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Current Issues in Molecular Biology May 2024Sexual maturation of Atlantic salmon males is marked by dramatic endocrine changes and rapid growth of the testes, resulting in an increase in the gonad somatic index...
Sexual maturation of Atlantic salmon males is marked by dramatic endocrine changes and rapid growth of the testes, resulting in an increase in the gonad somatic index (GSI). We examined the association of gonadal growth with serum sex steroids, as well as pituitary and testicular gene expression levels, which were assessed with a DNA oligonucleotide microarray. The testes transcriptome was stable in males with a GSI < 0.08% despite the large difference between the smallest and the largest gonads. Fish with a GSI ≥ 0.23% had 7-17 times higher serum levels of five male steroids and a 2-fold increase in progesterone, without a change in cortisol and related steroids. The pituitary transcriptome showed an upregulation of the hormone-coding genes that control reproduction and behavior, and structural rearrangement was indicated by the genes involved in synaptic transmission and the differentiation of neurons. The observed changes in the abundance of testicular transcripts were caused by the regulation of transcription and/or disproportional growth, with a greater increase in the germinative compartment. As these factors could not be separated, the transcriptome results are presented as higher or lower specific activities (HSA and LSA). LSA was observed in 4268 genes, including many genes involved in various immune responses and developmental processes. LSA also included genes with roles in female reproduction, germinal cell maintenance and gonad development, responses to endocrine and neural regulation, and the biosynthesis of sex steroids. Two functional groups prevailed among HSA: structure and activity of the cilia (95 genes) and meiosis (34 genes). The puberty of A. salmon testis is marked by the predominance of spermatogenesis, which displaces other processes; masculinization; and the weakening of external regulation. Results confirmed the known roles of many genes involved in reproduction and pointed to uncharacterized genes that deserve attention as possible regulators of sexual maturation.
PubMed: 38920991
DOI: 10.3390/cimb46060319 -
Proceedings of the National Academy of... Jul 2024A dispersed cytoplasmic distribution of mitochondria is a hallmark of normal cellular organization. Here, we have utilized the expression of exogenous in mouse oocytes...
A dispersed cytoplasmic distribution of mitochondria is a hallmark of normal cellular organization. Here, we have utilized the expression of exogenous in mouse oocytes and embryos to disrupt the dispersed distribution of mitochondria by driving them into a large cytoplasmic aggregate. Our findings reveal that aggregated mitochondria have minimal impact on asymmetric meiotic cell divisions of the oocyte. In contrast, aggregated mitochondria during the first mitotic division result in daughter cells with unequal sizes and increased micronuclei. Further, in two-cell embryos, microtubule-mediated centering properties of the mitochondrial aggregate prevent nuclear centration, distort nuclear shape, and inhibit DNA synthesis and the onset of embryonic transcription. These findings demonstrate the motor protein-mediated distribution of mitochondria throughout the cytoplasm is highly regulated and is an essential feature of cytoplasmic organization to ensure optimal cell function.
Topics: Animals; Mitochondria; Blastocyst; Mice; Cell Nucleus; Oocytes; Female; Embryonic Development; Microtubules; Mitosis; Meiosis
PubMed: 38917013
DOI: 10.1073/pnas.2317316121 -
Cell Death Discovery Jun 2024Despite the advances in the understanding of reproductive physiology, the mechanisms underlying ovarian aging are still not deciphered. Recent research found an...
