Biology subjects

Rosenwaks, Z.

Publications and source records attributed to Rosenwaks, Z..

8 recordsLinked to original sources

bioRxiv2026

Modeling human embryonic adrenogenesis in pluripotentstem cell-derived corticomedullar-like assembloids

During embryogenesis, the cortical and medullary compartments of the adrenal gland emerge from two distinct sources: intermediate mesoderm-derived steroidogenic progenitors that comprise the cortex, and migratory neural crest-derived catecholaminergic progenitors that give rise to the medulla. The distinct cellular origins and paracrine signaling environments that foster induction, differentiation, and/or migration of cortical and medullary layers present challenges to recapitulating their co-emergence and incorporation in a human pluripotent stem cell (hPSC) based system. To address this, we developed an approach for modeling the adreno-gonadal primordium (AGP) in compound organoids that are organized along a gradient of NR5A1 expression and which unexpectedly incorporate SOX10-expressing Schwann cell precursors that ultimately generate chromaffin cells. Deconstruction of paracrine signaling within AGP-like organoids (AGPLOs) identified a fibroblast growth factor 9 (FGF9)-driven mechanism that expands bridge cell-like chromaffin progenitors and correlates to paracrine signaling cues encountered by physiological correlates along their migration corridor to the cortex in vivo. Combination of NR5A1-expressing cells with chromaffin cell clusters generated corticomedullar-like assembloids (CMLAs) that generated steroids and catecholamines and were responsive to adrenocorticotropic hormone. This work establishes a platform for modeling the reciprocal signaling relationships that drive adrenal gland development and function in health and disease and provides an approach for generating hPSC-derived adrenal cells/tissues that can be applied therapeutically.

developmental biology↗

bioRxiv2025

Dysregulation of the actin cytoskeleton and FMRP causes polar body protrusion defects in human fragile X premutation and aged oocytes

Women carrying the fragile X premutation (55-200 CGG repeat expansion, PM) are at risk for developing fragile X-associated primary ovarian insufficiency (FXPOI), which is preceded by fragile X-associated diminished ovarian reserve (FXDOR). So far, the cause of FXDOR/FXPOI could not be comprehensively examined due to the scarcity of human ovarian tissue and oocytes. From studies in model systems, it was proposed that molecular abnormalities within the ovaries or a diminished primordial follicle pool cause FXDOR/FXPOI. To elucidate the defects instigating FXDOR/FXPOI, we examined human oocytes obtained from PM carriers undergoing in vitro fertilization (IVF). We found that the number of MII oocytes was reduced suggesting that the maturation of the oocytes is constrained in PM carriers. Furthermore, immature PM oocytes contained abnormal inclusions, irregular ubiquitin levels and DNA breaks. Despite these defects PM oocytes passed the DNA damage checkpoints. However, in anaphase I PM oocytes failed to initiate the protrusion of the first polar body. In addition, these oocytes amassed bundle actin structures, lacked an actin cap and had elevated profilin1 level. Profilin1 limits the formation of branched actin structures which are necessary for actin cap formation and membrane protrusions. Surprisingly, our results suggest that in PM oocytes an increase in FMRP elevates the profilin1 translation, which leads to the cytoskeleton defects and deficiencies in formation of the first polar body. We also analyzed the decline of MII oocytes in aging human ovaries. Similar, we found that the profilin1 expression and formation of the actin cytoskeleton were dysregulated due to appearance of cytoplasmatic FMRP foci in aged human oocytes. Thus, these results reveal that defects during anaphase I hinder the maturation of human oocytes resulting in FXDOR/FXPOI in PM carriers and a reduction in mature oocytes in women with advanced maternal age.

cell biology↗

bioRxiv2023

Maternal H3.3-Mediated Paternal Genome Reprogramming Contributes to Minor Zygotic Genome Activation

