Biology subjects

Plachta, N.

Publications and source records attributed to Plachta, N..

6 recordsLinked to original sources

bioRxiv2026

Proprotein convertase activity regulates cumulus-oocyte-complex matrix integrity and cumulus cell migration during ovulation via a GDF9-dependent mechanism

Cumulus cells have well-established roles early in ovulation but the key molecules that drive their behavior in later stages, leading to follicle rupture, remain underexplored. Here, we observed that inhibition of proprotein convertases (PCSKs) via a pan-inhibitor (PCI) impaired follicular rupture and disrupted the cumulus matrix integrity within intact follicles. Reduced cumulus cell adherence to the cumulus-oocyte-complex (COC) matrix was also observed in isolated COCs and notably occurred late during the maturation window without affecting oocyte maturation. Visualization of PCSK transcript and protein expression, as well as selective inhibition of specific PCSKs, determined that the observed phenotype in COCs is likely attributed to PCSK5A inhibition. We conducted bulk RNA-sequencing and proteomics of PCI-treated COCs which revealed that PCSK inhibition caused dysregulation of extracellular matrix organization, cell migration/adhesion, and TGF-{beta} signaling pathways. Subsequent validation showed that this inhibition translated to disrupted matrix organization and altered migratory and adhesive behaviors in cumulus cells. The TGF-{beta} ligand GDF9 has a predicted PCSK cleavage site, and supplementation with GDF9 rescued matrix integrity suggesting its role as a downstream substrate of PCSKs to regulate matrix organization. Altogether, this study identified PCSK5A and GDF9 as key regulators of COC matrix integrity and cumulus cell migration during late ovulation. These findings highlight novel factors required for follicle rupture which can be leveraged for the development of fertility therapeutics and contraceptives.

cell biology↗

bioRxiv2026

Ultra-low oxygen tension during in vitro fertilization improves embryonic and adult outcomes in mice

Embryo culture, a required step during in vitro fertilization (IVF), exposes developing embryos to altered environmental conditions not normally experienced in vivo, including altered oxygen (O2) tension. Importantly, O2 influences gene expression, metabolism, and the activity of enzymes that sculpt the epigenetic landscape. The lowest O2 tension currently used in clinics during embryo culture is 5%, despite evidence that sections of the mammalian female reproductive tract have O2 levels as low at 2%. Lower O2 may therefore better mimic the in vivo environment and thus lead to improved pre- and postnatal outcomes in IVF-conceived offspring. Using our validated IVF mouse model, we show embryo culture at 2% O2 compared to culture under 5% O2 significantly improves embryo cell number, the chromatin landscape in preimplantation embryos, fetal and placental development during gestation, and metabolic function in adulthood. We further uncover mechanisms by which culture under ultra-low O2 mediates these improvements. Overall, these results suggest embryo culture with 2% O2 ameliorates adverse outcomes after IVF and provide evidence that IVF could be further improved by adjusting culture conditions to model the in vivo environment.

developmental biology↗

bioRxiv2026

Modeling human embryo adhesion using a microfluidic platform

Embryo adhesion represents the first step of implantation, yet understanding this process has been hindered by the lack of human in vitro platforms that replicate endometrial physiology. Here, we present a dual-channel microfluidic platform containing organoid-derived endometrial epithelium and primary stromal cells. Our model recapitulates important endometrial hallmarks including epithelial polarization, stromal decidualization, extracellular vesicle release, and hormone-induced receptivity. We tested its function by introducing mouse and human blastocysts and showed that embryos displayed features of initial adhesion. These included establishment of embryo-epithelial contacts initiated via the polar trophectoderm, inner cell mass repositioning, and lineage segregation. Moreover, human embryos secreted {beta}hCG indicating a functional trophoblast. Thus, this work provides a platform to study key features of embryo adhesion and endometrial receptivity, and disorders affecting embryo-endometrium interactions. TeaserEndometrium-on-a-chip shows detailed human embryo adhesion dynamics.

molecular biology↗

bioRxiv2024

Heterochromatin protein ERH represses alternative cell fates during early mammalian differentiation

Enhancer of Rudimentary Homolog (ERH) is an evolutionarily conserved protein originally characterized as promoting fission yeast heterochromatin1 and recently shown to maintain H3K9me3 heterochromatin in human fibroblasts2. Here, we find that ERH depletion in fibroblasts reverts the somatic cell H3K9me3 landscape of broad megabase size domains to an embryonic stem cell (ESC) state composed of mainly H3K9me3 peaks and enables activation of naive and pluripotency genes and transposable elements during induced pluripotent stem cell (iPSC) reprogramming. Concordantly, we find that ERH represses totipotent and alternative lineage programs during mouse preimplantation development and is required for proper segregation of the inner cell mass and trophectoderm cell lineages. During human ESC differentiation into germ layer lineages, ERH silences naive and pluripotency genes, transposable elements, and alternative lineage somatic genes. As in fission yeast, we find that mammalian ERH interacts with RNA-binding proteins to engage and repress its chromatin targets. Our findings reveal a conserved, fundamental role for ERH in cell fate specification via the initiation and maintenance of early developmental gene repression.

developmental biology↗

bioRxiv2020

The embryonic node functions as an instructive stem cell niche

In warm-blooded vertebrate embryos (mammals and birds), the body forms from a growth zone at the tail end. Hensens node, a region which induces and patterns the neural axis is located within this growth zone. The node also contains the precursors of neural, mesodermal and endodermal structures along the midline and has been suggested to contain a small population of resident stem cells. However, it is unknown whether the rest of the node constitutes an instructive stem cell niche, specifying stem cell behaviour. Here we combine transplantation of a single cell in vivo with single-cell mRNA sequencing in the chick and show that when made to enter the node, non-node-progenitor cells become resident and gain stem cell behaviour. These cells preferentially express G2/M phase cell-cycle related genes and are concentrated in posterior sub-regions of the node. The posterior part of the node therefore behaves as an instructive stem cell niche. These results demonstrate a new function for the vertebrate node during development.

developmental biology↗

bioRxiv2020

Cooperation-based sperm clusters mediate sperm oviduct entry and fertilization

Sperm cooperation has been observed in multiple species, yet its existence and benefit for reproductive success in mammals remains underexplored. Here, combining tissue-clearing with deep three-dimensional imaging, we demonstrate that postcopulatory mouse sperm congregate into unidirectional sperm cooperative clusters at the utero-tubal junction (UTJ), a key physical barrier for passage into the oviduct. Reducing sperm number in male mice by unilateral vasoligation or busulfan-treatment impairs sperm cluster formation and oviduct entry. Interestingly, sperm derived from Tex101-/- mouse has normal number, motility and morphology, yet they cannot form sperm cluster and fail to pass through the UTJ, which is at least in part due to the altered tail beating pattern of the Tex101-/- sperm. Moreover, Tex101-/- sperms defect in oviduct entry cannot be rescued by the presence of wild-type (WT) sperm in the same uteri by sequential mating, suggesting sperm cooperative cluster as an essential behavior contributing to male fertility, which could be related to human infertility or subfertility.

developmental biology↗