bims-mazytr 2025-05-18 papers

Issue of 2025–05–18
seven papers selected by
川一刀

Birth Defects Res. 2025 May;117(5): e2484

Blastocyst Cavity Expansion Promotes Cell Polarization During Early Development of Mouse Embryos.

Zheng Guo, Xinxin Lv, Jianwen Li, Shiping Yue, Jing Du.

BACKGROUND: Cell polarization is an important morphological process that is crucial for the formation and function of tissues and organs. The blastocyst cavity expansion is an apparent event during the second cell fate specification in mouse embryos, yet its impact on cell polarization remains unclear. In this study, we investigate the effects of blastocyst cavity expansion on cell polarization.
METHODS: The methods of this study involve hyperosmotic treatment or disruption of TE cortical tension by laser ablation, combined with immunofluorescence.
RESULTS: We found that inhibition of the blastocyst cavity expansion through hypertonic treatment or disruption of TE cortical tension by laser ablation suppresses the levels of the ζ isotype of protein kinase C (PKC ζ) which is a member of the atypical PKC subfamily involved in cell polarization. We further found that during the embryonic stages E3.5 to E4.0, the expression of extracellular signal-regulated kinase 1 (ERK1), a key upstream regulator of PKC ζ, is altered in a similar tendency to that of PKC ζ, indicating a potential regulatory function of ERK1 in cell polarization during early development of mouse embryos.
CONCLUSIONS: This study reveals the function of the mechanical behavior of embryos in cell polarization of early mammalian embryos. The relationship between cell polarization and blastocyst cavity expansion in early embryonic development provides a new understanding, thereby offering fresh insights for the screening and detection of indicators for normal blastocyst development.

Keywords: PKC ζ; blastocyst cavity; cell polarization; early mammalian embryos; mouse embryos

DOI: https://doi.org/10.1002/bdr2.2484

Int J Mol Sci. 2025 Apr 25. pii: 4098. [Epub ahead of print]26(9):

The Importance of Mitochondrial Processes in the Maturation and Acquisition of Competences of Oocytes and Embryo Culture.

Elżbieta Gałęska, Alicja Kowalczyk, Marcjanna Wrzecińska, Mercedes Camiña García, Ewa Czerniawska-Piątkowska, Szymon Gwoździewicz, Wojciech Witkiewicz, Zbigniew Dobrzański.

Mitochondria, as multifunctional and partially independent structures, play a crucial role in determining essential life processes. Recently, their significance in reproductive biology has gained increasing attention. This review aims to comprehensively analyse the role of mitochondrial processes in oocyte maturation and embryo culture. A comprehensive literature review was conducted to highlight the importance of mitochondrial activity in the early stages of life formation. Proper mitochondrial function provides energy, maintains genomic stability, and ensures optimal conditions for fertilisation and embryo progression. Understanding these processes is essential to optimise culture conditions and identify new mitochondrial biomarkers that improve reproductive success and improve assisted reproductive technologies (ARTs). Enhancing mitochondrial function in female reproductive cells is the key to improving oocyte and embryo quality, which can lead to better in vitro fertilisation and embryo transfer. Furthermore, advances in diagnostic techniques, such as mitochondrial genome sequencing, offer a more precise understanding of the relationship between mitochondrial health and oocyte quality. However, fully understanding mitochondrial functions is only part of the challenge. Expanding knowledge of the interactions between mitochondria and other cellular structures is crucial for future advancements in reproductive medicine. Understanding these complex relationships will provide deeper insight into improving reproductive outcomes and embryo development.

Keywords: embryo culture; maturation; mitochondria; oocytes; reproduction

DOI: https://doi.org/10.3390/ijms26094098

Nature. 2025 May 14.

Divergent DNA methylation dynamics in marsupial and eutherian embryos.

Bryony J Leeke, Wazeer Varsally, Sugako Ogushi, Jasmin Zohren, Sergio Menchero, Aurélien Courtois, Daniel M Snell, Aurélie Teissandier, Obah Ojarikre, Shantha K Mahadevaiah, Fanny Decarpentrie, Rebecca J Oakey, John L VandeBerg, James M A Turner.

Based on seminal work in placental species (eutherians)1-10, a paradigm of mammalian development has emerged wherein the genome-wide erasure of parental DNA methylation is required for embryogenesis. Whether such DNA methylation reprogramming is, in fact, conserved in other mammals is unknown. Here, to resolve this point, we generated base-resolution DNA methylation maps in gametes, embryos and adult tissues of a marsupial, the opossum Monodelphis domestica, revealing variations from the eutherian-derived model. The difference in DNA methylation level between oocytes and sperm is less pronounced than that in eutherians. Furthermore, unlike the genome of eutherians, that of the opossum remains hypermethylated during the cleavage stages. In the blastocyst, DNA demethylation is transient and modest in the epiblast. However, it is sustained in the trophectoderm, suggesting an evolutionarily conserved function for DNA hypomethylation in the mammalian placenta. Furthermore, unlike that in eutherians, the inactive X chromosome becomes globally DNA hypomethylated during embryogenesis. We identify gamete differentially methylated regions that exhibit distinct fates in the embryo, with some transient, and others retained and that represent candidate imprinted loci. We also reveal a possible mechanism for imprinted X inactivation, through maternal DNA methylation of the Xist-like noncoding RNA RSX11. We conclude that the evolutionarily divergent eutherians and marsupials use DNA demethylation differently during embryogenesis.

