Bioengineering embryo models
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Melatonin affects trophoblast epithelial-to-mesenchymal transition and oxidative damage resistance by modulating GDF15 expression to promote embryo implantation
Melatonin is widely observed in the female reproductive system and regulates trophoblast cell functions, but its effects on embryo implantation and underlying mechanisms are not well understood. By constructing an in vitro embryo culture model, we found that melatonin enhances migration and implantation in human and mouse trophoblast cells. It also significantly promoted HTR-8/SVneo cell proliferation, inhibited apoptosis, enhanced migration, and mitigated oxidative damage. Further investigation revealed that melatonin promoted trophoblast cell migration and increased the in vitro implantation rate of HTR-8/SVneo spheroids by promotes epithelial-mesenchymal transition (EMT) via the growth differentiation factor 15 (GDF15)–mothers against decapentaplegic homolog 2/3 (SMAD2/3) pathway. Additionally, melatonin increased the levels of glutathione peroxidase 4 (GPX4) and glutathione (GSH) in HTR-8/SVneo cells by upregulating the expression of GDF15, inhibiting reactive oxygen species (ROS) accumulation, and increasing mitochondrial membrane potential, thus suppressing apoptosis during oxidative stress. In conclusion, melatonin promotes EMT in trophoblast cells via GDF15-SMAD2/3 pathway and partially induces the expression of GPX4 through GDF15 to enhance oxidative damage resistance in trophoblast cells. These findings highlight melatonin’s regulatory role in embryo implantation and suggest new avenues for exploring its biological effects in reproduction and clinical applications.
MADS31 supports female germline development by repressing the post-fertilization programme in cereal ovules
The female germline of flowering plants develops within a niche of sporophytic (somatic) ovule cells, also referred to as the nucellus. How niche cells maintain their own somatic developmental programme, yet support the development of adjoining germline cells, remains largely unknown. Here we report that MADS31, a conserved MADS-box transcription factor from the B-sister subclass, is a potent regulator of niche cell identity. In barley, MADS31 is preferentially expressed in nucellar cells directly adjoining the germline, and loss-of-function mads31 mutants exhibit deformed and disorganized nucellar cells, leading to impaired germline development and partial female sterility. Remarkably similar phenotypes are observed in mads31 mutants in wheat, suggesting functional conservation within the Triticeae tribe. Molecular assays indicate that MADS31 encodes a potent transcriptional repressor, targeting genes in the ovule that are normally active in the seed. One prominent target of MADS31 is NRPD4b, a seed-expressed component of RNA polymerase IV/V that is involved in epigenetic regulation. NRPD4b is directly repressed by MADS31 in vivo and is derepressed in mads31 ovules, while overexpression of NRPD4b recapitulates the mads31 ovule phenotype. Thus, repression of NRPD4b by MADS31 is required to maintain ovule niche functionality. Our findings reveal a new mechanism by which somatic ovule tissues maintain their identity and support germline development before transitioning to the post-fertilization programme.
Coupling of cell shape, matrix and tissue dynamics ensures embryonic patterning robustness
Tissue patterning coordinates morphogenesis, cell dynamics and fate specification. Understanding how precision in patterning is robustly achieved despite inherent developmental variability during mammalian embryogenesis remains a challenge. Here, based on cell dynamics quantification and simulation, we show how salt-and-pepper epiblast and primitive endoderm (PrE) cells pattern the inner cell mass of mouse blastocysts. Coupling cell fate and dynamics, PrE cells form apical polarity-dependent actin protrusions required for RAC1-dependent migration towards the surface of the fluid cavity, where PrE cells are trapped due to decreased tension. Concomitantly, PrE cells deposit an extracellular matrix gradient, presumably breaking the tissue-level symmetry and collectively guiding their own migration. Tissue size perturbations of mouse embryos and their comparison with monkey and human blastocysts further demonstrate that the fixed proportion of PrE/epiblast cells is optimal with respect to embryo size and tissue geometry and, despite variability, ensures patterning robustness during early mammalian development.
Direct specification of lymphatic endothelium from mesenchymal progenitors
During embryogenesis, endothelial cells (ECs) are generally described to arise from a common pool of progenitors termed angioblasts, which diversify through iterative steps of differentiation to form functionally distinct subtypes of ECs. A key example is the formation of lymphatic ECs (LECs), which are thought to arise largely through transdifferentiation from venous endothelium. Opposing this model, here we show that the initial expansion of mammalian LECs is primarily driven by the in situ differentiation of mesenchymal progenitors and does not require transition through an intermediate venous state. Single-cell genomics and lineage-tracing experiments revealed a population of paraxial mesoderm-derived Etv2+Prox1+ progenitors that directly give rise to LECs. Morphometric analyses of early LEC proliferation and migration, and mutants that disrupt lymphatic development supported these findings. Collectively, this work establishes a cellular blueprint for LEC specification and indicates that discrete pools of mesenchymal progenitors can give rise to specialized subtypes of ECs.
Translocation-specific polymerase chain reaction in preimplantation genetic testing for recurrent translocation carrier
It is occasionally necessary to distinguish balanced reciprocal translocations from normal diploidy since balanced carriers can have reproductive problems or manifest other disease phenotypes. It is challenging to do this however using next generation sequencing (NGS) or microarray-based preimplantation genetic testing (PGT). In this study, discarded embryos were harvested from balanced reciprocal translocation carriers intending PGT that were determined to be unsuitable for transfer due to unbalanced translocations or translocation-unrelated aneuploidy. Two trophoectoderm biopsy samples were obtained from each single embryo. Whole genome amplification (WGA) was performed either by looping-based amplification (LBA) or multiple displacement amplification (MDA). NGS-based copy number variation (CNV) analysis as well as translocation-specific PCR was performed for each. We used embryo samples from t(8;22)(q24.13;q11.2) and t(11;22)(q23;q11.2) carriers since they are recurrent constitutional translocations that have nearly identical breakpoints even among independent unrelated families. CNV analysis was generally consistent between the two WGA methods. Translocation-specific PCR allowed us to detect each derivative chromosome in the MDA WGA samples but not with the LBA method, presumably due to coverage bias or the shorter sized WGA products. We successfully distinguished balanced reciprocal translocations from normal diploidy in normal samples with CNV analysis. A combination of CNV analysis and translocation-specific PCR using MDA-amplified WGA product can distinguish between balanced reciprocal translocation and normal diploidy in preimplantation genetic testing for structural rearrangements (PGT-SR).
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