The incidence, origin, and etiology of aneuploidy

Prevalence, Morbidity, and Mortality of Men With Sex Chromosome Aneuploidy in the Million Veteran Program Cohort

Importance

The reported phenotypes of men with 47,XXY and 47,XYY syndromes include tall stature, multisystem comorbidities, and poor health-related quality of life (HRQOL). However, knowledge about these sex chromosome aneuploidy (SCA) conditions has been derived from studies in the less than 15% of patients who are clinically diagnosed and also lack diversity in age and genetic ancestry.

Objectives

To determine the prevalence of clinically diagnosed and undiagnosed X or Y chromosome aneuploidy among men enrolled in the Million Veteran Program (MVP); to describe military service metrics of men with SCAs; and to compare morbidity and mortality outcomes between men with SCA with and without a clinical diagnosis vs matched controls.

Design, Setting, and Participants

This cross-sectional study used a case-control recruitment design to select biological males enrolled in the MVP biobank in the US Veterans Administration health care system from 2011 to 2022. Cases were participants with 47,XXY syndrome or 47,XYY syndrome, matched 1:5 with controls based on sex, age, and genetic ancestry. Data were analyzed from January 2022 to December 2023.

Exposure

Genomic identification of an additional X or Y chromosome.

Main Outcomes and Measures

Outcomes of interest included prevalence of men with SCAs from genomic analysis; clinical SCA diagnosis; Charlson Comorbidity Index; rates of outpatient, inpatient, and emergency encounters per year; self-reported health outcomes; and standardized mortality ratio.

Results

Of 595 612 genotyped males in the MVP, 862 had an additional X chromosome (47,XXY) and 747 had an extra Y chromosome (47,XYY), with the highest prevalence among men with East Asian (47,XXY: 10 of 7313 participants; 47,XYY: 14 of 7313 participants) and European (47,XXY: 725 of 427 143 participants; 47,XYY: 625 of 427 143 participants) ancestry. Mean (SD) age at assessment was 61 (12) years, at which point 636 veterans (74.X%) with 47,XXY and 745 veterans (99%) with 47,XYY remained undiagnosed. Individuals with 47,XXY and 47,XYY had similar military service history, all-cause standardized mortality ratio, and age of death compared with matched controls. Individuals with SCA, compared with controls, had higher Charlson Comorbidity Index scores (47,XXY: mean [SD], 4.30 [2.72] vs controls: mean [SD], 3.90 [2.47]; 47,XYY: mean [SD], 4.45 [2.90] vs controls: mean [SD], 3.82 [2.50]) and health care utilization (eg, median [IQR] outpatient encounters per year: 47,XXY, 22.6 [11.8-37.8] vs controls, 16.8 [9.4-28]; 47,XYY: 21.4 [12.4-33.8] vs controls: 17.0 [9.4-28.2]), while several measures of HRQOL were lower (eg, mean [SD] self-reported physical function: 47,XXY: 34.2 [12] vs control mean [SD] 37.8 [12.8]; 47,XYY: 36.3 [11.6] vs control 37.9 [12.8]). Men with a clinical diagnosis of 47,XXY, compared with individuals without a clinical diagnosis, had higher health care utilization (eg, median [IQR] encounters per year: 26.6 [14.9-43.2] vs 22.2 [11.3-36.0]) but lower Charlson Comorbidity Index scores (mean [SD]: 3.7 [2.7] vs 4.5 [4.1]).

Conclusion and Relevance

In this case-control study of men with 47,XXY and 47,XYY syndromes, prevalence of SCA was comparable with estimates in the general population. While these men had successfully served in the military, they had higher morbidity and reported poorer HRQOL with aging. Longer longitudinal follow-up of this sample will be informative for clinical and patient-reported outcomes, the role of ancestry, and mortality statistics.

Prevalence, Morbidity, and Mortality of 1,609 Men with Sex Chromosome Aneuploidy: Results from the Diverse Million Veteran Program Cohort

Importance

The reported phenotypes of men with 47,XXY and 47,XYY syndromes include tall stature, multisystem comorbidities, and poor health-related quality of life (HRQoL). However, knowledge about these sex chromosome aneuploidy (SCA) conditions has been derived from studies in the <15% of patients who are clinically diagnosed and also lack diversity in age and genetic ancestry.

Objectives

Determine the prevalence of clinically diagnosed and undiagnosed X or Y chromosome aneuploidy among men enrolled in the Million Veteran Program (MVP); describe military service metrics of men with SCAs; compare morbidity and mortality outcomes between men with SCA with and without a clinical diagnosis to matched controls.

Design

Cross-sectional, case-control.

Setting

United States Veterans Administration Healthcare System.

Participants

Biologic males enrolled in the MVP biobank with genomic identification of an additional X or Y chromosome (cases); controls matched 1:5 on sex, age, and genetic ancestry.

Main Outcomes and Measures

Prevalence of men with SCAs from genomic analysis; clinical SCA diagnosis; Charlson Comorbidity Index (CCI); rates of outpatient, inpatient, and emergency encounters per year; self-reported health outcomes; standardized mortality ratio (SMR).

Results

An additional X or Y chromosome was present in 145 and 125 per 100,000 males in the MVP, respectively, with the highest prevalence among men with European and East Asian ancestry. At a mean age of 61±12 years, 74% of male veterans with 47,XXY and >99% with 47,XYY remained undiagnosed. Individuals with 47,XXY (n=862) and 47,XYY (n=747) had similar military service history, all-cause SMR, and age of death compared to matched controls. CCI and healthcare utilization were higher among individuals with SCA, while several measures of HRQoL were lower. Men with a clinical diagnosis of 47,XXY had higher healthcare utilization but lower comorbidity score compared to those undiagnosed.

Conclusion and Relevance

One in 370 males in the MVP cohort have SCA, a prevalence comparable to estimates in the general population. While these men have successfully served in the military, they have higher morbidity and report poorer HRQoL with aging. Longer longitudinal follow-up of this sample will be informative for clinical and patient-reported outcomes, the role of ancestry, and mortality statistics.

KEY POINTS

Comparable to the general population, approximately 1 in 370 male veterans have a sex chromosome aneuploidy, but most are undiagnosed.Men with X or Y chromosome aneuploidy successfully complete US miliary duty with similar service history compared to their 46,XY peers.Medical comorbidities and healthcare utilization metrics are higher in male veterans with 47,XXY and 47,XYY during aging, however life expectancy is similar to matched controls.

