Cytogenetics of pregnancy wastage

Cytogenetic Studies of 608 Couples with Recurrent Spontaneous Abortions in Northeastern Iran

Background & Objective:

One of the major genetic causes of recurrent spontaneous abortions is parental chromosomal abnormalities. The objectives of the study were to determine, compare and analyze the incidence and distribution of chromosomal abnormalities in couples with recurrent miscarriages from Northeastern Iran.

Methods:

This study was conducted at Ghaem Hospital, Mashhad, Iran. We evaluated karyotype results of 608 couples with history of recurrent spontaneous abortion. The standard method was used for culturing peripheral venous blood lymphocytes.

Results:

Chromosome aberrations were detected in 43 patients (3.54%), including 25 females and 18 males. Structural chromosomal abnormality was detected in 40 cases, including balanced translocations (25 cases), robertsonian translocations (4 cases), inversions (10 cases) and numerical chromosome aberrations (3 cases). Polymorphic variants were observed in 22 individuals.

Conclusion:

The frequency of chromosomal abnormalities in couples with Recurrent Spontaneous Abortion (RSA) in our study is 3.54%. Reciprocal translocation, pericentric inversions, robertsonian translocations, and numerical abnormality observed among couples who had experienced recurrent spontaneous abortions and that these couples might benefit from cytogenetic analysis.

Chromosomal Aberrations in 224 Couples with Recurrent Pregnancy Loss

Background

Recurrent pregnancy loss (RPL) is a major reproductive health issue, affecting 2%-5% of couples. Genetic factors, mainly chromosomal abnormalities, are the most common cause of early miscarriage accounting for 50%-60% of first trimester abortion.

Aim

To estimate the prevalence and nature of chromosomal anomalies in couples with recurrent miscarriage.

Patients and Methods

This study included 224 couples with a history of 2 or more abortions. Both partners were karyotyped as part of the primary investigation. Cytogenetic analysis was carried out using the standard method.

Results

A total of 224 couples with a history of two or more recurrent abortions were enrolled in this study. Chromosomal abnormalities were detected in 26 couples (11.6%) and 28 individuals (6.25%). We found a structural chromosome abnormality in 17/28 patients (60.7%); 12 patients had a reciprocal translocation (42.9%) including one patient with an additional inversion of the Y chromosome, 4 (14.3%) had a Robertsonian translocation, and one patient (3.6%) carried a paracentric inversion of chromosome 2. Numerical chromosome aberrations were detected in 5 patients; three patients (10.7%) with sex chromosome abnormalities and two (7.1%) with a marker chromosome. Six patients (21.4%) showed a heteromorphic variant involving chromosome 9.

Conclusion

The prevalence of chromosomal abnormalities in couples with RPL is within the range reported worldwide. Cytogenetic analysis should become an integral part of the investigations of couples with at least two pregnancy losses of undetermined etiology.

Association between hereditary predisposition to common cancers and congenital multimalformations

In a previous article we reported that mutations favoring cancer at adulthood seemed to improve fertility and limit miscarriages. Because spontaneous abortion may result from anomalies in embryo, we questioned if an increased frequency of congenital malformation could be evidenced among cancer-prone families. Oncogenetics database (≈193 000 members) of the comprehensive cancer center Jean Perrin was crossed with regional registry of congenital malformations (≈10 000). Among children born between 1986 and 2011, 176 children with malformation matched in both databases. In breast/ovaries cancer-prone families, the risk for malformations was multiplied by 2.4 [1.2-4.5] in case of a BRCA1 mutation. Frequencies of malformation in BRCA2 and MMR mutated families were similar to families without a cancer syndrome. In comparison to malformations concerning a unique anatomical system, multimalformations were significantly more frequent in case of BRCA or MMR mutations: compared to families without cancer syndrome, the risk of multimalformations was multiplied by 4.1 [0.8-21.7] for cancer-prone families but with no known deleterious mutation, by 6.9 [1.2-38.6] in families with a known mutation but an unknown parental mutational status and by 10.4 [2.3-46.0] when one parent carried the familial mutation. No association with the type of anatomical system was found, nor with multiple births. These results suggest that BRCA and MMR genes play an important role in human embryogenesis and that if their function is lowered because of heterozygote mutations, congenital malformations are either more likely (BRCA1 mutations) and/or more susceptible to concern several anatomical systems.