In mice, zygotic genome activation (ZGA) is initiated at the late-one-cell stage, accompanied by an extensive incorporation of the histone variant H3.3 into the parental genomes. However, it is unclear how H3.3 engages in the onset of ZGA. Here, using the H3.3B-HA-tagged mouse model, we found that the paternal and maternal genomes are activated asynchronously. Paternally expressed H3.3 begins deposition on the zygotic genome at the early two-cell stage, whereas the deposition of maternally expressed H3.3 is delayed until the four-cell stage. Oocyte-stored maternal H3.3 (mH3.3) is crucial for cleavage development and minor ZGA. Deposition of mH3.3 on the paternal genome occurs globally during the protamine-to-histone transition but shows preferential enrichment at CpG-rich TSSs after the initial round of DNA replication. Depletion of mH3.3 can lead to a loss of H3K27ac, resulting in minor ZGA failure and early embryonic arrest. Mechanistically, mH3.3 deposition on the sperm genome removes repressive histone modifications, promotes the establishment of active histone modifications, and in turn enables the initiation of minor ZGA from the paternal genome. Our study highlights the pivotal role of mH3.3 in paternal genome reprogramming and minor ZGA initiation.

genetics↗

bioRxiv2023

Activation of the Maternal Genome Through Asymmetric Distribution of Oocyte-Genome-Associated Histone H3.3

Upon fertilization, the typically silent and epigenetically repressed oocyte genome undergoes activation, yet the precise mechanism remains unclear. The histone variant H3.3 is evenly distributed throughout the oocyte genome, suggesting its involvement in repression. This study reveals that oocyte-genome-associated H3.3 (oH3.3) undergoes asymmetric segregation among four-cell stage blastomeres, persisting in only two blastomeres through the blastocyst stage. These oH3.3-retaining blastomeres maintain a repressive state characterized by high levels of the chromatin marker H3K9me2. Intriguingly, single-cell RNA-seq analysis revealed asymmetric transcriptional activation between paternal and maternal genomes, with the maternal genome being considerably less active. We propose a model wherein oH3.3 and associated oocyte DNA co-segregate during mitosis, allowing two blastomeres to inherit oH3.3 and a strand of oocyte DNA from maternal chromatids. Meanwhile, the other blastomeres acquire newly synthesized DNA associated with the nascent histone H3, which lacks oocyte-specific repressive modifications. Consequently, full maternal genome activation occurs in two of the four-cell stage blastomeres, while the remaining two, which retain oH3.3, remain partially repressed. This study uncovers a previously unrecognized H3.3 mediated mechanism for maternal genome activation.

developmental biology↗

bioRxiv2023

Automatic Ploidy Prediction and Quality Assessment of Human Blastocyst Using Time-Lapse Imaging

Assessing fertilized human embryos is crucial for in vitro-fertilization (IVF), a task being revolutionized by artificial intelligence and deep learning. Existing models used for embryo quality assessment and chromosomal abnormality (ploidy) detection could be significantly improved by effectively utilizing time-lapse imaging to identify critical developmental time points for maximizing prediction accuracy. Addressing this, we developed and compared various embryo ploidy status prediction models across distinct embryo development stages. We present BELA (Blastocyst Evaluation Learning Algorithm), a state-of-the-art ploidy prediction model surpassing previous image- and video-based models, without necessitating subjective input from embryologists. BELA uses multitask learning to predict quality scores that are used downstream to predict ploidy status. By achieving an AUC of 0.76 for discriminating between euploidy and aneuploidy embryos on the Weill Cornell dataset, BELA matches the performance of models trained on embryologists manual scores. While not a replacement for preimplantation genetic testing for aneuploidy (PGT-A), BELA exemplifies how such models can streamline the embryo evaluation process, reducing time and effort required by embryologists.

developmental biology↗

bioRxiv2019

Human induced pluripotent stem cell-derived neuroectodermal epithelial cells mistaken for blood-brain barrier-forming endothelial cells