An improved deep convolutional neural network architecture for chromosome abnormality detection using hybrid optimization model

Chromosomes are thread-like structures located in the cell nucleus that contains the human body blueprint. Chromosome analysis is also known as karyotyping is the test taken to detect the abnormalities identified in the human chromosome. The two types of widely known chromosome abnormalities are structural and numerical abnormalities. Manual karyotyping is complex, time-consuming, and error-prone. To overcome these complexities, automated chromosome karyotype architecture is proposed using the deep convolutional neural network (DCNN) architecture. Training the DCNN architecture from scratch needs a huge dataset and to overcome this problem a generative adversarial networks is used to create adversarial samples that resemble the images in the actual dataset. The time-consuming hyperparameter tuning in the DCNN architecture is overcome using the hybrid moth-flame optimization integrated with the hill-climbing strategy (HMFOHC). The HMFOHC algorithm is mainly utilized in this article to minimize the huge number of parameters associated with the DCNN architecture. The efficiency of the proposed methodology is evaluated using two datasets namely the BioImLab chromosome dataset and hospital dataset. The proposed HMFOHC optimized DCNN architecture is mainly utilized for multiclass classification where it differentiates five numerical chromosome abnormalities, namely Trisomy 13, Trisomy 18, Trisomy 21, Trisomy XXY syndrome, and Monosomy X. The proposed model offers an accuracy, F1-score, and kappa coefficient value of 98.65%, 98.86%, and 0.9894, respectively. The results obtained show that the proposed model achieves higher classification accuracy when compared with the different state-of-art techniques such as deep learning, random forest, and CNN. The inference time of the proposed methodology is 12.5 s which is relatively lower than the state-of-art techniques. The proposed approach can help cytogenetics forensic experts make better decisions and save time by automating manual karyotyping.

On Mammalian Totipotency: What Is the Molecular Underpinning for the Totipotency of Zygote?

The mammalian zygote is described as a totipotent cell in the literature, but this characterization is elusive ignoring the molecular underpinnings. Totipotency can connote genetic totipotency, epigenetic totipotency, or the reprogramming capacity of a cell to epigenetic totipotency. Here, the implications of these concepts are discussed in the context of the properties of the zygote. Although genetically totipotent as any diploid somatic cell is, a zygote seems not totipotent transcriptionally, epigenetically, or functionally. Yet, a zygote may retain most of the key factors from its parental oocyte to reprogram an implanted differentiated genome or the zygote genome toward totipotency. This totipotent reprogramming process may extend to blastomeres in the two-cell-stage embryo. Thus, a revised alternative model of mammalian cellular totipotency is proposed, in which an epigenetically totipotent cell exists after the major embryonic genome activation and before the separation of the first two embryonic lineages.

High rates of aneuploidy, mosaicism and abnormal morphokinetic development in cases with low sperm concentration

Purpose

The aim of our study was to evaluate the impact of severe male infertility (SMF) on the chromosomal status of embryos and any possible correlation between chromosomal status and embryo morphokinetics in younger women using data obtained from comprehensive preimplantation genetic tests.

Methods

The trial was conducted in an ART and Reproductive Genetics Centre between 2011 and 2018. A total of 326 cycles in cases with SMF where the female partner’s age was ≤ 35 years were evaluated. SMF is defined as sperm concentration below 5 mil/ml (million per milliliter) and divided into three subgroups according to sperm concentrations: 1–5 mil/ml, < 1mil/ml and testicular sperm. The control group of 190 cycles had normal sperm parameters.

Results

Significantly lower chromosomal euploidy rates were found in the testicular sperm group compared with the normal sperm controls when the female age was ≤ 35 years. In SMF, statistically significantly affected chromosomes were 2, 10, 11, 17, 21 and sex chromosomes. The mosaicism and abnormal morphokinetic development rates were higher in the SMF group than in control group, and this difference was significant when testicular sperm was used.

Conclusion

Lower euploidy rates, higher mosaicism rates and a higher incidence of abnormal morphokinetic development were observed in cases with testicular sperm with female partners ≤ 35 years compared with normal sperm controls. These findings suggest that PGT-A may be advisable in severe male infertility cases. Furthermore, the correlation between morphokinetics and chromosomal status was greatly reduced or absent in these most severe forms of male infertility, thus the need for new morphokinetic models.

Electronic supplementary material

The online version of this article (10.1007/s10815-019-01673-w) contains supplementary material, which is available to authorized users.

Advanced paternal age does not affect embryo aneuploidy following blastocyst biopsy in egg donor cycles

PURPOSE

To study the impact of advanced paternal age on embryo aneuploidy.

METHODS

This is a multicenter international retrospective case series of couples undergoing assisted reproduction via in vitro fertilization using donor eggs to control for maternal factors and preimplantation genetic testing for aneuploidy via next-generation sequencing at Igenomix reproductive testing centers. The main outcome measure was the prevalence of embryo aneuploidy in egg donor cycles. Semen analysis data was retrieved for a small subset of the male patients.

RESULTS

Data from 1202 IVF/ICSI egg donor cycles using ejaculated sperm (total 6934 embryos) evaluated using PGT-A between January 2016 and April 2018 in a global population across all Igenomix centers were included. No significant association was identified between advancing paternal age and the prevalence of embryo aneuploidy overall and when analyzing for each chromosome. There was also no significant association between advancing paternal age and specific aneuploid conditions (monosomy, trisomy, partial deletion/duplication) for all chromosomes in the genome.

CONCLUSIONS

This is the largest study of its kind in an international patient population to evaluate the impact of advancing paternal age on embryo aneuploidy. We conclude there is no specific effect of paternal age on the prevalence of embryo aneuploidy in the context of embryo biopsies from egg donor cycles.

Semi-automated scoring of triple-probe FISH in human sperm using confocal microscopy

Structural and numerical sperm chromosomal aberrations result from abnormal meiosis and are directly linked to infertility. Any live births that arise from aneuploid conceptuses can result in syndromes such as Kleinfelter, Turners, XYY and Edwards. Multi-probe fluorescence in situ hybridization (FISH) is commonly used to study sperm aneuploidy, however manual FISH scoring in sperm samples is labor-intensive and introduces errors. Automated scoring methods are continuously evolving. One challenging aspect for optimizing automated sperm FISH scoring has been the overlap in excitation and emission of the fluorescent probes used to enumerate the chromosomes of interest. Our objective was to demonstrate the feasibility of combining confocal microscopy and spectral imaging with high-throughput methods for accurately measuring sperm aneuploidy. Our approach used confocal microscopy to analyze numerical chromosomal abnormalities in human sperm using enhanced slide preparation and rigorous semi-automated scoring methods. FISH for chromosomes X, Y, and 18 was conducted to determine sex chromosome disomy in sperm nuclei. Application of online spectral linear unmixing was used for effective separation of four fluorochromes while decreasing data acquisition time. Semi-automated image processing, segmentation, classification, and scoring were performed on 10 slides using custom image processing and analysis software and results were compared with manual methods. No significant differences in disomy frequencies were seen between the semi automated and manual methods. Samples treated with pepsin were observed to have reduced background autofluorescence and more uniform distribution of cells. These results demonstrate that semi-automated methods using spectral imaging on a confocal platform are a feasible approach for analyzing numerical chromosomal aberrations in sperm, and are comparable to manual methods. © 2017 International Society for Advancement of Cytometry.