Unveiling the tale of the tail: an illustration of spinal dysraphisms

Spinal dysraphism is an umbrella term describing herniation of meninges or neural elements through defective neural arch. They can be broadly categorized into open and closed types. MRI is the investigation of choice to study neural abnormalities and to assess the severity of hydrocephalus and Chiari malformation. Knowledge of the embryology of these disorders is valuable in correctly identifying the type of dysraphism. The aim of surgery is untethering and dural reconstruction. Accurate depiction of the abnormal anatomy in cases of spinal dysraphism is of utmost importance for surgical management of these patients. MRI makes this possible due to its excellent soft tissue contrast resolution and multiplanar capability, allowing the radiologist to evaluate the intricate details in small pediatric spinal structures. Imaging enlightens the surgeons about the status of spinal cord and other associated abnormalities and helps detect re-tethering in operated cases. Besides, antenatal surgery to repair myelomeningoceles has made detection of open dysraphisms on fetal MRI and antenatal ultrasound critical. The purpose of this review is to describe the development of spine, illustrate the myriad imaging features of open and closed spinal dysraphisms, and enlist the reporting points the operating surgeon seeks from the radiologist.

Description of cytogenetic abnormalities and the pregnancy outcomes of couples with recurrent pregnancy loss in a tertiary-care center in Saudi Arabia

Objectives:

To determine the prevalence of chromosomal abnormalities in couples with recurrent pregnancy loss (RPL), to determine other factors that may be associated with the chromosomal abnormalities, and to assess the outcomes of couples who had undergone multidisciplinary interventions according to associated etiological factors.

Methods:

This retrospective cohort study involved 1074 couples who attended RPL clinic during an 11-year period from January 2006 to December 2016 at a single center, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia. All of the couples had undergone complete RPL evaluations and were closely monitored and managed during pregnancy.

Results:

Out of the 1074 couples, 77 (7.2%) carried some form of chromosomal abnormality, and the female (48, 62.3%) patients were affected more frequently than the male (29, 37.3%) patients. Out of the 77 cases with chromosomal abnormalities, 46.8% had reciprocal translocations, 10.3% had Robertsonian translocations, and 3.9% had complex structural abnormalities. Inversions had occurred in 14.3% and chromosomal additions had occurred in 2.6% of the patients. Isolated chromosomal abnormalities were detected in 25 out of 77 (32.5%) couples. The couples were closely followed, and 67% of the subsequent pregnancies resulted in live births.

Conclusion:

This study’s findings provide an insight into the prevalence of chromosomal abnormalities in couples with RPL in our region and the factors that may be associated with RPL. This information will help to ensure the required resources are provided to care for these patients.

Tris(1,3-dichloro-2-propyl) Phosphate Exposure During the Early-Blastula Stage Alters the Normal Trajectory of Zebrafish Embryogenesis

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is an organophosphate flame retardant used around the world. Within zebrafish, we previously showed that initiation of TDCIPP exposure during cleavage (0.75 h post-fertilization, hpf) results in epiboly disruption at 6 hpf, leading to dorsalized embryos by 24 hpf, a phenotype that mimics the effects of dorsomorphin (DMP), a bone morphogenetic protein (BMP) antagonist that dorsalizes embryos in the absence of epiboly defects. The objective of this study was to (1) investigate the role of BMP signaling in TDCIPP-induced toxicity during early embryogenesis, (2) identify other pathways and processes targeted by TDCIPP, and (3) characterize the downstream impacts of early developmental defects. Using zebrafish as a model, we first identified a sensitive window for TDCIPP-induced effects following exposure initiation at 0.75 hpf. We then investigated the effects of TDCIPP on the transcriptome during the first 24 h of development using mRNA sequencing and amplicon sequencing. Finally, we relied on whole-mount immunohistochemistry, dye-based labeling, and morphological assessments to study abnormalities later in embryonic development. Overall, our data suggest that the initiation of TDCIPP exposure during early blastula alters the normal trajectory of early embryogenesis by inducing gastrulation defects and aberrant germ-layer formation, leading to abnormal tissue and organ development within the embryo.

