bims-cebooc Biomed News
on Cell biology of oocytes
Issue of 2024–11–03
twelve papers selected by
Gabriele Zaffagnini, Universität zu Köln
  1. COX15 deficiency causes oocyte ferroptosis.
  2. Maternal genetic variants in kinesin motor domains prematurely increase egg aneuploidy.
  3. EB-SUN, a New Microtubule Plus-End Tracking Protein in Drosophila.
  4. An interkinetic envelope surrounds chromosomes between meiosis I and II in C. elegans oocytes.
  5. Exceptional longevity of mammalian ovarian and oocyte macromolecules throughout the reproductive lifespan.
  6. Diffusion within the synaptonemal complex can account for signal transduction along meiotic chromosomes.
  7. Dynamic protein assembly and architecture of the large solitary membraneless organelle during germline development in the wasp Nasonia vitripennis.
  8. The mechanical journey of primordial germ cells.
  9. Stereological study of organelle distribution in human mature oocytes.
  10. PI3K/AKT signaling controls ICM maturation and proper epiblast and primitive endoderm specification in mice.
  11. Rat copper transport protein 2 (CTR2) is involved in fertilization through interaction with IZUMO1 and JUNO.
  12. Evidence of apoptosis as an early event leading to cyclophosphamide-induced primordial follicle depletion in a prepubertal mouse model.
  1. Proc Natl Acad Sci U S A. 2024 Nov 05. 121(45): e2406174121
    COX15 deficiency causes oocyte ferroptosis.
    Zhihua Zhang, Ran Yu, Qiuwen Shi, Zhi-Jing Wu, Qingchun Li, Jian Mu, Biaobang Chen, Juanzi Shi, Renmin Ni, Ling Wu, Qiaoli Li, Jing Fu, Rong Li, Xiaoxi Sun, Jiucun Wang, Lin He, Yanping Kuang, Qing Sang, Lei Wang.
      Mitochondria play diverse roles in mammalian physiology. The architecture, activity, and physiological functions of mitochondria in oocytes are largely different from those in somatic cells, but the mitochondrial proteins related to oocyte quality and reproductive longevity remain largely unknown. Here, using whole-exome sequencing data from 1,024 women (characterized by oocyte maturation arrest and degenerated or morphologically abnormal oocytes) and 2,868 healthy controls, we performed a population and gene-based burden test for mitochondrial genes and identified a candidate gene, cytochrome c oxidase assembly protein 15 (COX15). We report that biallelic COX15 pathogenic variants cause human oocyte ferroptosis and female infertility in a recessive inheritance pattern. COX15 variants impaired mitochondrial respiration in Saccharomyces cerevisiae and led to reduced protein levels in HeLa cells. Oocyte-specific deletion of Cox15 led to impaired Fe2+ and reactive oxygen species homeostasis that caused mitochondrial dysfunction and ultimately sensitized oocytes to ferroptosis. In addition, ferrostatin-1 (an inhibitor of ferroptosis) could rescue the oocyte ferroptosis phenotype in vitro and ex vivo. Our findings not only provide a genetic diagnostic marker for oocyte development defects but also expand the spectrum of mitochondrial disorders to female infertility and contribute to unique insights into the role of ferroptosis in human oocyte defects.
    Keywords:  COX15 deficiency; female infertility; ferroptosis; mitochondrial disorders; oocyte defects
    DOI:  https://doi.org/10.1073/pnas.2406174121
  2. Proc Natl Acad Sci U S A. 2024 Nov 05. 121(45): e2414963121
    Maternal genetic variants in kinesin motor domains prematurely increase egg aneuploidy.
    Leelabati Biswas, Katarzyna M Tyc, Mansour Aboelenain, Siqi Sun, Iva Dundović, Kruno Vukušić, Jason Liu, Vanessa Guo, Min Xu, Richard T Scott, Xin Tao, Iva M Tolić, Jinchuan Xing, Karen Schindler.