Separase: Function Beyond Cohesion Cleavage and an Emerging Oncogene

Proper and timely segregation of genetic endowment is necessary for survival and perpetuation of every species. Mis-segregation of chromosomes and resulting aneuploidy leads to genetic instability, which can jeopardize the survival of an individual or population as a whole. Abnormality with segregation of genetic contents has been associated with several medical consequences including cancer, sterility, mental retardation, spontaneous abortion, miscarriages, and other birth related defects. Separase, by irreversible cleavage of cohesin complex subunit, paves the way for metaphase/anaphase transition during the cell cycle. Both over or reduced expression and altered level of separase have been associated with several medical consequences including cancer, as a result separase now emerges as an important oncogene and potential molecular target for medical intervenes. Recently, separase is also found to be essential in separation and duplication of centrioles. Here, I review the role of separase in mitosis, meiosis, non-canonical roles of separase, separase regulation, as a regulator of centriole disengagement, nonproteolytic roles, diverse substrates, structural insights, and association of separase with cancer. At the ends, I proposed a model which showed that separase is active throughout the cell cycle and there is a mere increase in separase activity during metaphase contrary to the common believes that separase is inactive throughout cell cycle except for metaphase. J. Cell. Biochem. 118: 1283-1299, 2017. © 2016 Wiley Periodicals, Inc.

Paternal or Maternal Uniparental Disomy of Chromosome 16 Resulting in Homozygosity of a Mutant Allele Causes Fanconi Anemia

Fanconi anemia (FA) is a rare inherited disorder caused by pathogenic variants in one of 19 FANC genes. FA patients display congenital abnormalities, and develop bone marrow failure, and cancer susceptibility. We identified homozygous mutations in four FA patients and, in each case, only one parent carried the obligate mutant allele. FANCA and FANCP/SLX4 genes, both located on chromosome 16, were the affected recessive FA genes in three and one family respectively. Genotyping with short tandem repeat markers and SNP arrays revealed uniparental disomy (UPD) of the entire mutation-carrying chromosome 16 in all four patients. One FANCA patient had paternal UPD, whereas FA in the other three patients resulted from maternal UPD. These are the first reported cases of UPD as a cause of FA. UPD indicates a reduced risk of having another child with FA in the family and has implications in prenatal diagnosis.

[Epidemiology of loss pregnancy]

OBJECTIVES

Study of epidemiology of pregnancy loss.

MATERIALS AND METHOD

A systematic review of the literature was performed using Pubmed and the Cochrane library databases and the guidelines from main international societies.

RESULTS

The occurrence of first trimester miscarriage is 12% of pregnancies and 25% of women. Miscarriage risk factors are ages of woman and man, body mass index greater than or equal to 25kg/m(2), excessive coffee drinking, smoking and alcohol consumption, exposure to magnetic fields and ionizing radiation, history of abortion, some fertility disorders and impaired ovarian reserve. Late miscarriage (LM) complicates less than 1% of pregnancies. Identified risk factors are maternal age, low level of education, living alone, history of previous miscarriage, of premature delivery and of previous termination of pregnancy, any uterine malformation, trachelectomy, existing bacterial vaginosis, amniocentesis, a shortened cervix and a dilated cervical os with prolapsed membranes. Fetal death in utero has a prevalence of 2% in the world and 5/1000 in France. Its main risk factors are detailed in the chapter.

Live birth after PGD with confirmation by a comprehensive approach (karyomapping) for simultaneous detection of monogenic and chromosomal disorders

Preimplantation genetic diagnosis (PGD) for monogenic disorders has the drawback of time and cost associated with tailoring a specific test for each couple, disorder, or both. The inability of any single assay to detect the monogenic disorder in question and simultaneously the chromosomal complement of the embryo also limits its application as separate tests may need to be carried out on the amplified material. The first clinical use of a novel approach ('karyomapping') was designed to circumvent this problem. In this example, karyomapping was used to confirm the results of an existing PGD case detecting both chromosomal abnormalities and a monogenic disorder (Smith-Lemli-Opitz [SLO] syndrome) simultaneously. The family underwent IVF, ICSI and PGD, and both polar body and cleavage stage biopsy were carried out. Following whole genome amplification, array comparative genomic hybridisation of the polar bodies and minisequencing and STR analysis of single blastomeres were used to diagnose maternal aneuploidies and SLO status, respectively. This was confirmed, by karyomapping. Unlike standard PGD, karyomapping required no a-priori test development. A singleton pregnancy and live birth, unaffected with SLO syndrome and with no chromosome abnormality, ensued. Karyomapping is potentially capable of detecting a wide spectrum of monogenic and chromosome disorders and, in this context, can be considered a comprehensive approach to PGD.

Association between response to ovarian stimulation and miscarriage following IVF: an analysis of 124 351 IVF pregnancies

STUDY QUESTION

Is there a relationship between ovarian reserve, quantified as ovarian response to stimulation, and miscarriage rate following IVF treatment?

SUMMARY ANSWER

There is a strong association between the number of oocytes retrieved and miscarriage rate following IVF treatment, with the miscarriage rate decreasing with an increasing number of oocytes and then levelling off: poor responders have a higher miscarriage rate across all age groups.

WHAT IS ALREADY KNOWN

Poor ovarian response is a manifestation of a decline in the quantity of the primordial follicle pool. Whether poor ovarian response is associated with a decline in oocyte quality contributing to miscarriage is however debated.

STUDY DESIGN, SIZE, DURATION

Anonymous data were obtained from the Human Fertilization and Embryology Authority (HFEA), the statutory regulator of assisted reproduction treatment (ART) in the UK. The HFEA has collected data on all ART performed in the UK since 1991. Data from 1991 to June 2008 involving 402 185 stimulated fresh IVF cycles and 124 351 pregnancy outcomes were analysed.

PARTICIPANTS/ MATERIALS, SETTING, METHODS

Data on all women undergoing a stimulated fresh IVF treatment cycle with at least one oocyte retrieved during the period from 1991 to June 2008 were analysed for their early pregnancy outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

There was a strong association between the number of oocytes retrieved and the clinical miscarriage rate. The miscarriage rate fell from 20 to 13% with an increasing number of oocytes before levelling off. Stepwise logistic regression identified three cut-off points (4, 10 and 15 oocytes) at or beyond which the probability of clinical miscarriage fell. There was no increase in miscarriage rate with very high oocyte numbers (>20 oocytes). The lowest risk of miscarriage (9.9%) was for women under 38 years of age, with primary infertility without a female cause and producing more than three oocytes.

LIMITATIONS, REASONS FOR CAUTION

Although the analysis was performed only on stimulated IVF cycles (excluding unstimulated cycles), the data had the limitation that there was no information on the total gonadotrophin consumption. The model was adjusted for age and type of infertility, but the dataset contained no information on other confounders such as body mass index (BMI) of the women to allow adjustment.

