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Human Reproduction Open 2024Is there an association between morphokinetic variables of meiotic maturation and the severity of aneuploidy following maturation (IVM) in the mouse?
STUDY QUESTION
Is there an association between morphokinetic variables of meiotic maturation and the severity of aneuploidy following maturation (IVM) in the mouse?
SUMMARY ANSWER
The severity of meiotic aneuploidy correlates with an extended time to first polar body extrusion (tPB1) and duration of meiosis I (dMI).
WHAT IS KNOWN ALREADY
Morphokinetic variables measured using time-lapse technology allow for the non-invasive evaluation of preimplantation embryo development within clinical assisted reproductive technology (ART). We recently applied this technology to monitor meiotic progression during IVM of mouse gametes. Whether there is a relationship between morphokinetic variables of meiotic progression and aneuploidy in the resulting egg has not been systematically examined at the resolution of specific chromosomes. Next-generation sequencing (NGS) is a robust clinical tool for determining aneuploidy status and has been reverse-translated in mouse blastocysts and oocytes. Therefore, we harnessed the technologies of time-lapse imaging and NGS to determine the relationship between the morphokinetics of meiotic progression and egg aneuploidy.
STUDY DESIGN SIZE DURATION
Cumulus-oocyte complexes were collected from large antral follicles from hyperstimulated CD-1 mice. Cumulus cells were removed, and spontaneous IVM was performed in the absence or presence of two doses of Nocodazole (25 or 50 nM) to induce a spectrum of spindle abnormalities and chromosome segregation errors during oocyte meiosis. Comprehensive chromosome screening was then performed in the resulting eggs, and morphokinetic variables and ploidy status were compared across experimental groups (control, n = 11; 25 nM Nocodazole, n = 13; 50 nM Nocodazole, n = 23).
PARTICIPANTS/MATERIALS SETTING METHODS
We monitored IVM in mouse oocytes using time-lapse microscopy for 16 h, and time to germinal vesicle breakdown (tGVBD), tPB1, and dMI were analyzed. Following IVM, comprehensive chromosome screening was performed on the eggs and their matched first polar bodies via adaptation of an NGS-based preimplantation genetic testing for aneuploidy (PGT-A) assay. Bioinformatics analysis was performed to align reads to the mouse genome and determine copy number-based predictions of aneuploidy. The concordance of each polar body-egg pair (reciprocal errors) was used to validate the results. Ploidy status was categorized as euploid, 1-3 chromosomal segregation errors, or ≥4 chromosomal segregation errors. Additionally, aneuploidy due to premature separation of sister chromatids (PSSC) versus non-disjunction (NDJ) was distinguished.
MAIN RESULTS AND THE ROLE OF CHANCE
We applied and validated state-of-the-art NGS technology to screen aneuploidy in individual mouse eggs and matched polar bodies at the chromosome-specific level. By performing IVM in the presence of different doses of Nocodazole, we induced a range of aneuploidy. No aneuploidy was observed in the absence of Nocodazole (0/11), whereas IVM in the presence of 25 and 50 nM Nocodazole resulted in an aneuploidy incidence of 7.69% (1/13) and 82.61% (19/23), respectively. Of the aneuploid eggs, 5% (1/20) was due to PSSC, 65% (13/20) to NDJ, and the remainder to a combination of both. There was no relationship between ploidy status and tGVBD, but tPB1 and the dMI were both significantly prolonged in eggs with reciprocal aneuploidy events compared to the euploid eggs, and this scaled with the severity of aneuploidy. Eggs with ≥4 aneuploid chromosomes had the longest tPB1 and dMI ( < 0.0001), whereas eggs with one to three aneuploid chromosomes exhibited intermediate lengths of time ( < 0.0001).
LARGE SCALE DATA
N/A.
LIMITATIONS REASONS FOR CAUTION
We used Nocodazole in this study to disrupt the meiotic spindle and induce aneuploidy in mouse oocytes. Whether the association between morphokinetic variables of meiotic progression and the severity of aneuploidy occurs with other compounds that induce chromosome segregation errors remain to be investigated. In addition, unlike mouse oocytes, human IVM requires the presence of cumulus cells, which precludes visualization of morphokinetic variables of meiotic progression. Thus, our study may have limited direct clinical translatability.
WIDER IMPLICATIONS OF THE FINDINGS
We validated NGS in mouse eggs to detect aneuploidy at a chromosome-specific resolution which greatly improves the utility of the mouse model. With a tractable and validated model system for characterizing meiotic aneuploidy, investigations into the molecular mechanisms and factors which may influence aneuploidy can be further elaborated. Time-lapse analyses of morphokinetic variables of meiotic progression may be a useful non-invasive predictor of aneuploidy severity.