Brain microvascular endothelial cells (BMECs) possess unique properties underlying the blood-brain-barrier (BBB), that are crucial for homeostatic brain functions and interactions with the immune system. Modulation of BBB function is essential for treatment of neurological diseases and effective tumor targeting. Studies to-date have been hampered by the lack of physiological models using cultivated human BMECs that sustain BBB properties. Recently, differentiation of induced pluripotent stem cells (iPSCs) into cells with BBB-like properties has been reported, providing a robust in vitro model for drug screening and mechanistic understanding of neurological diseases. However, the precise identity of these iBMECs remains unclear. Employing single-cell RNA sequencing, bioinformatic analysis and immunofluorescence for several pathways, transcription factors (TFs), and surface markers, we examined the molecular and functional properties of iBMECs differentiated either in the absence or presence of retinoic acid. We found that iBMECs lack both endothelial-lineage genes and ETS TFs that are essential for the establishment and maintenance of EC identity. Moreover, iBMECs fail to respond to angiogenic stimuli and form lumenized vessels in vivo. We demonstrate that human iBMECs are not barrier-forming ECs but rather EpCAM+ neuroectodermal epithelial cells (NE-EpiCs) that form tight junctions resembling those present in BBB-forming BMECs. Finally, overexpression of ETS TFs (ETV2, FLI1, and ERG) reprograms NE-EpiCs to become more like the BBB-forming ECs. Thus, although directed differentiation of human iBMECs primarily gives rise to epithelial cells, overexpression of several ETS TFs can divert them toward a vascular BBB in vitro.

cell biology↗

bioRxiv2018

Robust Automated Assessment of Human Blastocyst Quality using Deep Learning

Morphology assessment has become the standard method for evaluation of embryo quality and selecting human blastocysts for transfer in in vitro fertilization (IVF). This process is highly subjective for some embryos and thus prone to human bias. As a result, morphological assessment results may vary extensively between embryologists and in some cases may fail to accurately predict embryo implantation and live birth potential. Here we postulated that an artificial intelligence (AI) approach trained on thousands of embryos can reliably predict embryo quality without human intervention.\n\nTo test this hypothesis, we implemented an AI approach based on deep neural networks (DNNs). Our approach called STORK accurately predicts the morphological quality of blastocysts based on raw digital images of embryos with 98% accuracy. These results indicate that a DNN can automatically and accurately grade embryos based on raw images. Using clinical data for 2,182 embryos, we then created a decision tree that integrates clinical parameters such as embryo quality and patient age to identify scenarios associated with increased or decreased pregnancy chance. This IVF data-driven analysis shows that the chance of pregnancy varies from 13.8% to 66.3%.\n\nIn conclusion, our AI-driven approach provides a novel way to assess embryo quality and uncovers new, potentially personalized strategies to select embryos with an improved likelihood of pregnancy outcome.

bioinformatics↗

bioRxiv2017

Tripolar mitosis drives the association between maternal genotypes of PLK4 and aneuploidy in human preimplantation embryos

Aneuploidy is prevalent in human preimplantation embryos and is the leading cause of pregnancy loss. Many aneuploidies arise during oogenesis, increasing in frequency with maternal age. Superimposed on these meiotic aneuploidies are a range of errors occurring during early mitotic divisions of the embryo, contributing to widespread chromosomal mosaicism. Here we reanalyzed a published dataset comprising preimplantation genetic testing for aneuploidy in 24,653 blastomere biopsies from day-3 cleavage-stage embryos, as well as 17,051 trophectoderm biopsies from day-5 blastocysts. We focused on complex abnormalities that affected multiple chromosomes simultaneously, seeking to quantify their incidences and gain insight into their mechanisms of formation. In addition to well-described patterns such as triploidy and haploidy, we identified 4.7% of day-3 blastomeres possessing karyotypes suggestive of tripolar mitosis in normally-fertilized diploid zygotes or descendant diploid cells. We further supported this hypothesis using time-lapse data from an intersecting set of 77 cleavage-stage embryos. The diploid tripolar signature was rare among day-5 blastocyst biopsies (0.5%), suggesting that complex aneuploidy generated by tripolar mitosis impairs cellular and/or early embryonic survival. Strikingly, we found that the tripolar mitosis mechanism is responsible for the previously described association with common maternal genetic variants spanning PLK4. Our findings are consistent with the role of PLK4 as the master regulator of centriole duplication with a known capacity to induce tripolar mitosis when mutated or mis-expressed. Taken together, we propose that tripolar mitosis is a key mechanism generating karyotype-wide aneuploidy in cleavage-stage embryos and implicate PLK4-mediated centrosome abnormality as a factor influencing its occurrence.

genetics↗