Biology subjects

Rosental, B.

Publications and source records attributed to Rosental, B..

10 recordsLinked to original sources

bioRxiv2026

Primordial endocrine cells uncouple sexual differentiation from sex-chromosomes

Sexuality among the animal kingdom is remarkably plastic, spanning from gonochorism to sequential or simultaneous hermaphroditism. Over 70 years ago, Charniaux-Cotton hypothesized that sexual plasticity in crustaceans is mediated by primordial cells present in both sexes, which differentiate into an androgenic gland (AG) only in males. Although AG engraftments can masculinize genetic females, it remained unclear whether this reflects long-term integration of donor cells within the host or activation of host primordial AG progenitors. Using the freshwater prawn as an exceptional case of sexual plasticity, where AG-cell transfer yields functional neo-males bearing only female sex-chromosomes, we show, through cellular-resolution approaches, that the AG arises from primordial cells present in every individual, indicating autosomal machinery of sexual differentiation completely independent from the sex-chromosomes.

developmental biology↗

bioRxiv2025

Regional Signaling Controls Stem Cell-Mediated Regeneration in an Invertebrate Chordate

Many tissues harbor quiescent stem cells that activate after injury, yet how local signals regulate this transition is not well understood. The solitary ascidian Ciona robusta provides a unique model, as bottom body fragments regenerate while upper fragments fail to do so. By comparing these regenerative and non-regenerative contexts, we reveal striking differences in transcriptional dynamics and signaling environments. Combining flow cytometry, scRNA-seq, transplantation, and fate mapping, we identified a candidate stem cell population with robust proliferative and differentiation potential following transplantation. However, regenerative capacity does not simply reflect stem cell abundance, but instead depends on region-specific signaling cues. Local expression of metabolic, immune and differentiation-related factors further underscores the importance of spatially distinct environments in shaping outcomes. Our findings show how a shared injury response can diverge into regeneration versus failure, highlighting principles that may be leveraged to enhance tissue repair in other systems.

developmental biology↗

bioRxiv2025

Germline stem cell isolation, lineage tracing, and aging in a protochordate

Germline stem cells (GSCs), the source of gametes, are the only stem cells capable of passing genes to future generations and are therefore considered units of natural selection. Yet, the factors that influence GSC fitness, and thus govern GSC competition, which exist in both protochordates and mammals, remain poorly understood. We studied how aging affects GSC fitness in the protochordate Botryllus schlosseri, an evolutionary crosspoint between invertebrates and vertebrates. GSCs were isolated and distinguished from developing and mature gametes using flow cytometry and scRNA-Seq, facilitated by a new PacBio genome assembly. Moreover, their function was validated through a novel lineage tracing approach that combines membrane-labeled GSC transplantation with scRNA-Seq. Leveraging our method to isolate them, single-cell transcriptomics showed significant age-related changes between young and old GSCs. Spermatids and sperm, however, showed minimal changes, suggesting that reproductive aging is governed by GSCs rather than by gametes. Reduced expressions of markers like DDX4 and PIWIL1 in aged GSCs mirrored trends in mammalian datasets, pointing to a conserved GSC-driven aging mechanism across chordate evolution. This study provides new techniques that lay the foundation to investigate further drivers of GSC fitness and highlights fertility-related genes as promising targets for therapies to preserve reproductive health.

cell biology↗

bioRxiv2025

Explosive cytotoxicity of 'ruptoblasts' bridges hormonal surveillance and immune defense

Current understanding of cytotoxic immunity is shaped by hematopoietic-derived cells - T cells, natural killer cells, and neutrophils. Here, we identify ruptoblasts, a previously unknown cytotoxic glandular cell type in regenerative planarian flatworms. Ruptoblasts undergo an explosive cell death, ruptosis, triggered by activin, a multifunctional hormone that also acts as an inflammatory cytokine. Excessive activin - induced through protein injection, genetic chimerism, or bacterial infection - initiates ruptosis, discharging potent diffusible cytotoxic agents capable of eliminating any nearby cells, bacteria, and even mammalian cells within minutes. Ruptoblast ablation suppresses inflammation but compromises bacterial clearance, highlighting their broad-spectrum immune functions. Mechanistically distinct from known cytotoxic mechanisms, the explosive nature of ruptosis relies on intracellular calcium and dynamic cytoskeletal reorganization. Ruptoblast-like cells appear conserved in diverse basal bilaterians, implying an ancient evolutionary origin. These findings unveil a widespread strategy coupling hormonal regulation with immune defense and expand the landscape of evolutionary immune innovations.

