Biology subjects

Drexler, H. C. A.

Publications and source records attributed to Drexler, H. C. A..

6 recordsLinked to original sources

bioRxiv2026

Fertilization offsets the maternal age effect on mouse oocytes provided the oviduct is not itself aged

Advanced maternal age compromises oocyte quality, and it is widely assumed that these deficits are transmitted to embryos. However, because most studies rely on in vivo conception, it has been difficult to separate the effects of oocyte aging from those of an aged fertilization environment. In aging mice, we observed that the fraction of ovulated oocytes forming implantation sites after in vivo conception fell ~3.7-fold, raising the question of whether this was due to reduced fertilization, reduced embryo quality or reduced support from the aged reproductive tract. Therefore we fertilized oocytes of aged and young mice in vitro with a shared young-donor sperm preparation, holding the fertilization environment constant and removing paternal variability. Hallmarks of maternal age were largely offset following fertilization in vitro: aged oocytes produced blastocysts at rates comparable to young controls, with altered - but not deficient - cell-lineage composition and no detectable impairment in development to term (E18.5) after transfer to young oviducts. Proteomic analysis revealed that, unlike the transcriptomic signature, the proteomic age signature of oocytes was not faithfully propagated to the blastocyst: for a subset of proteins, particularly those depleted in aged oocytes, the direction of the age effect reversed between oocyte and blastocyst. Comparison with parthenogenetically activated oocytes showed this divergence to be fertilization-dependent, implicating fertilization - rather than mere embryonic cleavage - as the driver of proteomic change. Stable-isotope labelling in live embryos showed that blastocysts from aged, fertilized oocytes both synthesized more new protein and retained less maternal protein than young counterparts; neither effect was detectable after parthenogenesis. Puromycin labelling, by contrast, showed a maternal-age-associated rise in bulk synthesis regardless of route. Together, these results indicate that the maternal-age effect on the oocyte proteome is labile rather than fixed and can be offset by fertilization itself, provided the maternal environment is not itself aged.

developmental biology↗

bioRxiv2025

A novel and critical role of the intracellular Zona Pellucida protein 2 (ZP2) for blastocyst formation in mice

The zona pellucida (ZP) is the quintessential extracellular structure of mammalian oocytes. Contrary to long-standing view that the synthesis of ZP proteins is specific to oocytes and muted in embryos, we report here that the major zona pellucida protein ZP2 is re-synthesized and functionally required during mouse embryo development. The orthogonal methods of mass spectrometry and monoclonal immunofluorescence revealed an increase of ZP2 abundance at the 8-cell / morula stage, which did not occur when zygotes were microinjected with translation-blocking oligonucleotides (morpholinos). To shed light on the functional significance of embryonic ZP2, we performed protein knockdown using immunodepletion (by Trim-Away) while at the same time preventing replenishment (by translation-blocking morpholino). ZP2 knockdown resulted in morula stage retardation and formation of defective blastocysts, whose cell lineages trophectoderm and primitive endoderm were smaller and less able to support post-implantation development. The transcriptional correlates of these morphological alterations had a gene ontology (biological process) signature that included cell lineage-relevant terms ( endoderm development, gastrulation), while the proteomic correlates had a gene ontology signature related to protein synthesis. Taken together, these results call into question the traditional model that ZP proteins function solely in the extracellular space and accompany embryogenesis as passive bystanders: on the contrary, ZP proteins also participate actively in the intracellular processes of early embryogenesis.

developmental biology↗

bioRxiv2024

Sphingolipid metabolism orchestrates the establishment of the adult hair follicle stem cell niche to control skin homeostasis

Bioactive sphingolipids serve as an essential building block of membranes, forming a selective barrier that ensures subcellular compartmentalization and facilitates cell type-specific intercellular communication through regulation of the plasma membrane receptor repertoire. How cell type-specific lipid compositions are achieved and what is their functional significance in tissue morphogenesis and maintenance has remained unclear. Here, we identify a stem-cell specific role for ceramide synthase 4 (CerS4) in orchestrating fate decisions in skin epidermis. Deletion of CerS4 in the epidermis prevents the effective development of the adult hair follicle bulge stem cell (HFSCs) niche due to altered differentiation trajectories of HFSC precursors towards upper hair follicle and inner bulge fates. Mechanistically, HFSC differentiation defects arise from an imbalance of key ceramides and their derivate sphingolipids in HFSCs associated with hyperactivity of canonical Wnt signaling. Impaired HFSC niche establishment leads to disruption of hair follicle architecture and hair follicle barrier function, ultimately triggering a T helper cell 2 - dominated immune infiltration closely resembling human atopic dermatitis. This work uncovers a fundamental role for a cell state-specific sphingolipid profile in epidermal stem cell homeostasis and the role of an intact stem cell niche in maintaining an intact skin barrier.