STUDY FUNDING/COMPETING INTERESTS
This work was supported by the Bill & Melinda Gates Foundation (INV-003385). Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission. The authors have no conflict of interest to disclose.
PubMed: 38764910
DOI: 10.1093/hropen/hoae023 -
Plant-environment Interactions... Jun 2024Food production and food security depend on the ability of crops to cope with anthropogenic climate change and successfully produce seed. To guarantee food production... (Review)
Review
Food production and food security depend on the ability of crops to cope with anthropogenic climate change and successfully produce seed. To guarantee food production well into the future, contemporary plant scientists in Latin America must carry out research on how plants respond to environmental stressors such as temperature, drought, and salinity. This review shows the opportunities to apply these results locally and abroad and points to the gaps that still exist in terms of reproductive processes with the purpose to better link research with translational work in plant breeding and biotechnology. Suggestions are put forth to address these gaps creatively in the face of chronic low investment in science with a focus on applicability.
PubMed: 38764600
DOI: 10.1002/pei3.10143 -
American Journal of Human Genetics Jun 2024Sperm production and function require the correct establishment of DNA methylation patterns in the germline. Here, we examined the genome-wide DNA methylation changes...
Sperm production and function require the correct establishment of DNA methylation patterns in the germline. Here, we examined the genome-wide DNA methylation changes during human spermatogenesis and its alterations in disturbed spermatogenesis. We found that spermatogenesis is associated with remodeling of the methylome, comprising a global decline in DNA methylation in primary spermatocytes followed by selective remethylation, resulting in a spermatids/sperm-specific methylome. Hypomethylated regions in spermatids/sperm were enriched in specific transcription factor binding sites for DMRT and SOX family members and spermatid-specific genes. Intriguingly, while SINEs displayed differential methylation throughout spermatogenesis, LINEs appeared to be protected from changes in DNA methylation. In disturbed spermatogenesis, germ cells exhibited considerable DNA methylation changes, which were significantly enriched at transposable elements and genes involved in spermatogenesis. We detected hypomethylation in SVA and L1HS in disturbed spermatogenesis, suggesting an association between the abnormal programming of these regions and failure of germ cells progressing beyond meiosis.
Topics: Humans; Spermatogenesis; Male; DNA Methylation; Genome, Human; Spermatids; Spermatocytes; DNA Transposable Elements; Spermatozoa; Meiosis; Transcription Factors
PubMed: 38759652
DOI: 10.1016/j.ajhg.2024.04.017 -
DNA Repair Jul 2024Over the past few decades, unbiased approaches such as genetic screening and protein affinity purification have unveiled numerous proteins involved in DNA double-strand... (Review)
Review
Over the past few decades, unbiased approaches such as genetic screening and protein affinity purification have unveiled numerous proteins involved in DNA double-strand break (DSB) repair and maintaining genome stability. However, despite our knowledge of these protein factors, the underlying molecular mechanisms governing key cellular events during DSB repair remain elusive. Recent evidence has shed light on the role of non-protein factors, such as RNA, in several pivotal steps of DSB repair. In this review, we provide a comprehensive summary of these recent findings, highlighting the significance of ribosomal RNA (rRNA) as a critical mediator of DNA damage response, meiosis, and mitosis. Moreover, we discuss potential mechanisms through which rRNA may influence genome integrity.
Topics: Genomic Instability; Humans; DNA Breaks, Double-Stranded; RNA, Ribosomal; DNA Repair; Animals; Mitosis; Meiosis
PubMed: 38759435
DOI: 10.1016/j.dnarep.2024.103692 -
Current Opinion in Plant Biology Aug 2024Heat stress is one of the major constraints to plant growth and fertility. During the current climate crisis, heat waves have increased dramatically, and even more... (Review)
Review
Heat stress is one of the major constraints to plant growth and fertility. During the current climate crisis, heat waves have increased dramatically, and even more extreme conditions are predicted for the near future, considerably affecting ecosystems and seriously threatening world food security. Although heat is very well known to affect especially reproductive structures, little is known about how heat interferes with reproduction in comparison to somatic cells and tissues. Recently, the effect of heat on meiosis as a central process in sexual reproduction has been analyzed in molecular and cytological depth. Notably, these studies are not only important for applied research by laying the foundation for breeding heat-resilient crops, but also for fundamental research, revealing general regulatory mechanisms of recombination and chromosome segregation control.