Despite the advances in the understanding of reproductive physiology, the mechanisms underlying ovarian aging are still not deciphered. Recent research found an association between impaired ATM-mediated DNA double-strand break (DSB) repair mechanisms and oocyte aging. However, direct evidence connecting ATM-mediated pathway function decline and impaired oocyte quality is lacking. The objective of this study was to determine the role of ATM-mediated DNA DSB repair in the maintenance of oocyte quality in a mouse oocyte knockdown model. Gene interference, in vitro culture, parthenogenesis coupled with genotoxicity assay approaches, as well as molecular cytogenetic analyses based upon next-generation sequencing, were used to test the hypothesis that intact ATM function is critical in the maintenance of oocyte quality. We found that ATM knockdown impaired oocyte quality, resulting in poor embryo development. ATM knockdown significantly lowered or blocked the progression of meiosis in vitro, as well as retarding and reducing embryo cleavage after parthenogenesis. After ATM knockdown, all embryos were of poor quality, and none reached the blastocyst stage. ATM knockdown was also associated with an increased aneuploidy rate compared to controls. Finally, ATM knockdown increased the sensitivity of the oocytes to a genotoxic active metabolite of cyclophosphamide, with increased formation of DNA DSBs, reduced survival, and earlier apoptotic death compared to controls. These findings suggest a key role for ATM in maintaining oocyte quality and resistance to genotoxic stress, and that the previously observed age-induced decline in oocyte ATM function may be a prime factor contributing to oocyte aging.
PubMed: 38914566
DOI: 10.1038/s41420-024-02041-z -
PLoS Genetics Jun 2024Precise regulation of chromosome dynamics in the germline is essential for reproductive success across species. Yet, the mechanisms underlying meiotic chromosomal events...
Precise regulation of chromosome dynamics in the germline is essential for reproductive success across species. Yet, the mechanisms underlying meiotic chromosomal events such as homolog pairing and chromosome segregation are not fully understood in many species. Here, we employ Oligopaint DNA FISH to investigate mechanisms of meiotic homolog pairing and chromosome segregation in the holocentric pantry moth, Plodia interpunctella, and compare our findings to new and previous studies in the silkworm moth, Bombyx mori, which diverged from P. interpunctella over 100 million years ago. We find that pairing in both Bombyx and Plodia spermatogenesis is initiated at gene-rich chromosome ends. Additionally, both species form rod shaped cruciform-like bivalents at metaphase I. However, unlike the telomere-oriented chromosome segregation mechanism observed in Bombyx, Plodia can orient bivalents in multiple different ways at metaphase I. Surprisingly, in both species we find that kinetochores consistently assemble at non-telomeric loci toward the centers of chromosomes regardless of where chromosome centers are located in the bivalent. Additionally, sister kinetochores do not seem to be paired in these species. Instead, four distinct kinetochores are easily observed at metaphase I. Despite this, we find clear end-on microtubule attachments and not lateral microtubule attachments connecting these separated kinetochores to the meiotic spindle. These findings challenge the classical view of segregation where paired, poleward-facing kinetochores are required for accurate homolog separation in meiosis I. Our studies here highlight the importance of exploring fundamental processes in non-model systems, as employing novel organisms can lead to the discovery of novel biology.
PubMed: 38913752
DOI: 10.1371/journal.pgen.1011329 -
Methods in Molecular Biology (Clifton,... 2024Chromosome banding can be defined as the lengthwise variation in staining properties along a chromosome stained with a dye. Chromosome banding became more practical in...
Chromosome banding can be defined as the lengthwise variation in staining properties along a chromosome stained with a dye. Chromosome banding became more practical in the early 1970s and is an essential technique used in karyotyping to identify human chromosomes for both clinical and research purposes. Most importantly, karyotyping is now considered a mandatory investigation of all newly diagnosed leukemias. Some banding methods, such as Giemsa (G)-, reverse (R)-, and centromere (C)-banding, still contribute greatly by being used as a routine procedure in clinical cytogenetic laboratory nowadays. Each chromosome has a unique sequence of bar code-like stripes, allowing the identification of individual homologues and the recognition of structural abnormalities through analyzing the disruption of the normal banding pattern at specific landmarks, regions, and bands as described in the ideogram. Since the quality of metaphases obtained from malignant cells is generally inferior to normal constitutional cells for karyotyping, a practical and accurate chromosome identification training guide is indispensable for a trainee or newly employed cytogenetic technologist in a cancer cytogenetic laboratory. The most common and currently used banding methods and chromosome recognition guide for distinguishable bands of each chromosome are described in detail in this chapter with an aim to facilitate quick and accurate karyotyping in cancer cells.