developmental biology↗

bioRxiv2022

Intracellular fraction of zona pellucida protein 3 is required for the oocyte to embryo transition in mice

In oocyte biology the zona pellucida has long been known to operate three extracellular functions, namely, encasing the oocytes in ovarian follicles, mediating sperm-oocyte interaction and preventing premature embryo contact with maternal epithelia. The present study uncovers a fourth function that is fundamentally distinct from the other three, being critical for embryonic cell survival. Intriguingly, the three proteins of the mouse zona pellucida (ZP1, ZP2, ZP3) were found abundantly present also inside the embryo four days after fertilization, as shown by mass spectrometry, immunoblotting and immunofluorescence. Trim-away-mediated knockdown of ZPs in fertilized oocytes resulted in various grades of embryopathy: knockdown of ZP1 impeded blastocyst expansion, knockdown of ZP2 hampered the 2nd zygotic cleavage, while knockdown of ZP3 hampered the 1st zygotic cleavage - unlike the overexpression. Transcriptome analysis of ZP3-knockdown embryos pointed at defects of cytoplasmic translation in the context of embryonic genome activation. This conclusion was supported by reduced protein synthesis in the ZP3-knockdown and by the lack of cleavage arrest when knockdown was postponed from the 1-cell to the late 2-cell stage. These data place constraints on the long-standing notion that the zona pellucida proteins only operate in the extracellular space. We postulate that such noncanonical localization of ZP3 reflect novel roles in the embryos interior during the oocyte-to-embryo transition in mice. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/521410v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@18c0ca2org.highwire.dtl.DTLVardef@19168aeorg.highwire.dtl.DTLVardef@16f784forg.highwire.dtl.DTLVardef@143c4b7_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2018

An integrated genome-wide multi-omics analysis of gene expression dynamics in the preimplantation mouse embryo

Early mouse embryos have an atypical translational machinery comprised of cytoplasmic lattices, poorly competent for translation. Thus, the impact of transcriptomic changes on the operational levels of proteins has likely been overestimated in the past. To find out, we used liquid chromatography-tandem mass spectrometry to detect and quantify 6,550 proteins in the oocyte and in six developmental stages (from zygote to blastocyst) collected in triplicates, and we also performed mRNA sequencing.\n\nIn contrast to the known split between the 2-cell and 4-cell stages at the transcript level, on the protein level the oocyte-to-embryo transition appeared to last until the morula stage. In general, protein abundance profiles were weakly correlated with those of their cognate mRNAs and we found little or no concordance between changes in protein and transcript expression relative to the oocyte at early stages. However, concordance increased towards morula and blastocyst, hinting at a more direct coupling of proteins with transcripts at these stages, in agreement with the increase in free ribosome abundance. Independent validation by immunofluorescence and qPCR confirmed the existence of genes featuring strongly positively and negatively correlated protein and transcript. Moreover, consistent coverage of most known protein complexes indicates that our dataset represents a large fraction of the expressed proteome. Finally, we identified 20 markers, including members of the endoplasmic reticulum pathway, for discriminating between early and late stages.\n\nThis resource contributes towards closing the gap between the predicted phenotype, based on mRNA, and the actual phenotype, based on protein, of the mouse embryo.

developmental biology↗

bioRxiv2017

Attomol-level quantification of chemically modified ribonucleosides enabled by capillary porous graphitic carbon columns in nano LC-MS

Post-transcriptional chemical modifications of (t)RNA molecules are crucial in fundamental biological processes, such as translation. Despite their biological importance and accumulating evidence linking them to various human diseases, technical challenges have limited the development of methods for reliable detection and accurate quantification of these modifications. Here, we present a sensitive capillary nanoflow liquid chromatography mass spectrometry (nLC-MS) pipeline for quantitative high-resolution analysis of ribonucleoside modifications from complex biological samples. We evaluated two porous graphitic carbon (PGC) materials as stationary phases for reversed-phase separation of ribonucleosides and found that both PGC matrices have excellent retention and separation characteristics, as well as the capability to separate structural isomers. Using PGC matrices in nLC-MS yielded excellent signal-to-noise ratios in a detection range spanning up to six orders of magnitude, allowing for the analysis of individual ribonucleosides down to attomol concentrations. Furthermore, normalizing the obtained signal intensities to a stable isotope labeled spike-in enabled direct comparison of ribonucleoside levels between different samples. In conclusion, capillary PGC columns coupled to nLC-MS constitute a powerful and sensitive tool for quantitative analysis of chemically modified ribonucleosides in complex biological samples. This setup will be invaluable for further unraveling the intriguing and multifaceted biological roles of RNA modifications.

biochemistry↗