WIDER IMPLICATIONS FOR THE FINDINGS

Analysis of this extensive dataset suggests that poor responders have a higher risk of clinical miscarriage, indicating that poor ovarian response is associated with a parallel decline in both oocyte quantity and quality. The miscarriage rate is also higher with advanced age, secondary infertility and a female cause of infertility compared with a younger age, male factor infertility and unexplained cause.

Preimplantation genetic screening: does it help or hinder IVF treatment and what is the role of the embryo?

Despite an ongoing debate over its efficacy, preimplantation genetic screening (PGS) is increasingly being used to detect numerical chromosomal abnormalities in embryos to improve implantation rates after IVF. The main indications for the use of PGS in IVF treatments include advanced maternal age, repeated implantation failure, and recurrent pregnancy loss. The success of PGS is highly dependent on technical competence, embryo culture quality, and the presence of mosaicism in preimplantation embryos. Today, cleavage stage biopsy is the most commonly used method for screening preimplantation embryos for aneuploidy. However, blastocyst biopsy is rapidly becoming the more preferred method due to a decreased likelihood of mosaicism and an increase in the amount of DNA available for testing. Instead of using 9 to 12 chromosome FISH, a 24 chromosome detection by aCGH or SNP microarray will be used. Thus, it is advised that before attempting to perform PGS and expecting any benefit, extended embryo culture towards day 5/6 should be established and proven and the clinical staff should demonstrate competence with routine competency assessments. A properly designed randomized control trial is needed to test the potential benefits of these new developments.

Sperm chromatin dispersion test in the assessment of DNA fragmentation and aneuploidy in human spermatozoa

Sperm DNA damage is thought to be increased in men with male factor infertility. Previous studies suggest a correlation between sperm DNA fragmentation and aneuploidy. The sperm chromatin dispersion (SCD) test was modified to produce the Halosperm Kit. The SCD-fluorescent in-situ hybridization (FISH) test allows the simultaneous detection of DNA fragmentation and aneuploidy on the same sperm cell. The objectives of this study were to validate the SCD, SCD-FISH and Halosperm tests for the analysis of sperm DNA fragmentation and compare them to the sperm chromatin structure assay (SCSA). Semen samples from 20 males undergoing IVF/intracytoplasmic sperm injection were processed using FISH, SCD-FISH, SCD and Halosperm, and compared with SCSA results. There was a significant difference between FISH and SCD-FISH results in the detection of aneuploidy (P=0.000) and the level of sperm DNA fragmentation in the samples subjected to SCSA and SCD (P=0.001) or SCSA and SCD-FISH (P=0.001). There was no significant correlation between DNA fragmentation and aneuploidy. If sperm aneuploidy is to be determined, more reliable results will be obtained if FISH is performed rather than SCD-FISH. A lack of validation and unknown clinical significance question the value of DNA fragmentation assays. DNA damage in the male germ line may result in adverse clinical outcomes and the pathophysiology and clinical consequences of sperm DNA damage are being actively researched. Many DNA fragmentation assays such as the Halosperm Kit have been developed recently and are now available at a commercial level. Unfortunately, aimed at vulnerable couples with difficulty conceiving, many of these tests have not been clinically validated. Despite its plausible appeal and fervour of its supporters, the benefits of widespread DNA testing that only achieves the distressing of couples with the knowledge that effectual therapeutic strategies are absent are questionable. Commercially, however, it is no doubt lucrative. Analysis of gametes prior to the initiation of an IVF cycle may improve the quality of embryos transferred. The clinical and scientific community considers it a matter of urgency to translate the basic science behind how a cell prepares for fertilization into routine clinical practice. However, it is equally important, if not more, to allow the science behind such applications to draw level with its practice before its widespread implementation.

A mouse embryonic stem cell bank for inducible overexpression of human chromosome 21 genes

Background

Dosage imbalance is responsible for several genetic diseases, among which Down syndrome is caused by the trisomy of human chromosome 21.

Results

To elucidate the extent to which the dosage imbalance of specific human chromosome 21 genes perturb distinct molecular pathways, we developed the first mouse embryonic stem (ES) cell bank of human chromosome 21 genes. The human chromosome 21-mouse ES cell bank includes, in triplicate clones, 32 human chromosome 21 genes, which can be overexpressed in an inducible manner. Each clone was transcriptionally profiled in inducing versus non-inducing conditions. Analysis of the transcriptional response yielded results that were consistent with the perturbed gene's known function. Comparison between mouse ES cells containing the whole human chromosome 21 (trisomic mouse ES cells) and mouse ES cells overexpressing single human chromosome 21 genes allowed us to evaluate the contribution of single genes to the trisomic mouse ES cell transcriptome. In addition, for the clones overexpressing the Runx1 gene, we compared the transcriptome changes with the corresponding protein changes by mass spectroscopy analysis.

Conclusions

We determined that only a subset of genes produces a strong transcriptional response when overexpressed in mouse ES cells and that this effect can be predicted taking into account the basal gene expression level and the protein secondary structure. We showed that the human chromosome 21-mouse ES cell bank is an important resource, which may be instrumental towards a better understanding of Down syndrome and other human aneuploidy disorders.

Gamete cytogenetic study in couples with implantation failure: aneuploidy rate is increased in both couple members

PURPOSE

Implantation failure is known to be associated with an increased risk of aneuploidy in embryos, a situation leading to a pre-implantation genetic screening, not allowed in different countries like France. Our aim was to evaluate the gamete aneuploidy incidence in this context, using first polar body and spermatozoa aneuploidy screening.

METHODS

Three groups were considered: 11 couples with pregnancy obtained after IVF for female infertility (group 1); 20 couples with pregnancy obtained after IVF for male infertility (group 2); and 35 couples with implantation failure (group 3). In group 3, 28 couples treated by ICSI volunteered for first polar body analysis (PB1).

RESULTS

Spermatozoa aneuploidy rate was increased in groups 2 (1.6%) and 3 (2.1%) in comparison to group 1 (0.6%). PB1 aneuploidy rate was 35.4% in group 3. Finally, eight couples (32%) had no particular chromosomal risk in gametes, 15/25 (60%) presented an increased spermatic (>2%) or oocyte (>1/3) aneuploidy rate, and 2/25 (8%) had both.

CONCLUSION

Those results confirm that implantation failure has a heterogeneous origin, that gamete chromosome abnormality rate is one of the major contributing factors, and that 1st Polar body and spermatozoa aneuploidy screening or pre-implantation genetics screening may be indicated for these couples.

A high oocyte yield for intracytoplasmic sperm injection treatment is associated with an increased chromosome error rate

OBJECTIVE

To compare the chromosome error rate among oocytes from stimulated ovaries after retrieval of 1-5 oocytes, 6-10 oocytes, and >10 oocytes.

DESIGN

Retrospective cohort study.