      The female reproductive lifespan is highly dependent on egg quality, especially the presence of a normal number of chromosomes in an egg, known as euploidy. Mistakes in meiosis leading to egg aneuploidy are frequent in humans. Yet, knowledge of the precise genetic landscape that causes egg aneuploidy in women is limited, as phenotypic data on the frequency of human egg aneuploidy are difficult to obtain and therefore absent in public genetic datasets. Here, we identify genetic determinants of reproductive aging via egg aneuploidy in women using a biobank of individual maternal exomes linked with maternal age and embryonic aneuploidy data. Using the exome data, we identified 404 genes bearing variants enriched in individuals with pathologically elevated egg aneuploidy rates. Analysis of the gene ontology and protein-protein interaction network implicated genes encoding the kinesin protein family in egg aneuploidy. We interrogate the causal relationship of the human variants within candidate kinesin genes via experimental perturbations and demonstrate that motor domain variants increase aneuploidy in mouse oocytes. Finally, using a knock-in mouse model, we validate that a specific variant in kinesin KIF18A accelerates reproductive aging and diminishes fertility. These findings reveal additional functional mechanisms of reproductive aging and shed light on how genetic variation underlies individual heterogeneity in the female reproductive lifespan, which might be leveraged to predict reproductive longevity. Together, these results lay the groundwork for the noninvasive biomarkers for egg quality, a first step toward personalized fertility medicine.
    Keywords:  aneuploidy; infertility; kinesin; meiosis; oocyte
    DOI:  https://doi.org/10.1073/pnas.2414963121
  3. Mol Biol Cell. 2024 Oct 30. mbcE24090402
    EB-SUN, a New Microtubule Plus-End Tracking Protein in Drosophila.
    Sun K Kim, Stephen L Rogers, Wen Lu, Brad S Lee, Vladimir I Gelfand.
      Microtubule (MT) regulation is essential for oocyte development. In Drosophila, MT stability, polarity, abundance, and orientation undergo dynamic changes across developmental stages. In our effort to identify novel microtubule-associated proteins (MAPs) that regulate MTs in the Drosophila ovary, we identified a previously uncharacterized gene, CG18190, encoding a novel MT end-binding (EB) protein, which we propose to name EB-SUN. We show that EB-SUN colocalizes with EB1 at growing microtubule plus-ends in Drosophila S2 cells. Tissue-specific and developmental expression profiles from Paralog Explorer reveal that EB-SUN is predominantly expressed in the ovary and early embryos, while EB1 is ubiquitously expressed. Furthermore, as early as oocyte determination, EB-SUN comets are highly concentrated in oocytes during oogenesis. EB-SUN knockout (KO) results in a decrease in MT density at the onset of mid-oogenesis (Stage 7) and delays oocyte growth during late mid-oogenesis (Stage 9). Combining EB-SUN KO with EB1 knockdown (KD) in germ cells significantly further reduced MT density at Stage 7. Hatching assays of single protein depletion reveal distinct roles for EB-SUN and EB1 in early embryogenesis, likely due to differences in expression and binding partners. Notably, all eggs from EB-SUN KO/EB1 KD females fail to hatch, suggesting partial redundancy between these proteins. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].
    DOI:  https://doi.org/10.1091/mbc.E24-09-0402
  4. bioRxiv. 2024 Oct 21. pii: 2024.10.19.619195. [Epub ahead of print]
    An interkinetic envelope surrounds chromosomes between meiosis I and II in C. elegans oocytes.
    Layla El Mossadeq, Laura Bellutti, Rémi Le Borgne, Julie C Canman, Lionel Pintard, Jean-Marc Verbavatz, Peter Askjaer, Julien Dumont.
      At the end of cell division, the nuclear envelope reassembles around the decondensing chromosomes. Female meiosis culminates in two consecutive cell divisions of the oocyte, meiosis I and II, which are separated by a brief transition phase known as interkinesis. Due to the absence of chromosome decondensation and the suppression of genome replication during interkinesis, it has been widely assumed that the nuclear envelope does not reassemble between meiosis I and II. By analyzing interkinesis in C. elegans oocytes, we instead show that an atypical structure made of two lipid bilayers, which we termed the interkinetic envelope, surrounds the surface of the segregating chromosomes. The interkinetic envelope shares common features with the nuclear envelope but also exhibits specific characteristics that distinguish it, including its lack of continuity with the endoplasmic reticulum, unique protein composition, assembly mechanism, and function in chromosome segregation. These distinct attributes collectively define the interkinetic envelope as a unique and specialized structure that has been previously overlooked.
    DOI:  https://doi.org/10.1101/2024.10.19.619195
  5. Elife. 2024 Oct 31. pii: RP93172. [Epub ahead of print]13
    Exceptional longevity of mammalian ovarian and oocyte macromolecules throughout the reproductive lifespan.
