Detection of chromosome aberrations in 17 054 individuals with fertility problems and their subsequent assisted reproductive technology treatments in Central China

STUDY QUESTION

How do the types and frequency of chromosome aberrations in couples in central China affect fertility and ART treatment?

SUMMARY ANSWER

Men with chromosome aberrations or polymorphisms have an increased risk of semen quality impairment and infertility, and couples affected by reciprocal translocations had a lower pregnancy rate compared with other chromosome aberrations.

WHAT IS KNOWN ALREADY

Karyotyping is crucial for patients affected by infertility as chromosome aberrations play an important role in the etiology of male infertility. However, the influence of chromosome aberrations and polymorphisms on sperm motility and morphology remains controversial. Data on ART treatment outcomes in infertile couples affected by chromosome aberrations are insufficient.

STUDY DESIGN, SIZE, DURATION

We conducted a retrospective study involving 17 054 patients affected by infertility who underwent karyotyping in our center between January 2020 and May 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Karyotyping was performed on 17 054 patients with reproductive failure. All patients were from the central regions of China. The following data were collected from a medical records system using patient identification numbers: couples' ages, history of pregnancy and childbirth, type of infertility, years of infertility, cause of infertility, chromosome karyotypes, semen analysis results, assisted reproductive techniques performed, and treatment outcomes of ART.

MAIN RESULTS AND THE ROLE OF CHANCE

The incidence of chromosome aberrations was 2.04%; 2.49% in men and 1.57% in women. By analyzing the relationships between chromosome aberrations/polymorphisms and abnormal semen parameters, we found that there were significantly higher rates of asthenozoospermia, oligospermia, and teratozoospermia among men with Robertsonian translocations and sex chromosomal structural aberrations compared with those with normal karyotypes. Higher rates of asthenozoospermia and teratozoospermia were also observed among men with autosomal reciprocal translocations. The incidence of chromosome aberrations in azoospermic men (13.75%), and in men with cryptozoospermia or severe oligospermia (6.97%) was significantly higher than that in men with mild oligospermia or normospermia (0.88-2.12%). In addition, we found that the progressive movement of sperm is impaired in men with Chromosome 21 polymorphisms compared with men with normal karyotypes (39.46% ± 20.51% vs 48.61% ± 18.76%, P = 0.026). The percentage of morphologically normal forms was lower in the chromosomal polymorphism group than in the normal karyotype group (5.01% ± 2.41% vs 5.59% ± 2.14%, P = 0.001), especially in men with polymorphisms on Chromosome 9 (enlarged Chromosome 9 heterochromatin [9qh+]: 4.48% ± 2.22% vs 5.59% ± 2.14%, P = 0.006; pericentric inversion of Chromosome 9 [inv(9)]: 5.09% ± 3.11% vs 5.59% ± 2.14%, P = 0.008). ART treatment was successful in 36.00% of couples affected by chromosome aberrations. However, couples affected by reciprocal translocations achieved a lower pregnancy rate (24.07%), which may be due to the lower euploidy rates (27.31%) when compared with that in other chromosome aberrations.

LIMITATIONS, REASONS FOR CAUTION

First, although the initial cohort was large, chromosome aberrations were identified in a small number of patients. Second, the observational nature of the study design is limiting. Third, the couples affected by infertility in this study were all outpatients that did not undergo identical comprehensive examinations except for karyotyping, leading to the incomplete collection of medical records. Also, the population included in this study mainly focused on couples affected by infertility, which may not be included in the European Association of Urology (EAU) recommendation on male infertility.

WIDER IMPLICATIONS OF THE FINDINGS

Men with chromosome aberrations or polymorphisms have an increased risk of semen quality impairment and infertility. Constitutional chromosome analysis is recommended for men affected by infertility and severe oligospermia or azoospermia to facilitate early and appropriate guidance for the most suitable treatment. Carriers of chromosome aberrations can achieve acceptable pregnancy outcomes through IVF. However, couples affected by reciprocal translocations have lower pregnancy rates, and more treatment cycles are needed before a successful pregnancy. A possible explanation may be the fewer euploid embryos obtained.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Grant 2021YFC2700603 from the National Key Research & Development Program of China. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Effect of chromosomal polymorphisms on the outcome of in vitro fertilization and embryo transfer

PURPOSE

The incidence of chromosomal polymorphisms (CP) is increased in infertile couples, but its impact on reproduction is uncertain, especially undergoing assisted reproductive technology treatment. The purpose of the present study was to investigate the effect of CP on the outcomes of in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) treatment METHODS: A total of 1331 infertile couples undergoing IVF/ICSI treatment were involved in this retrospective case-control study. The participants were divided into 4 groups according to CP variations: (i) normal chromosomes (NC) group; (ii) CP group; (iii) both chromosomal polymorphisms (BCP) group; and (iv) double chromosomal polymorphisms (DCP) group. The CP group was further divided into five subgroups: qh+, D/G, inv(9), Yqh+ and Yqh-. The outcomes of IVF/ICSI-ET treatment were compared among the groups.