The cumulative dose of gonadotropins used for controlled ovarian stimulation does not influence the odds of embryonic aneuploidy in patients with normal ovarian response

OBJECTIVE

Controlled ovarian hyperstimulation (COH) promotes multifollicular growth, increasing the chance of obtaining euploid embryos that will successfully implant. Whether aneuploidy is increased from COH with exogenous gonadotropins interfering with natural selection of dominant follicles is a concern. This study evaluates the association between gonadotropin exposure and aneuploidy.

METHODS

This is a retrospective cohort study of 828 patients that underwent 1122 IVF cycles involving controlled ovarian stimulation and trophectoderm biopsy for preimplantation genetic screening (PGS), from 2010 to 2015. Polymerase chain reaction (PCR) was used to assess aneuploidy. Kruskal-Wallis tests and logistic regression with generalized estimating equations (GEEs) were used for data analysis.

RESULTS

Overall, after controlling for patient age, ovarian reserve, stimulation protocol, days of stimulation, and diagnoses, there was no significant association between cumulative gonadotropin (GND) dose and the odds of aneuploidy (adjusted OR = 1.049, p = 0.232). Similarly, in cycles where patients did not require COH beyond cycle day 12, there was no significant association between cumulative gonadotropin dose and the odds of aneuploidy (adjusted OR = 0.909, p = 0.148). However, in cases where patients were stimulated past cycle day 12, there was a significant increase in the odds of aneuploidy (adjusted OR = 1.20, 95% CI 1.125-1.282, p < 0.0001) with increasing cumulative gonadotropin dose, with a small effect size (Cohen's d = 0.10, 95% CI 0.08-0.12). In this cohort, there was a 16.4% increase in the odds of aneuploidy for each 1000-u increase in cumulative GND exposure (adjusted OR = 1.164, p = 0.002). When the analysis was restricted to low responders (peak estradiol <500 pg/mL or <4 mature follicles achieved; there was no significant association between gonadotropin dose and aneuploidy (adjusted OR = 1.12, 95% CI 0.982-1.28, p = 0.09), regardless of the duration of COH required to reach vaginal oocyte retrieval.

CONCLUSION

The degree of exposure to exogenous gonadotropins did not significantly modify the likelihood of aneuploidy in patients with a normal ovarian response to stimulation (not requiring COH beyond cycle day 12). Patients requiring prolonged COH were demonstrated to have elevated odds of aneuploidy with increasing cumulative gonadotropin dose. This finding may reflect an increased tendency towards oocyte and embryonic aneuploidy in patients with a diminished response to gonadotropin stimulation.

Aneusomy detection with Karyolite-Bac on Beads® is a cost-efficient and high throughput strategy in the molecular analyses of the early pregnancy conception losses

Background

Approximately 10–15 % of all clinically recognized pregnancies end in miscarriage, the majority of them occur during the first trimester, underlying the cause of the loss. Genetic analysis of fetal tissues has the potential to provide valuable information and is highly recommended in some cases. Around 3–4 years ago, the gold standard for the analysis was the GTG Kayrotype, is well known that around 50 % of the tissue samples received failed to grow in culture. Different molecular techniques are used to improve the quality and the specificity of the study, intending to circumvent the limits of the Karyotype.

Results

Karyolite-BoBs™ (KL-BoB™) assay is a recent bead-based suspension, low density array technology with consistent results, probed that is an efficient molecular method to detect aneusomies in early pregnancy losses. Fifty samples from abortions were analyzed in order to probe and give more information about the methodology and analyze if KL-BoBs™ is a good and cost-efficient strategy. We detected 32 % of chromosomal abnormalities, in some of the cases more than one aberration was identified, the array CGH validate the observations.

Conclusions

This molecular strategy is a cost-effective sensitive tool in the early pregnancy loss study.