SETTING

A university-based human genetic institute in collaboration with a private fertility center.

PATIENT(S)

Nine hundred thirty-three women undergoing intracytoplasmic sperm injection (ICSI) with a poor prognosis.

INTERVENTION(S)

Oocyte collection with ovarian stimulation. Polar body testing of ICSI oocytes for common chromosome errors.

MAIN OUTCOME MEASURE(S)

Chromosome error rate in oocytes, as determined by five-color fluorescence in situ hybridization.

RESULT(S)

In women less than 35 years and women between 35 and 40 years undergoing the first ICSI cycle, oocytes from the high-yield group had an increased likelihood for detectable chromosome errors (50.9% and 54.6%, respectively), compared to the intermediate-yield group (34.9% and 43.8%) and the low-yield group (23.3% and 41.2%). The overall high rate (>or=50%) of chromosomally abnormal oocytes in women more than 40 years appeared to be mainly due to the maternal age effect and increased only slightly with oocyte yield.

CONCLUSION(S)

Oocyte yield may be considered as an indicator of ovarian response to hormone stimulation. In women up to 40 years a high yield of oocytes after superovulation is associated with an increased chromosome error rate.

Nuclear organisation in totipotent human nuclei and its relationship to chromosomal abnormality

Studies of nuclear organisation, most commonly determining the nuclear location of chromosome territories and individual loci, have furthered our understanding of nuclear function, differentiation and disease. In this study, by examining eight loci on different chromosomes, we tested hypotheses that: (1) totipotent human blastomeres adopt a nuclear organisation akin to that of committed cells; (2) nuclear organisation is different in chromosomally abnormal blastomeres; and (3) human blastomeres adopt a `chromocentre' pattern. Analysis of in vitro fertilisation (IVF) conceptuses permits valuable insight into the cell biology of totipotent human nuclei. Here, extrapolations from images of preimplantation genetic screening (PGS) cases were used to make comparisons between totipotent blastomeres and several committed cells, showing some differences and similarities. Comparisons between chromosomally abnormal nuclei and those with no detected abnormality (NDA) suggest that the former display a significant non-random pattern for all autosomal loci, but there is a less distinct, possibly random, pattern in `NDA' nuclei. No evidence was found that the presence of an extra chromosome is accompanied by an altered nuclear location for that chromosome. Centromeric loci on chromosomes 15 and 16 normally seen at the nuclear periphery were mostly centrally located in aneuploid cells, providing some evidence of a `chromocentre'; however, the chromosome-18 centromere was more peripheral, similar to committed cells. Our results provide clues to the nature of totipotency in human cells and might have future applications for preimplantation diagnosis and nuclear transfer.

Oocyte aneuploidy mechanisms are different in two situations of increased chromosomal risk: older patients and patients with recurrent implantation failure after in vitro fertilization

OBJECTIVE

To clarify the mechanisms underlying oocyte abnormalities in meiosis: meiotic nondisjunction of a whole chromosome or premature separation of sister chromatids in two situations of increased chromosomal risk.

DESIGN

Preconception diagnosis by first polar-body analysis in two situations of increased chromosomal risk.

SETTING

Departments of reproductive biology, cytogenetics, gynecology, and obstetrics.

PATIENT(S)

First polar body analysis was proposed to 76 patients (91 cycles) for advanced age (AMA; n = 30, 36 cycles), recurrent implantation failure (RIF; >10 embryos transferred without implantation; n = 32, 36 cycles), or both (AMA + RIF; n = 14, 19 cycles), before their intracytoplasmic sperm injection procedure.

INTERVENTION(S)

First polar-body analysis using fluorescence in situ hybridization.

MAIN OUTCOME MEASURE(S)

Mechanisms and frequency of aneuploidy.

RESULT(S)

Three hundred eighty-four oocytes were analyzed by fluorescence in situ hybridization, 130 from women >38 years of age, 171 from women with RIF, and 83 from women with both indications. The oocyte abnormality rate was similar in the three groups, respectively, 38.5%, 40.4%, and 45.8%. The aneuploidy mechanisms were different for women >38 years of age who had no previous implantation failure (AMA) compared with women of whatever age who had implantation failure (P<.05 vs. RIF; P<.001 vs. AMA+RIF), with, respectively, for the AMA, RIF, and AMA+RIF groups, 72.2%, 56.6%, and 49.2% premature separation of sister chromatids and 27.8%, 43.4%, and 50.8% meiotic nondisjunction. In the two implantation-failure groups, we distinguished a subgroup (22% in the RIF group and 33% in AMA+RIF group) of patients with >2/3 abnormal oocytes, suggesting a meiosis alteration.

CONCLUSION(S)

The mechanisms accounting for oocyte aneuploidy differed in the two clinical situations of advanced maternal age and RIF. Advanced maternal-age aneuploidy was linked to a loss of sister chromatid cohesion that led to one single chromatid abnormality, whereas implantation failure is a much more heterogeneous situation.

Analysis of sex chromosome abnormalities using X and Y chromosome DNA tiling path arrays

BACKGROUND

Array comparative genomic hybridisation is a powerful tool for the detection of copy number changes in the genome.

METHODS

A human X and Y chromosome tiling path array was developed for the analysis of sex chromosome aberrations.

RESULTS

Normal X and Y chromosome profiles were established by analysis with DNA from normal fertile males and females. Detection of infertile males with known Y deletions confirmed the competence of the array to detect AZFa, AZFb and AZFc deletions and to distinguish between different AZFc lesions. Examples of terminal and interstitial deletions of Xp (previously characterised through cytogenetic and microsatellite analysis) have been assessed using the arrays, thus both confirming and refining the established deletion breakpoints. Breakpoints in iso-Yq, iso-Yp and X-Y translocation chromosomes and X-Y interchanges in XX males are also amenable to analysis.

DISCUSSION

The resolution of the tiling path clone set used allows breakpoints to be placed within 100-200 kb, permitting more precise genotype/phenotype correlations. These data indicate that the combined X and Y tiling path arrays provide an effective tool for the investigation and diagnosis of sex chromosome copy number aberrations and rearrangements.

Cerebral palsy due to chromosomal anomalies and continuous gene syndromes

When cerebral palsy is defined as a disorder of movement and posture that is due to nonprogressive disturbances that occur in the developing fetal and infant brain, a significant proportion-up to 10%--is the consequence of chromosomal anomalies and continuous gene syndromes. Abnormalities of chromosomes are constitutional or acquired. Acquired chromosomal abnormalities develop postnatally, affect only one clone of cells, and are implicated in the evolution of neoplasia. Constitutional abnormalities develop during gametogenesis or early embryogenesis and affect a significant portion of the subject's cells.