Topics: Meiosis; Chromosome Segregation; Recombination, Genetic; Hot Temperature; Chromosomes, Plant
PubMed: 38749207
DOI: 10.1016/j.pbi.2024.102548 -
ELife May 2024During mammalian oocyte meiosis, spindle migration and asymmetric cytokinesis are unique steps for the successful polar body extrusion. The asymmetry defects of oocytes...
During mammalian oocyte meiosis, spindle migration and asymmetric cytokinesis are unique steps for the successful polar body extrusion. The asymmetry defects of oocytes will lead to the failure of fertilization and embryo implantation. In present study, we reported that an actin nucleating factor Formin-like 2 (FMNL2) played critical roles in the regulation of spindle migration and organelle distribution in mouse and porcine oocytes. Our results showed that FMNL2 mainly localized at the oocyte cortex and periphery of spindle. Depletion of FMNL2 led to the failure of polar body extrusion and large polar bodies in oocytes. Live-cell imaging revealed that the spindle failed to migrate to the oocyte cortex, which caused polar body formation defects, and this might be due to the decreased polymerization of cytoplasmic actin by FMNL2 depletion in the oocytes of both mice and pigs. Furthermore, mass spectrometry analysis indicated that FMNL2 was associated with mitochondria and endoplasmic reticulum (ER)-related proteins, and FMNL2 depletion disrupted the function and distribution of mitochondria and ER, showing with decreased mitochondrial membrane potential and the occurrence of ER stress. Microinjecting mRNA into FMNL2-depleted oocytes significantly rescued these defects. Thus, our results indicate that FMNL2 is essential for the actin assembly, which further involves into meiotic spindle migration and ER/mitochondria functions in mammalian oocytes.
Topics: Animals; Endoplasmic Reticulum; Meiosis; Oocytes; Formins; Mitochondria; Mice; Actins; Swine; Female; Spindle Apparatus
PubMed: 38747713
DOI: 10.7554/eLife.92732 -
Nature Genetics Jun 2024Heterosis boosts crop yield; however, harnessing additional progressive heterosis in polyploids is challenging for breeders. We bioengineered a 'mitosis instead of...
Heterosis boosts crop yield; however, harnessing additional progressive heterosis in polyploids is challenging for breeders. We bioengineered a 'mitosis instead of meiosis' (MiMe) system that generates unreduced, clonal gametes in three hybrid tomato genotypes and used it to establish polyploid genome design. Through the hybridization of MiMe hybrids, we generated '4-haplotype' plants that encompassed the complete genetics of their four inbred grandparents, providing a blueprint for exploiting polyploidy in crops.
Topics: Polyploidy; Genome, Plant; Crops, Agricultural; Solanum lycopersicum; Hybrid Vigor; Plant Breeding; Hybridization, Genetic; Genetic Engineering; Meiosis; Mitosis; Germ Cells, Plant; Germ Cells
PubMed: 38741016
DOI: 10.1038/s41588-024-01750-6 -
Proceedings of the National Academy of... May 2024Reproductive phasiRNAs (phased, small interfering RNAs) are broadly present in angiosperms and play crucial roles in sustaining male fertility. While the premeiotic...
Reproductive phasiRNAs (phased, small interfering RNAs) are broadly present in angiosperms and play crucial roles in sustaining male fertility. While the premeiotic 21-nt (nucleotides) phasiRNAs and meiotic 24-nt phasiRNA pathways have been extensively studied in maize () and rice (), a third putative category of reproductive phasiRNAs-named premeiotic 24-nt phasiRNAs-have recently been reported in barley () and wheat (). To determine whether premeiotic 24-nt phasiRNAs are also present in maize and related species and begin to characterize their biogenesis and function, we performed a comparative transcriptome and degradome analysis of premeiotic and meiotic anthers from five maize inbred lines and three teosinte species/subspecies. Our data indicate that a substantial subset of the 24-nt phasiRNA loci in maize and teosinte are already highly expressed at the premeiotic phase. The premeiotic 24-nt phasiRNAs are similar to meiotic 24-nt phasiRNAs in genomic origin and dependence on DCL5 (Dicer-like 5) for biogenesis, however, premeiotic 24-nt phasiRNAs are unique in that they are likely i) not triggered by microRNAs, ii) not loaded by AGO18 proteins, and iii) not capable of mediating precursor cleavage. In addition, we also observed a group of premeiotic 24-nt phasiRNAs in rice using previously published data. Together, our results indicate that the premeiotic 24-nt phasiRNAs constitute a unique class of reproductive phasiRNAs and are present more broadly in the grass family (Poaceae) than previously known.