DOI: https://doi.org/10.1038/s41586-025-08992-2

STAR Protoc. 2025 May 08. pii: S2666-1667(25)00178-9. [Epub ahead of print]6(2): 103772

Protocol to assess the impact of sperm RNA on mouse preimplantation embryos using microinjection.

Grace S Lee, Natalie A Trigg, Colin C Conine.

Zygotic microinjections show that sperm RNAs transmit non-genetically inherited phenotypes to offspring and influence embryonic development. Here, we present a protocol for the micromanipulation of mouse zygotes to introduce physiologically relevant levels of sperm RNA. We describe steps for producing functional mRNAs in vitro; purifying mouse sperm RNAs; and preparing, microinjecting, and culturing zygotes. This protocol facilitates causal analysis between sperm RNA and gene regulation postfertilization. For complete details on the use and execution of this protocol, please refer to Trigg et al.1.

Keywords: Biotechnology and bioengineering; Developmental biology; Gene Expression

DOI: https://doi.org/10.1016/j.xpro.2025.103772

Curr Protoc. 2025 May;5(5): e70145

Visualization of the Cytoskeleton in Fixed Drosophila Embryos.

Junnan Fang, Jovan S Brockett, Weiyi Tian, Yuqing Hua, Elizabeth R Gavis, Dorothy A Lerit.

Embryogenesis necessitates the precise orchestration of cellular events to establish tissue patterning, developmental robustness, and viability. Syncytial embryogenesis, as in Drosophila melanogaster, poses added challenges as the synchronous and rapid nuclear divisions prior to cellularization occur within a shared cytoplasm. While the first several rounds of nuclear divisions occur within the center of the embryo, the nuclei progressively migrate peripherally, giving rise to the syncytial blastoderm. This spatial choreography hinges upon the dynamic interplay of actin and microtubules. Actin and microtubules coordinate nuclear division and position while preventing deleterious nuclear collisions. Additionally, the cytoskeleton also facilitates the segregation of organelles and molecular cargoes, including cell fate determinants required for cellular differentiation. As development progresses, actin and microtubules drive cellularization events for both germline and somatic cell lineages. Cytoskeletal disruption causes developmental arrest and embryonic lethality, underscoring its importance for embryogenesis. Given the significance of the cytoskeleton to these events, its visualization remains a cornerstone of cell and developmental biology research. Indeed, studies of the Drosophila embryo cytoskeleton have yielded valuable insights into cell biological mechanisms and developmental pathways conserved in various systems. Nevertheless, achieving optimal preservation of filamentous cytoskeletal structures poses technical challenges. Here, we present an embryo fixation method tailored to enhance the visualization of actin and microtubules via standard light microscopy approaches. This protocol complements immunofluorescence and molecular labeling techniques, including the direct labeling of fluorescently tagged proteins or mRNAs. By enabling detailed analysis of the cytoskeleton, this method expands opportunities to investigate the molecular mechanisms underlying embryo development and related processes. © 2025 Wiley Periodicals LLC. Basic Protocol 1: Preparation of embryos for immunofluorescence of actin or microtubules Basic Protocol 2: Coupling immunofluorescence of the cytoskeleton with visualization of mRNAs via smFISH.

Keywords: RNA localization; actin; cytoskeleton; imaging; microtubules

DOI: https://doi.org/10.1002/cpz1.70145

Adv Sci (Weinh). 2025 May 11. e2504066

Intermediate Filament Protein BFSP1 Maintains Oocyte Asymmetric Division by Modulating Spindle Length.

Yu Li, Hanwen Zhang, Wenjun Zeng, Yilong Miao, Shaochen Sun, Yu Zhang, Bo Xiong.

The cytoskeleton is composed of microtubules, microfilaments, and intermediate filaments in cells. While the functions of microtubules and microfilaments have been well elucidated, the roles of intermediate filaments and associated proteins remain largely unknown, especially in meiosis. BFSP1 is an intermediate filament protein mainly expressed in the eye lens to play important roles in the development of congenital cataract. Here, we document that BFSP1 functions as a spindle regulator to drive the oocyte asymmetric division. Specifically, we found that BFSP1 distributed on the spindle apparatus during oocyte meiotic maturation. Depletion of BFSP1 resulted in symmetric division of oocytes, accompanied by the formation of elongated spindles at metaphase I and anaphase/telophase I stages. In addition, immunoprecipitation combined with mass spectrometry analysis identified MAP1B, a microtubule-associated protein, as an interacting partner of BFSP1. Depletion or mutation of MAP1B phenocopied the meiotic defects observed in BFSP1-depleted oocytes, and expression of exogenous MAP1B-EGFP in BFSP1-depleted oocytes recovered the spindle length and asymmetric division. We further determined that BFSP1 recruited molecular chaperone HSP90α on the spindle to stabilize MAP1B, thereby controlling the spindle length. To sum up, our findings reveal a unique meiotic role for BFSP1 in the regulation of spindle dynamics and oocyte asymmetric division.

Keywords: BFSP1; asymmetric division; intermediate filament protein; oocyte meiosis; spindle length

DOI: https://doi.org/10.1002/advs.202504066

Nature. 2025 May 14.

Marsupial embryos lack the epigenetic reset seen in placental mammals.

Keywords: Developmental biology; Epigenetics

DOI: https://doi.org/10.1038/d41586-025-01477-2