The effect of epigenetic sperm abnormalities on early embryogenesis

Sperm are a highly specialized cell type derived to deliver the paternal haploid genome to the oocyte. The epigenetic, or gene regulatory, properties and mechanisms of the sperm assist in preparation of the paternal genome to contribute to embryogenesis and the genome of the zygote. Many recent studies have addressed the issue of altered epigenetic processes in the sperm. This review evaluates the current understanding of DNA damage, chromosome aneuploidy, reduced telomere length, malformations of the centrosome, genomic imprinting errors, altered mRNA profiles, and abnormal nuclear packaging in the sperm prior to fertilization and the observed effects on embryogenesis. Attention has also been given to understanding the underlying etiology of sperm with altered epigenetic mechanisms in humans.

Chromosomal variation in mammalian neuronal cells: known facts and attractive hypotheses

Chromosomal mosaicism is still a genetic enigma. Although the mechanisms and consequences of this phenomenon have been studied for over 50 years, there are a number of gaps in our knowledge concerning causes, genetic mechanisms, and phenotypic manifestations of chromosomal mosaicism. Neuronal cell-specific chromosomal mosaicism is not an exception. Originally, neuronal cells of the mammalian brain were assumed to possess identical genomes. However, recent studies have shown chromosomal variations, manifested as chromosome abnormalities in cells of the developing and adult mammalian nervous system. Here, we review data obtained on the variation in chromosome complement in mammalian neuronal cells and hypothesize about the possible relevance of large-scale genomic (i.e., chromosomal) variations to brain development and functions as well as neurodevelopmental and neurodegenerative disorders. We propose to cover the term "molecular neurocytogenetics to cover all studies the aim of which is to reveal chromosome variations and organization in the mammalian brain.

Recruitment of sperm donors: the Newcastle-upon-Tyne experience 1994–2003

BACKGROUND

The demand for sperm donors has continued despite the introduction of ICSI. This study was undertaken in the light of impending changes in donor anonymity laws to evaluate the recruitment process of sperm donors.

METHODS

Retrospective analysis of 1101 potential sperm donors in a tertiary referral centre between January 1994 and August 2003. The main outcome measures were to determine the demographic details, recruitment rate and reasons for rejection of donors.

RESULTS

The majority of the applicants were aged <36 years (88.07%), students (54.88%), without a partner (53.47%), unmarried (85.38%) and without proven fecundity (78.67%). Only 3.63% of the applicants were released as donors, 30.79% defaulted, whilst 64.48% were rejected. The most common reason for rejection was suboptimal semen quality (85.07%). Over the years, the numbers of the applicants and released donors have declined significantly. The overall clinical pregnancy rate from donor sperm during this period was 23.52%.

CONCLUSIONS

In this successful anonymous sperm donor programme only a small proportion of the applicants are released as donors. The significant decline in released sperm donors coupled with the potential effects of loss of donor anonymity means that new strategies for sperm donor recruitment are urgently required.

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.

Trichlorfon predisposes to aneuploidy and interferes with spindle formation in in vitro maturing mouse oocytes

The pesticide trichlorfon (TCF) has been implicated in human trisomy 21, and in errors in chromosome segregation at male meiosis II in the mouse. We previously provided evidence that TCF interferes with spindle integrity and cell-cycle control during murine oogenesis. To assess the aneugenic activity of TCF in oogenesis, we presently analysed maturation, spindle assembly, and chromosome constitution in mouse oocytes maturing in vitro in the presence of 50 or 100 microg/ml TCF for 16 h or in pulse-chase experiments. TCF stimulated maturation to meiosis II at 50 microg/ml, but arrested meiosis in some oocytes at 100 microg/ml. TCF at 100 microg/ml was aneugenic causing non-disjunction of homologous chromosomes at meiosis I, a significant increase of the hyperploidy rate at metaphase II, and a significant rise in the numbers of oocytes that contained a 'diploid' set of metaphase II chromosomes (dyads). TCF elevated the rate of precocious chromatid segregation (predivision) at 50 and 100 microg/ml. Pulse-chase experiments with 100 microg/ml TCF present during the first 7 h or the last 9 h of maturation in vitro did not affect meiotic progression and induced intermediate levels of hyperploidy at metaphase II. Exposure to > or =50 microg/ml TCF throughout maturation in vitro induced severe spindle aberrations at metaphase II, and over one-third of the oocytes failed to align all chromosomes at the spindle equator (congression failure). These observations suggest that exposure to high concentrations of TCF induces non-disjunction at meiosis I of oogenesis, while lower doses may preferentially cause errors in chromosome segregation at meiosis II due to disturbances in spindle function, and chromosome congression as well as precocious separation of chromatids prior to anaphase II. The data support evidence from other studies that TCF has to be regarded as a germ cell aneugen.

Features of chromosomal abnormalities in spontaneous abortion cell culture failures detected by interphase FISH analysis

Cytogenetic analysis of reproductive wastage is an important stage in understanding the genetic background of early embryogenesis. The results of conventional cytogenetic studies of spontaneous abortions depend on tissue culturing and are associated with a significant cell culture failure rate. We performed interphase dual-colour FISH analysis to detect chromosomal abnormalities in noncultured cells from two different tissues-cytotrophoblast and extraembryonic mesoderm-of 60 first-trimester spontaneous abortions from which cells had failed to grow in culture. An original algorithm was proposed to optimize the interphase karyotype screening with a panel of centromere-specific DNA probes for all human chromosomes. The overall rate of numerical chromosomal abnormalities in these cells was 53%. Both typical and rare forms of karyotype imbalance were found. The observation of six cases (19%) of monosomy 7, 15, 21 and 22 in mosaic form, with a predominant normal cell line, was the most unexpected finding. Cell lines with monosomies 21 and 22 were found both in cytotrophoblast and mesoderm, while cells with monosomy 7 and 15 were confined to the cytotrophoblast. The tissue-specific compartmentalization of cell lines with autosomal monosomies provides evidence that the aneuploidy of different human chromosomes may arise during different stages of intrauterine development. The effect of aneuploidy on selection may differ, however, depending on the specific chromosome. The abortions also revealed a high frequency of intratissue chromosomal mosaicism (94%), in comparison with that detected by conventional cytogenetic analysis (29%; P<0.001). Confined placental mosaicism was found in 25% of the embryos. The results of molecular cytogenetic analysis of these cell culture failures illustrate that the diversity and phenotypic effects of chromosomal abnormalities during the early stages of human development are underestimated.