Topics: Zea mays; Meiosis; RNA, Plant; Gene Expression Regulation, Plant; RNA, Small Interfering; Transcriptome; Oryza
PubMed: 38739785
DOI: 10.1073/pnas.2402285121 -
PLoS Computational Biology May 2024During meiosis, pairing of homologous chromosomes (homologs) ensures the formation of haploid gametes from diploid precursor cells, a prerequisite for sexual...
During meiosis, pairing of homologous chromosomes (homologs) ensures the formation of haploid gametes from diploid precursor cells, a prerequisite for sexual reproduction. Pairing during meiotic prophase I facilitates crossover recombination and homolog segregation during the ensuing reductional cell division. Mechanisms that ensure stable homolog alignment in the presence of an excess of non-homologous chromosomes have remained elusive, but rapid chromosome movements appear to play a role in the process. Apart from homolog attraction, provided by early intermediates of homologous recombination, dissociation of non-homologous associations also appears to contribute to homolog pairing, as suggested by the detection of stable non-homologous chromosome associations in pairing-defective mutants. Here, we have developed an agent-based model for homolog pairing derived from the dynamics of a naturally occurring chromosome ensemble. The model simulates unidirectional chromosome movements, as well as collision dynamics determined by attractive and repulsive forces arising from close-range physical interactions. Chromosome number and size as well as movement velocity and repulsive forces are identified as key factors in the kinetics and efficiency of homologous pairing in addition to homolog attraction. Dissociation of interactions between non-homologous chromosomes may contribute to pairing by crowding homologs into a limited nuclear area thus creating preconditions for close-range homolog attraction. Incorporating natural chromosome lengths, the model accurately recapitulates efficiency and kinetics of homolog pairing observed for wild-type and mutant meiosis in budding yeast, and can be adapted to nuclear dimensions and chromosome sets of other organisms.
Topics: Meiosis; Chromosome Pairing; Models, Genetic; Saccharomyces cerevisiae; Chromosomes, Fungal; Cell Nucleus; Computer Simulation; Computational Biology
PubMed: 38739641
DOI: 10.1371/journal.pcbi.1011416 -
BMC Plant Biology May 2024Unreduced gamete formation during meiosis plays a critical role in natural polyploidization. However, the unreduced gamete formation mechanisms in Triticum...
BACKGROUND
Unreduced gamete formation during meiosis plays a critical role in natural polyploidization. However, the unreduced gamete formation mechanisms in Triticum turgidum-Aegilops umbellulata triploid F hybrid crosses and the chromsome numbers and compostions in T. turgidum-Ae. umbellulata F still not known.
RESULTS
In this study, 11 T.turgidum-Ae. umbellulata triploid F hybrid crosses were produced by distant hybridization. All of the triploid F hybrids had 21 chromosomes and two basic pathways of meiotic restitution, namely first-division restitution (FDR) and single-division meiosis (SDM). Only FDR was found in six of the 11 crosses, while both FDR and SDM occurred in the remaining five crosses. The chromosome numbers in the 127 selfed F seeds from the triploid F hybrid plants of 10 crosses (no F seeds for STU 16) varied from 35 to 43, and the proportions of euploid and aneuploid F plants were 49.61% and 50.39%, respectively. In the aneuploid F plants, the frequency of chromosome loss/gain varied among genomes. The chromosome loss of the U genome was the highest (26.77%) among the three genomes, followed by that of the B (22.83%) and A (11.81%) genomes, and the chromosome gain for the A, B, and U genomes was 3.94%, 3.94%, and 1.57%, respectively. Of the 21 chromosomes, 7U (16.54%), 5 A (3.94%), and 1B (9.45%) had the highest loss frequency among the U, A, and B genomes. In addition to chromosome loss, seven chromosomes, namely 1 A, 3 A, 5 A, 6 A, 1B, 1U, and 6U, were gained in the aneuploids.
CONCLUSION
In the aneuploid F plants, the frequency of chromosome loss/gain varied among genomes, chromsomes, and crosses. In addition to variations in chromosome numbers, three types of chromosome translocations including 3UL·2AS, 6UL·1AL, and 4US·6AL were identified in the F plants. Furthermore, polymorphic fluorescence in situ hybridization karyotypes for all the U chromosomes were also identified in the F plants when compared with the Ae. umbellulata parents. These results provide useful information for our understanding the naturally occurred T. turgidum-Ae. umbellulata amphidiploids.
Topics: Chromosomal Instability; Hybridization, Genetic; Triticum; Chromosomes, Plant; Aegilops; Meiosis; Triploidy; Polyploidy; Genome, Plant
PubMed: 38735929
DOI: 10.1186/s12870-024-05110-8