Topics: Humans; Chromosome Banding; Karyotyping; Chromosomes, Human; Metaphase
PubMed: 38913307
DOI: 10.1007/978-1-0716-3946-7_7 -
Methods in Molecular Biology (Clifton,... 2024Based on classical karyotyping, structural genome variations (SVs) have generally been considered to be either "simple" (with one or two breakpoints) or "complex" (with... (Review)
Review
Based on classical karyotyping, structural genome variations (SVs) have generally been considered to be either "simple" (with one or two breakpoints) or "complex" (with more than two breakpoints). Studying the breakpoints of SVs at nucleotide resolution revealed additional, subtle structural variations, such that even "simple" SVs turned out to be "complex." Genome-wide sequencing methods, such as fosmid and paired-end mapping, short-read and long-read whole genome sequencing, and single-molecule optical mapping, also indicated that the number of SVs per individual was considerably larger than expected from karyotyping and high-resolution chromosomal array-based studies. Interestingly, SVs were detected in studies of cohorts of individuals without clinical phenotypes. The common denominator of all SVs appears to be a failure to accurately repair DNA double-strand breaks (DSBs) or to halt cell cycle progression if DSBs persist. This review discusses the various DSB response mechanisms during the mitotic cell cycle and during meiosis and their regulation. Emphasis is given to the molecular mechanisms involved in the formation of translocations, deletions, duplications, and inversions during or shortly after meiosis I. Recently, CRISPR-Cas9 studies have provided unexpected insights into the formation of translocations and chromothripsis by both breakage-fusion-bridge and micronucleus-dependent mechanisms.
Topics: Humans; Genomic Structural Variation; DNA Breaks, Double-Stranded; Meiosis; Karyotyping; CRISPR-Cas Systems; Animals
PubMed: 38913302
DOI: 10.1007/978-1-0716-3946-7_2 -
Reproductive Toxicology (Elmsford, N.Y.) Jun 2024Infertility affects ∼12 % of couples, with environmental chemical exposure as a potential contributor. Of the chemicals that are actively manufactured, very few are...
Infertility affects ∼12 % of couples, with environmental chemical exposure as a potential contributor. Of the chemicals that are actively manufactured, very few are assessed for reproductive health effects. Rodents are commonly used to evaluate reproductive effects, which is both costly and time consuming. Thus, there is a pressing need for rapid methods to test a broader range of chemicals. Here, we developed a strategy to evaluate large numbers of chemicals for reproductive toxicity via a yeast, S. cerevisiae high-throughput assay to assess gametogenesis as a potential new approach method (NAM). By simultaneously assessing chemicals for growth effects, we can distinguish if a chemical affects gametogenesis only, proliferative growth only or both. We identified a well-known mammalian reproductive toxicant, bisphenol A (BPA) and ranked 19 BPA analogs for reproductive harm. By testing mixtures of BPA and its analogs, we found that BPE and 17 β-estradiol each together with BPA showed synergistic effects that worsened reproductive outcome. We examined an additional 179 environmental chemicals including phthalates, pesticides, quaternary ammonium compounds and per- and polyfluoroalkyl substances and found 57 with reproductive effects. Many of the chemicals were found to be strong reproductive toxicants that have yet to be tested in mammals. Chemicals having affect before meiosis I division vs. meiosis II division were identified for 16 gametogenesis-specific chemicals. Finally, we demonstrate that in general yeast reproductive toxicity correlates well with published reproductive toxicity in mammals illustrating the promise of this NAM to quickly assess chemicals to prioritize the evaluation for human reproductive harm.
PubMed: 38906490
DOI: 10.1016/j.reprotox.2024.108630 -
Developmental Cell Jun 2024Sexually reproducing eukaryotes employ a developmentally regulated cell division program-meiosis-to generate haploid gametes from diploid germ cells. To understand how...