Numerical chromosomal abnormalities in rat epididymal spermatozoa following chronic cyclophosphamide exposure

Chronic, low-dose treatment of male rats with cyclophosphamide, a chemotherapeutic agent, is known to affect progeny outcome adversely in a dose-dependent and time-specific manner, resulting in increased pre- and postimplantation loss as well as malformations. Concern exists regarding the genetic quality of mature gametes exposed to cyclophosphamide during mitosis and meiosis. The goal of the present study was to determine the effect of chronic cyclophosphamide treatment during spermatogenesis on the frequency of numerical chromosomal anomalies in epididymal spermatozoa. Male rats were treated with either saline or cyclophosphamide (6 mg kg-1 day-1) for 6 or 9 wk, and cauda epididymal spermatozoa were collected. The rat sperm Y-4 fluorescence in situ hybridization assay was used to assess the induction of spermatozoal disomy, nullisomy, and diploidy involving chromosomes Y and 4. The overall frequency of numerically abnormal spermatozoa was elevated approximately 2-fold (P < 0.001) after 9 wk of cyclophosphamide treatment. Exposure for 9 wk, but not for 6 wk, significantly increased the frequency of spermatozoa with chromosome 4 disomy (P < 0.02) and nullisomy (P < 0.05), but disomy Y and diploidy were not significantly increased with treatment compared to corresponding controls. Independent of treatment, only 27% of aneuploid spermatozoa presented with morphological abnormalities, but all diploid spermatozoa were approximately twice the size of normal cells. Thus, cyclophosphamide disrupts meiotic events before pachynema during spermatogenesis, emphasizing the potential for adverse progeny outcomes following genotoxic damage.

A probability model for the meiosis I non-disjunction fraction in numerical chromosomal anomalies

Numerical chromosome abnormalities (aneuploidies) are among the most common known causes of mental retardation and the leading cause of pregnancy loss in humans. They primarily arise by the process of meiotic non-disjunction. We still know very little about the contribution of genetic and environmental causes for non-disjunction in humans. In order to increase our understanding of the epidemiology of human trisomies, it is necessary to establish the proportion of cases occurring in the first or second division of meiosis. Trisomic patients will display, in study of microsatellite typed by the polymerase chain reaction (PCR), three fragment peaks of equal intensity, two fragments at an average 2:1 dosage or one individual fragment. In this work we describe a statistical approach for estimation of the fraction of meiosis I non-disjunctions (F) in the absence of the parental information. First we determine a probability model for the number of peaks in a polymorphic microsatellite locus, which is a function of F. Based on this model, we obtain a maximum likelihood estimator for F, using the observed proportion of one, two and three allele patterns in trisomic individuals. Relying on the properties of maximum likelihood theory, we also calculate the asymptotic variance and confidence intervals for F. Owing to the fact that the samples of trisomic patients are limited in number, the use of asymptotic theory may be compromised. Thus, we employ the bootstrap technique to build confidence intervals for F and compare the results with those obtained from the normal theory. This estimator that dispenses the need to study parents opens the possibility of using archival material for comparative epidemiological studies of Down's syndrome and other aneuploidies. In this paper we propose a probability model to estimate the fraction of meiosis I non-disjunction, F, by only using the proportion of allele patterns of trisomy individuals, while traditional methods require typing pericentromeric markers from those affected and their parents.

Failed fertilization: is it predictable?

PURPOSE OF REVIEW

The purpose of this review is to critically examine the ability of screening tests to predict fertilization failure.

RECENT FINDINGS

Failed fertilization occurs in 5-10% of in-vitro fertilization cycles and 2-3% of intracytoplasmic sperm injection cycles. Failed fertilization may result from impaired spermatozoa, oocyte deficiencies or defects in the in-vitro sperm/oocyte medium. In the in-vitro fertilization setting most cases are caused by male factor deficiencies, whereas failure of oocyte activation is the most common cause of failed fertilization after intracytoplasmic sperm injection. Although the standard semen analysis has limited ability to predict fertilization failure, strict sperm morphology criteria, sperm-zona binding ratios and zona pellucida induced acrosome reaction tests provide increased capacity to avoid this outcome. The quality of the semen sample on the day of oocyte retrieval and fertilization performance in previous in-vitro fertilization cycles may also guide the appropriate use of intracytoplasmic sperm injection. However, the routine use of the latter technique in cases of non-male factor infertility is contraindicated.

SUMMARY

The ever improving techniques highlighted in this analysis offer improved ability to predict failed fertilization.

Enhancing the in vitro and in vivo detection of aneuploidy by fluorescence in situ hybridization with the use of bromodeoxyuridine as a proliferation marker

Aneuploidy is associated with spontaneous abortions, birth defects, and many types of human cancers. Currently there are few assays developed for the efficient detection of aneuploidy in vivo. However, with the recent availability of chromosome-specific DNA probes for the rat, fluorescence in situ hybridization (FISH) techniques could be used for the rapid and sensitive detection of aneuploidy in different tissue and cell types. In order to develop a system that can detect alterations in chromosome number in rat cells in vitro, we treated cultured rat lymphocytes with three aneugens-noscapine hydrochloride (0-150 microM) and vincristine and vinblastine sulfate (0-0.06 microM). 5-Bromo-2-deoxyuridine (BrdU; 1 microM) was added to the culture medium to allow proliferating and non-proliferating cells to be distinguished. To test this assay under in vivo conditions, 21-day-old male Sprague-Dawley rats were subcutaneously implanted with osmotic pumps that delivered BrdU (approximately 12 mg/kg per day) continuously. These rats were administered vinblastine sulfate (0, 0.5 and 1mg/kg) by intraperitoneal injection. The rat lymphocytes and hepatocytes incorporating BrdU were detected by immuno-fluorescent labeling, and FISH with a rat chromosome 4 probe was performed on the labeled and unlabeled cells. Highly significant increases in hyperdiploidy were seen in the replicating rat lymphocytes treated with noscapine, vincristine or vinblastine in vitro and in the rat hepatocytes treated with vinblastine in vivo. In contrast, no significant increase in hyperdiploidy was observed in the non-replicating cells. These results demonstrate that this BrdU-enhanced FISH assay with chromosome-specific rat probes can be used to efficiently detect numerical chromosomal aberrations in vitro and in vivo in slowly or moderately replicating rat tissues. The combination of BrdU-labeling and FISH allows the scoring of hyperdiploidy to be focused on the actively replicating cells, thereby increasing the sensitivity of the FISH technique.

Endoreduplication of the hyperhaploid maternal complement and abnormal pronuclear formation in a human zygote obtained after intracytoplasmic sperm injection

We report the cytogenetic analysis of a tripronuclear zygote with two polar bodies observed after intracytoplasmic sperm injection. Rare previous investigations of this kind of zygote suggested a diploid or a hypotriploid chromosome constitution. In contrast, the present case turned out to be hypertriploid. Besides the haploid (23,Y) sperm chromosome set, there was a hyperdiploid endoreduplicated (end48,XX,+18,+18) maternal contribution. This zygote not only revealed a peculiar combination of different anomalies (hyperhaploidy of the female gamete, endoreduplication and abnormal pronuclear formation) but also indicates that endoreduplication may sporadically contribute to the generation of triploidy.