New tools for embryo selection: comprehensive chromosome screening by array comparative genomic hybridization

The objective of this study was to evaluate the usefulness of comprehensive chromosome screening (CCS) using array comparative genomic hybridization (aCGH). The study included 1420 CCS cycles for recurrent miscarriage (n = 203); repetitive implantation failure (n = 188); severe male factor (n = 116); previous trisomic pregnancy (n = 33); and advanced maternal age (n = 880). CCS was performed in cycles with fresh oocytes and embryos (n = 774); mixed cycles with fresh and vitrified oocytes (n = 320); mixed cycles with fresh and vitrified day-2 embryos (n = 235); and mixed cycles with fresh and vitrified day-3 embryos (n = 91). Day-3 embryo biopsy was performed and analyzed by aCGH followed by day-5 embryo transfer. Consistent implantation (range: 40.5–54.2%) and pregnancy rates per transfer (range: 46.0–62.9%) were obtained for all the indications and independently of the origin of the oocytes or embryos. However, a lower delivery rate per cycle was achieved in women aged over 40 years (18.1%) due to the higher percentage of aneuploid embryos (85.3%) and lower number of cycles with at least one euploid embryo available per transfer (40.3%). We concluded that aneuploidy is one of the major factors which affect embryo implantation.

Epidemiologic tools to study the influence of environmental factors on fecundity and pregnancy-related outcomes

Adverse pregnancy outcomes entail a large health burden for the mother and offspring; a part of it might be avoided by better understanding the role of environmental factors in their etiology. Our aims were to review the assessment tools to characterize fecundity troubles and pregnancy-related outcomes in human populations and their sensitivity to environmental factors. For each outcome, we reviewed the possible study designs, main sources of bias, and their suggested cures. In terms of study design, for most pregnancy outcomes, cohorts with recruitment early during or even before pregnancy allow efficient characterization of pregnancy-related events, time-varying confounders, and in utero exposures that may impact birth outcomes and child health. Studies on congenital anomalies require specific designs, assessment of anomalies in medical pregnancy terminations, and, for congenital anomalies diagnosed postnatally, follow-up during several months after birth. Statistical analyses should take into account environmental exposures during the relevant time windows; survival models are an appropriate approach for fecundity, fetal loss, and gestational duration/preterm delivery. Analysis of gestational duration could distinguish pregnancies according to delivery induction (and possibly pregnancy-related conditions). In conclusion, careful design and analysis are required to better characterize environmental effects on human reproduction.

A comparative cytogenetic study of miscarriages after IVF and natural conception in women aged under and over 35 years

PURPOSE

To compare the frequency and the spectrum of karyotype abnormality in the first trimester miscarriages in women aged under and over 35 years, who conceived naturally (NC) and who conceived through in vitro fertilization (IVF).

METHODS

Comparative analysis of cytogenetic data obtained by karyotyping of miscarriages in patients who conceived naturally, and who conceived through IVF. Patients were subcategorized by their age: <35 years (NC, n = 173; IVF, n = 108) and ≥ 35 years (NC, n = 107; IVF, n = 111).

RESULTS

A total of 499 miscarriage karyotypes was analyzed. The spectrum and the relative proportions of different cytogenetic categories in karyotypically abnormal miscarriages differed neither between the NC and IVF patients aged <35 years, nor between the NC and IVF patients aged ≥ 35 years. In the patients aged <35 years, the incidence of abnormal miscarriage karyotype was lower in the IVF group (37.04 % vs 62.43%). In the patients aged ≥ 35 years, the incidence of miscarriages with cytogenetic pathology did not differ between the NC and the IVF group (75.70 % vs 58.56%). The lowest frequency of karyotypically abnormal miscarriages (29.82%) was detected in the young IVF-treated patients at <7 weeks of gestation.

CONCLUSIONS

IVF does not increase the risk of a pregnancy loss because of abnormal embryonic karyotype, nor does it increase the preponderance for any specific type of cytogenetic abnormality in both patients aged under and over 35 years. In young IVF-treated women early pregnancy loss is generally caused by non-cytogenetic factors. Identification of a cytogenetically normal spontaneous abortion is clinically significant and reinforces the importance of developing an appropriate diagnosis and treatment strategies for IVF patients in order to reduce the risk of euploid pregnancy loss.