Sexually reproducing eukaryotes employ a developmentally regulated cell division program-meiosis-to generate haploid gametes from diploid germ cells. To understand how gametes arise, we generated a proteomic census encompassing the entire meiotic program of budding yeast. We found that concerted waves of protein expression and phosphorylation modify nearly all cellular pathways to support meiotic entry, meiotic progression, and gamete morphogenesis. Leveraging this comprehensive resource, we pinpointed dynamic changes in mitochondrial components and showed that phosphorylation of the FF-ATP synthase complex is required for efficient gametogenesis. Furthermore, using cryoET as an orthogonal approach to visualize mitochondria, we uncovered highly ordered filament arrays of Ald4, a conserved aldehyde dehydrogenase that is highly expressed and phosphorylated during meiosis. Notably, phosphorylation-resistant mutants failed to accumulate filaments, suggesting that phosphorylation regulates context-specific Ald4 polymerization. Overall, this proteomic census constitutes a broad resource to guide the exploration of the unique sequence of events underpinning gametogenesis.
PubMed: 38906138
DOI: 10.1016/j.devcel.2024.05.025 -
Cell Jun 2024Gamete formation and subsequent offspring development often involve extended phases of suspended cellular development or even dormancy. How cells adapt to recover and...
Gamete formation and subsequent offspring development often involve extended phases of suspended cellular development or even dormancy. How cells adapt to recover and resume growth remains poorly understood. Here, we visualized budding yeast cells undergoing meiosis by cryo-electron tomography (cryoET) and discovered elaborate filamentous assemblies decorating the nucleus, cytoplasm, and mitochondria. To determine filament composition, we developed a "filament identification" (FilamentID) workflow that combines multiscale cryoET/cryo-electron microscopy (cryoEM) analyses of partially lysed cells or organelles. FilamentID identified the mitochondrial filaments as being composed of the conserved aldehyde dehydrogenase Ald4 and the nucleoplasmic/cytoplasmic filaments as consisting of acetyl-coenzyme A (CoA) synthetase Acs1. Structural characterization further revealed the mechanism underlying polymerization and enabled us to genetically perturb filament formation. Acs1 polymerization facilitates the recovery of chronologically aged spores and, more generally, the cell cycle re-entry of starved cells. FilamentID is broadly applicable to characterize filaments of unknown identity in diverse cellular contexts.
Topics: Aldehyde Dehydrogenase; Cell Nucleus; Coenzyme A Ligases; Cryoelectron Microscopy; Cytoplasm; Electron Microscope Tomography; Gametogenesis; Meiosis; Mitochondria; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Spores, Fungal; Models, Molecular; Protein Structure, Quaternary
PubMed: 38906101
DOI: 10.1016/j.cell.2024.04.026 -
BioRxiv : the Preprint Server For... Feb 2024During meiosis, homologous chromosomes segregate so that alleles are transmitted equally to haploid gametes, following Mendel's Law of Segregation. However, some selfish...
During meiosis, homologous chromosomes segregate so that alleles are transmitted equally to haploid gametes, following Mendel's Law of Segregation. However, some selfish genetic elements drive in meiosis to distort the transmission ratio and increase their representation in gametes. The established paradigms for drive are fundamentally different for female vs male meiosis. In male meiosis, selfish elements typically kill gametes that do not contain them. In female meiosis, killing is predetermined, and selfish elements bias their segregation to the single surviving gamete (i.e., the egg in animal meiosis). Here we show that a selfish element on mouse chromosome 2, , drives using a hybrid mechanism in female meiosis, incorporating elements of both male and female drivers. If is destined for the polar body, it manipulates segregation to sabotage the egg by causing aneuploidy that is subsequently lethal in the embryo, so that surviving progeny preferentially contain . In heterozygous females, orients randomly on the metaphase spindle but lags during anaphase and preferentially remains in the egg, regardless of its initial orientation. Thus, the egg genotype is either euploid with or aneuploid with both homologs of chromosome 2, with only the former generating viable embryos. Consistent with this model, heterozygous females produce eggs with increased aneuploidy for chromosome 2, increased embryonic lethality, and increased transmission of . In contrast to a male meiotic driver, which kills its sister gametes produced as daughter cells in the same meiosis, eliminates "cousins" produced from meioses in which it should have been excluded from the egg.
PubMed: 38903120
DOI: 10.1101/2024.02.22.581453