Disseminating the genome: joining, resolving, and separating sister chromatids during mitosis and meiosis

The separation of sister chromatids at the metaphase to anaphase transition is one of the most dramatic of all cellular events and is a crucial aspect of all sexual and asexual reproduction. The molecular basis for this process has until recently remained obscure. New research has identified proteins that hold sisters together while they are aligned on the metaphase plate. It has also shed insight into the mechanisms that dissolve sister chromatid cohesion during both mitosis and meiosis. These findings promise to provide insights into defects in chromosome segregation that occur in cancer cells and into the pathological pathways by which aneuploidy arises during meiosis.

Frequency of XY sperm increases with age in fathers of boys with Klinefelter syndrome

With increasing availability of drugs for impotence and advanced reproductive technologies for the treatment of subfertility, more men are fathering children at advanced ages. We conducted a study of the chromosomal content of sperm of healthy men aged 24-57 years to (a) determine whether father's age was associated with increasing frequencies of aneuploid sperm including XY, disomy X, disomy Y, disomy 21, and sperm diploidy, and (b) examine the association between the frequencies of disomy 21 and sex-chromosomal aneuploidies. The study group consisted of 38 fathers of boys with Klinefelter syndrome (47, XXY) recruited nationwide, and sperm aneuploidy was assessed using multicolor X-Y-21 sperm FISH ( approximately 10,000 sperm per donor). Paternal age was significantly correlated with the sex ratio of sperm (Y/X; P=.006) and with the frequency of XY sperm (P=.02), with a clear trend with age by decades (P<.006). Compared with fathers in their 20s (who had an average frequency of 7.5 XY sperm per 10,000), the frequencies of XY sperm were 10% higher among fathers in their 30s, 31% higher among those in their 40s, and 160% higher among those in their 50s (95% CI 69%-300%). However, there was no evidence for age effects on frequencies of sperm carrying nullisomy sex; disomies X, Y, or 21; or meiosis I or II diploidies. The frequencies of disomy 21 sperm were significantly associated with sex-chromosomal aneuploidy (P=.04)-in particular, with disomy X (P=.004), but disomy 21 sperm did not preferentially carry either sex chromosome. These findings suggest that older fathers produce higher frequencies of XY sperm, which may place them at higher risk of fathering boys with Klinefelter syndrome, and that age effects on sperm aneuploidy are chromosome specific.

The ZW10 and Rough Deal checkpoint proteins function together in a large, evolutionarily conserved complex targeted to the kinetochore

The zeste-white 10 (zw10) and rough deal (rod) genes of Drosophila both encode kinetochore components, and mutations in either gene greatly increase the missegregation of sister chromatids during mitosis. Here, we present genetic, cytological and biochemical evidence for a close, evolutionarily conserved relationship between the ROD and ZW10 proteins. We show that the phenotypes caused by disruption of either gene’s function are similar in Drosophila and in C. elegans. No additive effects are observed in zw10; rod double null mutants. In flies, the two proteins always colocalize and, moreover, require each other for their recruitment to the mitotic apparatus. The human ROD and ZW10 homologs also colocalize on HeLa cell kinetochores or kinetochore microtubules throughout most but not all of mitosis. Finally, we show that in both Drosophila and human cells, ROD and ZW10 are in fact physically associated, and in Drosophila these proteins are together constituents of a large (700-900 kDa), soluble macromolecular complex.

Meiotic nondisjunction of chromosomes 1, 17, 18, X, and Y in men more than 80 years of Age

In order to evaluate a possible paternal age effect, testicular sperm cells from three men aged 81, 82, and 83 yr were analyzed by two-color- and three-color-fluorescence in situ hybridization for disomy rates of chromosomes 1, 17, 18, X, and Y as well as for diploidy frequencies. A minimum of 1500 sperm cells per donor and probe was evaluated due to the low number of spermatozoa in the preparations. Diploidy and disomy frequencies were in the same range as found in men aged <30 yr, a slight increase only being noticed for XY nuclei.

Cleavage of cohesin by the CD clan protease separin triggers anaphase in yeast

In eukaryotic cells, replicated DNA strands remain physically connected until their segregation to opposite poles of the cell during anaphase. This "sister chromatid cohesion" is essential for the alignment of chromosomes on the mitotic spindle during metaphase. Cohesion depends on the multisubunit cohesin complex, which possibly forms the physical bridges connecting sisters. Proteolytic cleavage of cohesin's Sccl subunit at the metaphase to anaphase transition is essential for sister chromatid separation and depends on a conserved protein called separin. We show here that separin is a cysteine protease related to caspases that alone can cleave Sccl in vitro. Cleavage of Sccl in metaphase arrested cells is sufficient to trigger the separation of sister chromatids and their segregation to opposite cell poles.

Increased nondisjunction of chromosome 21 with age in human peripheral lymphocytes

Fluorescence in situ hybridization (FISH) on binucleated cells with chromosome-specific DNA probes provides a convenient way to visualize reciprocal segregation patterns in daughter nuclei, and overcomes most problems related to the artefactual loss or gain of chromosomes that flaw chromosome preparations. In this study, FISH was employed to evaluate age- and sex-effects on spontaneous malsegregation, nondisjunction and loss of chromosome 21 in human lymphocytes after the first division in culture. A total of 68 healthy nonsmokers and nondrinkers of alcohol (37 males and 31 females) were grouped by age as Group I (0-10 years), Group II (20-30 years), Group III (40-50 years) and Group IV (60-70 years), with at least seven subjects per group and sex. FISH with a pericentric chromosome 21 specific DNA probe was carried out on binucleated lymphocytes, cytokinesis-blocked by cytochalasin B (6 microg/ml for 26 h) at 44 h after initiation of cultures. Linear regression analyses demonstrated a significant age-related increase in the frequency of micronuclei without chromosome 21 (MN-21)(r=0.73, p<0.001 in females; r=0.69, p<0.001 in males) in all binucleated cells, with a steeper slope in females (0.1758) than in males (0. 1241). Analysis using the 2x2 chi-square (chi(2)) test on the frequencies of MN-21 showed significant age-related differences in both males and females, except males in Group III and Group IV (p>0. 05). A significant sex-related difference was found only in subjects over 60 years (p<0.05), with females having more MN-21 (12.57 per thousand vs. 8.43 per thousand) than males. Loss of chromosome 21, occurring at mean levels of 0.38 per thousand in all binucleated cells and 0.24 per thousand in binucleated cells containing four FISH signals, was shown not to be age- or sex-related. A positive age-related increase in nondisjunction of chromosome 21 was shown in males (r=0.50, p<0.01), females (r=0.61, p<0.001) and all subjects (r=0.55, p<0.001) by linear regression analysis. An age effect was found only between children and adults (p<0.01 for females, p<0.05

First confirmed case with paternal uniparental disomy of chromosome 16

The existence of paternal uniparental disomy of chromosome 16 [upd(16)pat] has previously been suspected but has not been proven. We report prenatal detection and follow-up of isodisomic upd(16)pat in a child with minimal defects but otherwise normal development. Our results indicate that isodisomic upd(16)pat is associated with a normal outcome if no recessive mutation is reduced to homozygosity.