    Ewa K Bomba-Warczak, Karen M Velez, Luhan T Zhou, Christelle Guillermier, Seby Edassery, Matthew L Steinhauser, Jeffrey N Savas, Francesca E Duncan.
      The mechanisms contributing to age-related deterioration of the female reproductive system are complex, however aberrant protein homeostasis is a major contributor. We elucidated exceptionally stable proteins, structures, and macromolecules that persist in mammalian ovaries and gametes across the reproductive lifespan. Ovaries exhibit localized structural and cell-type-specific enrichment of stable macromolecules in both the follicular and extrafollicular environments. Moreover, ovaries and oocytes both harbor a panel of exceptionally long-lived proteins, including cytoskeletal, mitochondrial, and oocyte-derived proteins. The exceptional persistence of these long-lived molecules suggest a critical role in lifelong maintenance and age-dependent deterioration of reproductive tissues.
    Keywords:  cell biology; long-lived proteins; mass spectrometry imaging; mouse; oocyte; ovaries; proteomics; reproductive aging
    DOI:  https://doi.org/10.7554/eLife.93172
  6. Mol Biol Cell. 2024 Oct 30. mbcE24050225
    Diffusion within the synaptonemal complex can account for signal transduction along meiotic chromosomes.
    Lexy von Diezmann, Chloe Bristow, Ofer Rog.
      Meiotic chromosomes efficiently transduce information along their length to regulate the distribution of genetic exchanges (crossovers). However, the mode of signal transduction remains unknown. A conserved protein interface called the synaptonemal complex forms between the parental chromosomes. The synaptonemal complex exhibits liquid-like behaviors, suggesting that the diffusion of signaling molecules along its length could coordinate crossover formation. Here, we directly test the feasibility of such a mechanism by tracking a component of the synaptonemal complex (SYP-3) and a conserved regulator of exchanges (ZHP-3) in live C. elegans gonads. While we find that both proteins diffuse within the synaptonemal complex, ZHP-3 diffuses 4- and 9-fold faster than SYP-3 before and after crossover designation, respectively. We use these measurements to parameterize a physical model for signal transduction. We find that ZHP-3, but not SYP-3, can explore the lengths of chromosomes on the time scale of crossover designation, consistent with a role in the spatial regulation of exchanges. Given the conservation of ZHP-3 paralogs across eukaryotes, we propose that diffusion along the synaptonemal complex may be a conserved mechanism of meiotic regulation. More broadly, our work explores how diffusion compartmentalized by condensates could regulate crucial chromosomal functions.
    DOI:  https://doi.org/10.1091/mbc.E24-05-0225
  7. Development. 2024 Oct 26. pii: dev.202877. [Epub ahead of print]
    Dynamic protein assembly and architecture of the large solitary membraneless organelle during germline development in the wasp Nasonia vitripennis.
    Kabita Kharel, Samuel J Tindell, Allie Kemph, Ryan Schmidtke, Emma Alexander, Jeremy A Lynch, Alexey L Arkov.
      Throughout metazoa, germ cells assemble RNA-protein organelles (germ granules). In Drosophila ovaries, perinuclear nuage forms in the nurse cells, while compositionally similar polar granules form in the oocyte. A similar system appears to exist in the distantly related (∼350 million years) wasp Nasonia, with some surprising divergences. Nuage is similarly formed in Nasonia, except that anterior nurse cells accumulate significantly more nuage, in association with high levels of DNA double-strand breaks, suggesting that increased transposon activity in anterior is silenced by high nuage levels. In the oocyte, the germ plasm forms a single granule that is 40 times larger than a homologous Drosophila polar granule. While conserved germ granule proteins are recruited to the oosome, they show unusual localization: Tudor protein forms a shell encapsulating the embryonic oosome, while small Oskar/Vasa/Aubergine granules coalesce interiorly. Wasp Vasa itself is unusual since it has an alternative splice form that includes a novel nucleoporin-like phenylalanine-glycine repeat domain. Our work is consistent with the high degree of evolutionary plasticity of membraneless organelles and describes new experimental model and resources to study biomolecular condensates.
    Keywords:   Nasonia ; Germline development; Membraneless organelles; Oskar; Tudor domain; Vasa
    DOI:  https://doi.org/10.1242/dev.202877
  8. Am J Physiol Cell Physiol. 2024 Oct 28.
    The mechanical journey of primordial germ cells.