Extreme methylation values of imprinted genes in human abortions and stillbirths

Imprinted genes play an important role in fetal and placental development. Using quantitative bisulfite pyrosequencing assays, we determined the DNA methylation levels at two paternally methylated (H19 and MEG3) and four maternally methylated (LIT1, NESP55, PEG3, and SNRPN) imprinted regions in fetal muscle samples from abortions and stillbirths. Two of 55 (4%) spontaneous abortions and 10 of 57 (18%) stillbirths displayed hypermethylation in multiple genes. Interestingly, none of 34 induced abortions had extreme methylation values in multiple genes. All but two abortions/stillbirths with multiple methylation abnormalities were male, indicating that the male embryo may be more susceptible to excess methylation. Hypermethylation of multiple imprinted genes is consistent with stochastic failures of the mechanism, which normally protects the hypomethylated allele from de novo methylation after fertilization. Two of six informative abortions/stillbirths with H19 hypermethylation revealed significant biallelic expression of the autocrine growth factor IGF2. In two other cases hypermethylation of MEG3 was associated with transcriptional down-regulation. We propose that primary epimutations resulting in inappropriate methylation and expression patterns of imprinted genes may contribute to both normal human variation and disease, in particular spontaneous pregnancy loss.

Canine and feline pregnancy loss due to viral and non-infectious causes: a review

Among the causes for pregnancy loss, viruses and non-infectious factors are among the most important. In both dogs and cats, research and clinical evidence provide proof that there is an increasing incidence of pregnancy loss associated with infectious diseases like herpesvirus, as well as the presence of toxicants or chemicals in the animal's diet and environment. Endocrine causes must be taken into consideration when dealing with pregnancy loss. This review will cover the most recent knowledge regarding viral and non-infectious of pregnancy losses in the dog and cat.

Aneuploidy involving chromosome 1 in failed-fertilized human oocytes is unrelated to maternal age

PURPOSE

To study whether maternal meiotic errors in failed-fertilized oocytes involving chromosome 1 occur at frequencies similar to those involving other autosomes, and whether their frequency is affected by maternal age.

METHODS

Using fluorescence in situ hybridization (FISH), frequencies of aneusomy and chromatid pre-division involving chromosomes 1, 16, 18, and 21 were determined for 273 failed-fertilized oocytes.

RESULTS

The aneuploidy rate for chromosome 1 was 15.8%, and was neither age-dependent nor significantly different from that for chromosomes 16, 18 or 21. Only chromosome 16 exhibited an age-dependent increase in aneusomy rates. The frequency of chromatid pre-division was lower for chromosome 1 than for chromosome 18 (11.9% vs. 25.4%; p = 0.01), but not different from that for chromosomes 16 or 21.

CONCLUSION

Aneuploidy involving chromosome 1 in failed-fertilized oocytes is unrelated to maternal age and occurs at a frequency similar to that for chromosomes 16, 18, and 21.

The cytogenetics of preimplantation human development: insights provided by traditional and novel techniques

Our understanding of the incidence and origin of chromosome abnormalities in human preimplantation embryos is very limited due to the necessary ethical constraints involved in studying such material and the limited data ultimately produced. Several studies have addressed this issue, however, using techniques such as interphase fluorescence in situ hybridisation, modified G-banding preparation and the use of single-cell comparative genomic hybridisation (CGH). This review discusses the use of these techniques in assessing chromosome abnormalities in this, the earliest of human developmental stages. In addition, the prospects for the clinical use of CGH are discussed.

Influence of paternal age on the risk of spontaneous abortion

The frequency of chromosomal anomalies in spermatozoa appears to increase with male age. Because these anomalies play a role in the etiology of spontaneous abortion, an influence of paternal age on risk of spontaneous abortion is plausible but not established. The aim was to characterize this influence in a prospective study among 5,121 California women, who as members of a prepaid health plan were interviewed in 1990 or 1991 when they were less than 13 weeks' pregnant and who were followed until the end of pregnancy. The risk of spontaneous abortion between weeks 6 and 20 of pregnancy was studied using a Cox model adjusted for maternal age. The adjusted hazard ratio of spontaneous abortion associated with paternal age of 35 years or more, compared with less than 35 years, was 1.27 (95% confidence interval: 1.00, 1.61), with no modification by maternal age. Among women aged less than 30 years, the hazard ratio of spontaneous abortion associated with paternal age of 35 years or more was 1.56 for first trimester spontaneous abortion and 0.87 for early second trimester spontaneous abortion (test of interaction, p = 0.25). In conclusion, the risk of spontaneous abortion increased with increasing paternal age, with a suggestion that the association is stronger for first trimester losses.

