malformations who survived for almost seven months is presented. He was born after 31 weeks of gestation, was utterly small for gestational age and the delivery was induced because of intrauterine asphyxia. The infant had typical features of the complete triploidy syndrome. He did not develop mentally or motorically even to a normal neonatal level. Banding analysis of chromosomes and HLA-antigen typing of the patient and his parents suggested that the abnormal cell division had occurred during the oogenesis. The boy suffered a fatal Pneumocystis carinii infection, suggesting defective cellular immunity. In the vast majority of previously reported cases of complete triploidy the infant has died either before birth or within the first postnatal hours and except for four patients, all reported patients have died before the age of 2 months. Our patient illustrates the fact that with modern neonatal intensive care, infants with severe malformation syndromes can survive for longer periods than previously, but in the case of patients with the complete triploidy syndrome without developing mentally at all. The ethical problem of artificially prolonged survival in severely handicapped children is discussed.

Analysis of gross anatomical variations in human triploidy

Three cases of human triploidy were dissected in detail to determine whether or not there are any specific patterns of morphologic variation associated with this form of polyploidy. No specific constellations of anatomic variation were observed. However, each body did have a greater than normal number of variations among muscles that tend to be variable in the normal population. Two bodies showed a marked increase in the size of the thigh muscles, two bodies had eyeballs that were larger than normal, and two bodies had anomalous attachments of the extraocular muscles. The sample size is not large enough to draw any specific conclusions concerning the pathogenesis of these variations. However, the findings do suggest that careful examination of additional specimens will be of value in providing further information about the genotype/phenotype relationships in human triploidy.

Morphologic anomalies in triploid liveborn fetuses

Analysis of the morphologic features of 43 complete and 11 mosaic triploid infants delivered at or after 22 weeks of gestation revealed, in addition to well-delineated gross features, a number of new or previously little emphasized histopathologic features. These included testicular Leydig cell hyperplasia, increased levels of hematopoiesis, and ovarian, adrenal, and pulmonary hypoplasia. Some of these findings appeared to be linked to partial hydatidiform mole replacing the normal placenta, which was present in about 70 per cent of the triploid cases. It is important to recognize the breadth of the triploidy spectrum, which ranges from near normalcy to multisystem involvement, and to pay special attention to the placenta. The importance of correct morphologic diagnosis of triploidy is stressed in view of the fact that its occurrence apparently does not prejudice the future reproductive performance of the parents.

Human triploidy: relationship between parental origin of the additional haploid complement and development of partial hydatidiform mole

One hundred and six triploids were ascertained during a study of 1500 consecutive spontaneous abortions. The mechanism of origin of the additional haploid complement was investigated by comparing parental and foetal cytogenetic heteromorphisms and a histopathological examination of each triploid was done in a subsequent blind study. The mechanism of origin of the additional haploid complement was found to be highly correlated with the development of partial hydatidiform mole and with gestational age. All 51 paternally derived triploids in which a pathologic diagnosis could be made were partial moles, whereas only 3 of 15 maternally derived triploids on which a diagnosis could be made were molar. The mean gestational age of the paternally derived triploids was 122 days while that of the maternally derived triploids was only 74 days. It was suggested that the development of partial mole was primarily associated with the presence of two paternal haploid chromosome complements, the association with relatively long gestational ages being a secondary one consequent upon retention of the molar placentae for many weeks after foetal demise.

Genetic studies on hydatidiform moles. I. The origin of partial moles

A study was designed to investigate the genetic origin of hydatidiform moles. Fifty-nine specimens were obtained and, on a histological basis, separated into two entities: complete and partial. The study of the genetic origin of the 15 partial moles, using cytogenetic and biochemical markers, is described. All the partial moles examined cytogenetically were triploid. One had 71 chromosomes. The sex chromosome complements of seven cases were six XXY and one XXX. Origin by dispermy was possible in seven cases and was proven in four. With the use of biochemical markers a maternal contribution was identified in three cases, and the isoenzyme pattern suggested a trisomic state for at least one locus in four cases. The mechanism of origin of partial moles was compared with spontaneously aborted and liveborn triploids. All the patients were followed up for at least 9 months, and none required treatment for persistent trophoblastic activity.

Pathologic features of the eye in triploidy

Triploidy is a cytogenetic abnormality characterized by 69 chromosomes rather than the normal 46 in each cell. It is one of the most common chromosomal aberrations reported in early spontaneous abortion. Estimates are that 17-20% of chromosomally abnormal abortuses (early) are triploid. 1,2 Although the majority are stillborn, at least 25 liveborn triploidics have been reported. 3-9 All were premature and most died in the first 6 hours;the longest survival was 2 months. 4 By contrast, a diploid/triploid mosaic (mixed cell lines) individual may survive to adulthood. Although ocular lesions are one of the components of the triploidy syndrome, reports of histologic findings are comparatively rare. 1,3,6,10,11 This prompted us to study the ocular pathology in another case of triploidy. Our results confirm and extend those previously described and emphasize the pattern of ocular abnormalities in this disorder.

Preferential X inactivation in human placenta membranes: is the paternal X inactive in early embryonic development of female mammals?

In placenta membranes of newborn girls carrying electrophoretically distinguishable G6PD alleles, the maternally derived isozyme is expressed preferentially. This phenomenon cannot be explained by allelic differences in enzyme activity or by somatic selection directed against cells with particular G6PD phenotypes. Instead, it may be that in this tissue X inactivation is nonrandom. Preferential expression of the maternal X chromosome, as has been shown in marsupials and in extraembryonic membranes of rodents and now in man, may reflect the state of activity of the X chromosomes in the early stages of female embryonic development.