    Malhar Chitnis, Xu Gao, Jennifer Marlena, Andrew Holle.
      Primordial germ cells (PGCs) are the earliest progenitors of germline cells of the gonads in animals. The tissues that arise from primordial germ cells give rise to the male as well as female gametes and are thus responsible for transmitting genetic information to subsequent generations. Their development from single cells to fully formed tissues has thus been of great importance. In most higher animals, PGCs are initially specified at a site away from the gonads. They then migrate across multiple tissue contexts to reach a mesodermal mass of cells called the genital ridge, where they associate with somatic cells to form the sex-specific reproductive organs. This migratory behavior has been studied extensively to identify the various tissues PGCs interact with and how this might affect their development. A crucial point overlooked by classical studies has been the physical environment experienced by PGCs as they migrate and the mechanical challenges they might encounter. It has long been understood that migrating cells can sense and adapt to physical forces around them via a variety of mechanisms. Studies have also shown that these mechanical signals can guide stem cell fate. In this review, we summarize the mechanical microenvironment of migrating PGCs in different organisms. We describe how cells can adapt to this environment and how this adaptation can influence cell fate. We propose that mechanical signals play a crucial role in normal development of the germline and shed light on this unexplored area of developmental biology.
    Keywords:  Confinement; Differentiation; Mechanobiology; Primordial Germ Cells; Stem Cells
    DOI:  https://doi.org/10.1152/ajpcell.00404.2024
  9. Sci Rep. 2024 10 28. 14(1): 25816
    Stereological study of organelle distribution in human mature oocytes.
    Tânia Santos, Ana S Pires-Luís, Ana Margarida Calado, Elsa Oliveira, Mariana Cunha, Joaquina Silva, Paulo Viana, José Teixeira-da-Silva, Cristiano Oliveira, Alberto Barros, Rosália Sá, Mário Sousa.
      The ultrastructure of human oocytes has been described only qualitatively. To offer a precise organelle spatial distribution and organelle volume during the main maturation stages, we previously conducted stereological studies on prophase-I (GV) and metaphase-I (MI) oocytes, and here we present results on metaphase-II (MII) oocytes. Five donor oocytes from different donors were processed for transmission electron microscopy, and quantification of organelle distribution was performed using point-counting stereology. Statistical tests compared the means of the relative volumes occupied by organelles among oocyte regions. The most abundant organelles were elements of the smooth endoplasmic reticulum (SER), such as SER small vesicles, SER medium vesicles, SER large vesicles and SER isolated tubules, along with mitochondria, followed by SER tubular aggregates, cortical vesicles and lysosomes. Significant differences between oocyte regions were found for lysosomes, cortical vesicles and SER large vesicles. Comparisons of MII oocytes to previous findings in GV and MI oocytes evidenced specific patterns of organelle distribution and relative volumes. This final evaluation thus enables to track organelle spatial reorganization across oocyte stages, which, in addition to gathered knowledge, may be useful to assist in improvements of stimulation protocols, in-vitro maturation media and cryopreservation techniques.
    Keywords:  Human donor oocytes; Mature oocytes; Oocyte cytoplasmic maturation; Oocytes; Stereology; Ultrastructure
    DOI:  https://doi.org/10.1038/s41598-024-76893-x
  10. Dev Cell. 2024 Oct 22. pii: S1534-5807(24)00601-4. [Epub ahead of print]
    PI3K/AKT signaling controls ICM maturation and proper epiblast and primitive endoderm specification in mice.
    Anna Geiselmann, Adèle Micouin, Sandrine Vandormael-Pournin, Vincent Laville, Almira Chervova, Sébastien Mella, Pablo Navarro, Michel Cohen-Tannoudji.
      The inner cell mass (ICM) of early mouse embryos is specified into epiblast (Epi) and primitive endoderm (PrE) lineages during blastocyst formation. The antagonistic transcription factors (TFs) NANOG and GATA-binding protein 6 (GATA6) in combination with fibroblast growth factor (FGF)/extracellular-signal-regulated kinase (ERK) signaling are central actors in ICM fate choice. However, what initiates the specification of ICM progenitors into Epi or PrE and whether other factors are involved in this process has not been fully understood yet. Here, we show that phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) is constitutively active during preimplantation development. Using pharmacological inhibition, we demonstrate that PI3K/AKT enables the formation of a functional ICM capable of giving rise to both the Epi and the PrE: it maintains the expression of the TF NANOG, which specifies the Epi, and confers responsiveness to FGF4, which is essential for PrE specification. Our work thus identifies PI3K/AKT signaling as an upstream regulator controlling the molecular events required for both Epi and PrE specification.