Aneuploidy study of human oocytes first polar body comparative genomic hybridization and metaphase II fluorescence in situ hybridization analysis

BACKGROUND

The object of this study was to determine the mechanisms that produce aneuploidy in oocytes and establish which chromosomes are more prone to aneuploidy.

METHODS

A total of 54 oocytes from 36 women were analysed. The whole chromosome complement of the first polar body (1PB) was analysed by comparative genomic hybridization (CGH), while the corresponding metaphase II (MII) oocyte was analysed by fluorescence in situ hybridization (FISH) to confirm the results.

RESULTS

Matched CGH-FISH results were obtained in 42 1PB-MII doublets, of which 37 (88.1%) showed reciprocal results. The aneuploidy rate was 57.1%. Two-thirds of the aneuploidy events were chromatid abnormalities. Interestingly, the chromosomes more frequently involved in aneuploidy were chromosomes 1, 4 and 22 followed by chromosome 16. In general, small chromosomes (those equal to or smaller in size than chromosome 13) were more prone to aneuploidy (chi2-test, P=0.07); 25% of the aneuploid doublets would have been misdiagnosed as normal using FISH with probes for nine-chromosomes.

CONCLUSIONS

The combination of two different techniques, CGH and FISH, for the study of 1PB and MII allowed the identification and confirmation of any numerical chromosome abnormality, as well as helping to determine the mechanisms involved in the genesis of maternal aneuploidy.

In vivo binding of active heat shock transcription factor 1 to human chromosome 9 heterochromatin during stress

Activation of the mammalian heat shock transcription factor (HSF)1 by stress is a multistep process resulting in the transcription of heat shock genes. Coincident with these events is the rapid and reversible redistribution of HSF1 to discrete nuclear structures termed HSF1 granules, whose function is still unknown. Key features are that the number of granules correlates with cell ploidy, suggesting the existence of a chromosomal target. Here we show that in humans, HSF1 granules localize to the 9q11-q12 heterochromatic region. Within this locus, HSF1 binds through direct DNA-protein interaction with a nucleosome-containing subclass of satellite III repeats. HSF1 granule formation only requires the DNA binding competence and the trimerization of the factor. This is the first example of a transcriptional activator that accumulates transiently and reversibly on a chromosome-specific heterochromatic locus.

Preimplantation genetic diagnosis in clinical practice

Preimplantation genetic diagnosis (PGD) represents an alternative to prenatal diagnosis and allows selection of unaffected IVF embryos for establishing pregnancies in couples at risk for transmitting a genetic disorder.

Cytogenetic analyses of culture failures by comparative genomic hybridisation (CGH)-Re-evaluation of chromosome aberration rates in early spontaneous abortions

Comparative genomic hybridisation (CGH) represents an alternative molecular-cytogenetic technique capable of detecting chromosomal imbalances by reverse fluorescence in situ hybridisation. As the technique uses genomic DNA for assessment it does not rely on metaphase chromosomes in the test material and thus circumvents technical problems associated with tissue culturing. In the present study, we applied CGH to identify chromosome anomalies in 60 spontaneous abortions of the first trimester, that had failed to grow in culture. In 57 out of 60 cases CGH analyses were successful. The overall aneuploidy rate detected was 72%. Trisomy was the predominant chromosome anomaly accounting for 68.0% of abnormal abortions, followed by triploidy (17.1%) and monosomy X (9.8%). An unbalanced structural rearrangement was found in one (2.4%) abortion. Most frequently involved in trisomies were chromosomes 16 (32.1%), 7 and 22 (10.7% each), 4, 13, 15, and 21 (7.2 % each). Three triploid cases and one complete mole were detected by microsatellite analysis as supplementary method. CGH data on culture failures were compared with data derived from 4693 successfully karyotyped first trimester spontaneous abortions, resulting in a chromosome aberration rate of 64.8%. The distribution of the different chromosome anomalies was similar with the exception of a higher rate of trisomies 7 and of XYY-triploidies in the culture failures. Based on our data we suggest that the genetic contribution to pregnancy loss is still underestimated. Investigating abortion tissues hitherto unassessed by conventional methods, we suggest that the contribution of chromosome aberrations to first trimester pregnancy loss is nearly 70%.