RESULTS

There were no differences observed between the eight groups in terms of number of oocytes retrieved, MII rate, fertilization rate, cleaved embryo rate, and quality embryo rate for both females and males (p > 0.05). In both male and female, some of the CP subgroups experienced more oocyte retrieval operations and more embryo transfer operations to achieve pregnancy than the NC groups (p < 0.05). The rates of live births were significantly lower in some of the CP subgroups compared to the NC group (p < 0.05).

CONCLUSION

In conclusion, the pregnancy outcomes of ET were affected by CP. It was speculated that this may be associated with the effect of chromosome polymorphism on embryo quality, although this could not be observed or determined by morphological evaluation.

Chromosomal polymorphisms in assisted reproduction: a systematic review and meta-analysis

This systematic review and meta-analysis investigated the effects of chromosomal polymorphisms in reproductive outcomes following IVF or ICSI. Literature in CENTRAL, CINAHL, EMBASE and MEDLINE were searched from 1974 to March 2020 with no language restrictions. Ten published cohort studies were chosen for analysis. Studies included females, males and couples undergoing assisted reproductive treatments with the presence or absence of chromosomal polymorphisms. Reproductive outcomes were reported and their quality assessed using the Newcastle-Ottawa Quality Assessment Scale. Meta-analysis of five cohort studies (9,659 participants) indicated that female carriers with chromosomal polymorphisms had a higher miscarriage rate compared to non-carriers (risk ratio (RR) 1.54 (95% CI 1.19-1.98), whereas no significant association was found for males (RR 0.96, 95% CI 0.64-1.43) and couples (RR 1.93, 95% CI 0.32-11.83) indicating that this effect appeared to be gender-dependent. There was no association between chromosomal polymorphisms and a higher rate of biochemical, clinical, ongoing pregnancy, and preterm and live birth.

Wing trait-inversion associations in Drosophila subobscura can be generalized within continents, but may change through time

Clinal variation is one of the most emblematic examples of the action of natural selection at a wide geographical range. In Drosophila subobscura, parallel clines in body size and inversions, but not in wing shape, were found in Europe and South and North America. Previous work has shown that a bottleneck effect might be largely responsible for differences in wing trait-inversion association between one European and one South American population. One question still unaddressed is whether the associations found before are present across other populations of the European and South American clines. Another open question is whether evolutionary dynamics in a new environment can lead to relevant changes in wing traits-inversion association. To analyse geographical variation in these associations, we characterized three recently laboratory founded D. subobscura populations from both the European and South American latitudinal clines. To address temporal variation, we also characterized the association at a later generation in the European populations. We found that wing size and shape associations can be generalized across populations of the same continent, but may change through time for wing size. The observed temporal changes are probably due to changes in the genetic content of inversions, derived from adaptation to the new, laboratory environment. Finally, we show that it is not possible to predict clinal variation from intrapopulation associations. All in all this suggests that, at least in the present, wing traits-inversion associations are not responsible for the maintenance of the latitudinal clines in wing shape and size.

B chromosomes of rye are highly conserved and accompanied the development of early agriculture

BACKGROUND AND AIMS

Supernumerary B chromosomes (Bs) represent a specific type of selfish genetic element. As Bs are dispensable for normal growth, it is expected to observe B polymorphisms among populations. To address whether Bs maintained in geographically distinct populations of cultivated and weedy rye are polymorphic, the distribution patterns and the transcriptional activity of different B-located repeats were analysed.

METHODS

Bs of cultivated and weedy rye from seven origins were analysed by fluorescence in situ hybridization (FISH) with probes specific for the pericentromeric and interstitial regions as well as the B-specific non-disjunction control region. The DNA replication, chromatin composition and transcription behaviour of the non-disjunction regions were determined. To address whether the B-marker repeats E3900 and D1100 have diverged genotypes of different origin at the sequence level, the genomic sequences of both repeats were compared between cultivated rye and weedy rye from five different origins.

KEY RESULTS

B chromosomes in cultivated and weedy rye have maintained a similar molecular structure at the level of subspecies. The high degree of conservation of the non-disjunction control region regarding its transcription activity, histone composition and replication underlines the functional importance of this chromosome region for the maintenance of Bs. The conserved chromosome structure suggests a monophyletic origin of the rye B. As Bs were found in different countries, it is likely that Bs were frequently present in the seed material used in early agriculture.

CONCLUSIONS

The surprisingly conserved chromosome structure suggests that although the rye Bs experienced rapid evolution including multiple rearrangements at the early evolutionary stages, this process has slowed significantly and may have even ceased during its recent evolution.