    Keywords:  FGF4; FOXO3; GSK3; NANOG; epiblast; inner cell mass; lineage specification; mTOR; mouse preimplantation embryo; primitive endoderm
    DOI:  https://doi.org/10.1016/j.devcel.2024.10.001
  11. Theriogenology. 2024 Oct 21. pii: S0093-691X(24)00430-8. [Epub ahead of print]231 160-170
    Rat copper transport protein 2 (CTR2) is involved in fertilization through interaction with IZUMO1 and JUNO.
    Rina Su, Ruizhuo Liu, Yangyang Sun, Huimin Su, Wanjin Xing.
      In mammalian reproduction, testis-specific protein IZUMO1 and its receptor JUNO on the oocyte surface are essential for sperm-oocyte recognition, binding, and membrane fusion. However, these factors alone are insufficient to accomplish cytoplasmic membrane fusion. It is believed that other gametic proteins interact with them to facilitate sperm-oocyte interaction on the head and mid-tail of rat spermatozoa as well as on the surface of oocytes. In this study, Copper Transport Protein 2 (CTR2) has been identified on the head and mid-tail of rat spermatozoa as well as on the surface of oocytes. CTR2 directly interacts with both IZUMO1 and JUNO, colocalizing with IZUMO1 on the sperm head and with JUNO on the oocyte membrane. Treatment of the capacitated sperm and zona pellucida-free oocytes with anti-CTR2 antibody resulted in a significant decrease in fertilization rates in IVF experiments. These findings suggest that CTR2 plays an important role in mammalian fertilization by interacting with IZUMO1 and JUNO, providing new insights into the molecular mechanisms of mammalian sperm-oocyte adhesion and fusion.
    Keywords:  CTR2; IZUMO1; JUNO; Protein-protein interaction; Sperm-egg fusion
    DOI:  https://doi.org/10.1016/j.theriogenology.2024.10.016
  12. Front Endocrinol (Lausanne). 2024 ;15 1322592
    Evidence of apoptosis as an early event leading to cyclophosphamide-induced primordial follicle depletion in a prepubertal mouse model.
    Xia Hao, Arturo Reyes Palomares, Amandine Anastácio, Kui Liu, Kenny A Rodriguez-Wallberg.
       Introduction: The mechanisms leading to ovarian primordial follicle depletion following gonadotoxic chemotherapy with cyclophosphamide and other cytotoxic drugs are currently understood through two main explanatory theories: apoptosis and over-activation. Discrepancies between the findings of different studies investigating these mechanisms do not allow to reach a firm conclusion. The heterogeneity of cell types in ovaries and their different degrees of sensitivity to damage, cell-cell interactions, periodical follicle profile differences, model age-dependent differences, and differences of exposure durations of tested drugs may partially explain the discrepancies among studies.
    Methods: This study used intact prepubertal mice ovaries in culture as study model, in which most follicles are primordial follicles. Histological and transcriptional analyses of ovaries exposed to the active metabolite of cyclophosphamide 4-hydroperoxycyclophosphamide (4-HC) were carried out via a time-course experiment at 8, 24, 48, and 72 h.
    Results: 4-HC treated ovaries showed a significant decrease in primordial follicle density at 24 h, along with active DNA damage (TUNEL) and overexpressed apoptosis signals (cleaved-poly ADP ribose polymerase in immunohistochemistry and western blotting). Meanwhile 4-HC treatment significantly up-regulated H2ax, Casp 6, Casp 8, Noxa, and Bax in ovaries, and up-regulated Puma in primordial follicles (FISH).
    Discussion: Our results indicated that cyclophosphamide-induced acute ovarian primordial follicle depletion was mainly related to apoptotic pathways. No evidence of follicle activation was found, neither through changes in the expression of related genes to follicle activation nor in the density of growing follicles. Further validation at protein level in 4-HC-treated prepubertal mice ovaries at 24 h confirmed these observations.
    Keywords:  apoptosis; cyclophosphamide; gene expression; growing follicle; ovary; overactivation; primordial follicle; timepoint
    DOI:  https://doi.org/10.3389/fendo.2024.1322592
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