Highly conserved repetitive DNA sequences are present at human centromeres

Highly conserved repetitive DNA sequence clones, largely consisting of (GGAAT)n repeats, have been isolated from a human recombinant repetitive DNA library by high-stringency hybridization with rodent repetitive DNA. This sequence, the predominant repetitive sequence in human satellites II and III, is similar to the essential core DNA of the Saccharomyces cerevisiae centromere, centromere DNA element (CDE) III. In situ hybridization to human telophase and Drosophila polytene chromosomes shows localization of the (GGAAT)n sequence to centromeric regions. Hyperchromicity studies indicate that the (GGAAT)n sequence exhibits unusual hydrogen bonding properties. The purine-rich strand alone has the same thermal stability as the duplex. Hyperchromicity studies of synthetic DNA variants indicate that all sequences with the composition (AATGN)n exhibit this unusual thermal stability. DNA-mobility-shift assays indicate that specific HeLa-cell nuclear proteins recognize this sequence with a relative affinity greater than 10(5). The extreme evolutionary conservation of this DNA sequence, its centromeric location, its unusual hydrogen bonding properties, its high affinity for specific nuclear proteins, and its similarity to functional centromeres isolated from yeast suggest that this sequence may be a component of the functional human centromere.

Phenotypic expression of the first liveborn 68,XX triploid newborn

Images

Triple trisomy in a 17-week-old fetus

Autosomal trisomies account for the majority of chromosome abnormalities associated with spontaneous miscarriages. Occasionally, double autosomal trisomies are found to be present in abortuses. This report describes the second occurrence of triple trisomy associated with fetal demise.

Significance of structural chromosome aberrations in human sperm: analysis of induced aberrations

A significant increase in the incidence of structural chromosome anomalies has been observed in the sperm of patients treated with radio and/or chemotherapy for different types of cancer when analyzed by the interspecific fertilization of hamster eggs. The analysis of these aberrations shows that while in controls only 9.4% of structural abnormalities are of the stable type, in treated patients this figure increases to 39.3%, thus indicating that the anomalies have not been produced during the fertilization of the hamster egg. However, it is possible that part, or even most, of the breaks appear as a result of a reduced repair capacity of sperm chromosomes in the cytoplasm of the hamster egg.

Antenatal ultrasonographic diagnosis of trisomy 18 (Edwards syndrome)

A 35-yr-old G7P6A0 presented at 28 weeks of gestation with an acute polyhydramnios. On ultrasonographic examination the diagnosis of trisomy 18 in the fetus was suspected. This was confirmed by chromosome analysis of the cultured amniocytes. The value of a systematic ultrasonographic examination, especially in every abnormal pregnancy, is briefly discussed.

A cytogenetic study directly from chorionic villi of 140 spontaneous abortions

Spontaneous abortions were studied by analyzing chromosomes directly from chorionic villi. The frequency and the type of anomalies detected among 140 abortuses are in good agreement with those observed by others using conventional tissue cultures. Abnormal karyotypes were found in 48.6% of the cases. Trisomy predominated (66.2%), followed by polyploidy (22.1%), monosomy X (7.4%), and structural anomalies (4.4%). Among the trisomies, the most prevalent were of chromosome 22 (22.2%), 16 (22.2%), and 13 (9.5%). The relative frequencies of trisomies, monosomy X, and the different chromosomes involved in trisomies seem to differ between our study and those in which tissue cultures were analyzed. Our low frequency of 45,XO karyotypes and the shift to trisomies of chromosomes whose involvement increases steeply with maternal age are considered due to the approximately 3 year higher mean maternal age in our sample. The sex ratio (male to female) in chromosomally abnormal abortuses was 1.28, which is nearly identical to the 1.2 found in earlier studies. Surprisingly, in chromosomally normal abortions males were significantly outnumbered by females (sex ratio 0.76). Since maternal cell contamination cannot have influenced the sex ratio in our study, we consider it worthwhile to investigate whether failures associated with X inactivation are responsible for pregnancy wastage of some euploid female conceptuses. Knowledge of the karyotypes may serve as a prerequisite for the investigation of non-chromosomal genetic causes of pregnancy wastage.