immunology↗

bioRxiv2025

Functional characterization of immune cells in a cnidarian reveals an ancestral antiviral program

Examining early-branching animal phyla can help reconstructing the evolutionary origins of immune cells. Here, we characterized immune-related cell programs in embryos of the sea anemone Nematostella vectensis, a model of Cnidaria, which diverged [~]600 million years ago from other animals. Using a transgenic Nematostella reporter line expressing mCherry under the RLRb antiviral promoter, we identified a morphologically and transcriptomically distinct cell population activated by the viral mimic poly(I:C). These cells upregulate immune effector and regulator genes and show increased phagocytic activity. Bulk RNA sequencing of RLRb expressing cells and single-cell transcriptomics revealed gene regulatory programs expressed in specialized immune cells under basal conditions and upon activation. Comparing the Nematostella immune expression profile with that of stony corals treated with the immunostimulant 2'3'-Cyclic GMP-AMP demonstrated a conserved immune response across Hexacorallia. This study uncovers a novel cnidarian immune cell type involved in antiviral immunity, providing insights into the evolutionary history of innate immunity.

evolutionary biology↗

bioRxiv2022

P681 mutations within the polybasic motif of spike dictate fusogenicity and syncytia formation of SARS CoV-2 variants

The rapid spread and dominance of the Omicron SARS-CoV-2 over its Delta variant has posed severe global challenges. While extensive research on the role of the Receptor Binding Domain on viral infectivity and vaccine sensitivity has been documented, the role of the spike 681PRRAR/SV687 polybasic motif is less clear. Here we monitored infectivity and vaccine sensitivity of Omicron SARS-CoV-2 pseudovirus against sera samples that were drawn four months post administration of the third dose of BNT162b2 mRNA vaccine. Our findings show that relative to Wuhan-Hu and Delta SARS-CoV-2, Omicron displayed enhanced infectivity and a sharp decline in its sensitivity to vaccine-induced neutralizing antibodies. Furthermore, while the spike proteins form Wuhan-Hu (P681), Omicron (H681) and BA.2 (H681) pseudoviruses modestly promoted cell fusion and syncytia formation, Delta spike (P681R) displayed enhanced fusogenic activity and syncytia formation capability. Live-viruses plaque formation assays confirmed these findings and demonstrated that relatively to the Wuhan-Hu and Omicron SARS-CoV-2, Delta formed more plaques that were smaller in size. Introducing a single P681R point mutation within the Wuhan-Hu spike, or H681R within Omicron spike, restored fusion potential to similar levels observed for Delta spike. Conversely, a R681P point mutation within Delta spike efficiency abolished fusion potential. We conclude that over time, the efficiency of the third dose of the Pfizer vaccine against SARS CoV-2 is waned, and cannot neutralize Omicron. We further verify that the P681 position of the viral spike dictates fusogenicity and syncytia formation.

microbiology↗

bioRxiv2021

Heterologous reporter expression in the planarian Schmidtea mediterranea through somatic mRNA transfection

Planarians have long been studied for their regenerative abilities. Moving forward, tools for ectopic expression of non-native proteins will be of substantial value. Using a luminescent reporter to overcome the strong autofluorescence background of planarian tissues, we demonstrate heterologous protein expression in planarian cells and live animals. Our approach is based on the introduction of mRNA through several nanotechnological and chemical transfection methods. We improve reporter expression by altering untranslated region (UTR) sequences and codon bias, facilitating measurement of expression kinetics both in isolated cells and in whole planarians using luminescence imaging. We also examine protein expression as a function of variations in the UTRs of delivered mRNA, demonstrating a framework to investigate gene regulation at the post-transcriptional level. Together, these advances expand the toolbox for the mechanistic analysis of planarian biology and establish a strong foundation for the development and expansion of transgenic techniques in this unique model system. MotivationThe study of planarians has contributed to advances in our understanding of regeneration, stem cell dynamics, and many other fundamental biological processes. However, the persistent challenge of expressing transgenes in planarians has led to the speculation that they may be resistant to transfection. In this work, we develop methods to express exogenous mRNAs in both isolated planarian cells and whole animals by optimizing delivery techniques, genetic constructs, and detection methods. These methods allow us to study transfection kinetics and post-transcriptional regulation of gene expression in a quantitative manner. Beyond planarian research, this work should also provide a broadly applicable strategy to develop similar tools for animals that are also challenging to modify genetically.

bioengineering↗

bioRxiv2020

Global Age-Specific Patterns of Cyclic Gene Expression Revealed by Tunicate Transcriptome Atlas

Expression levels of circadian clock genes, which regulate 24-hour rhythms of behavior and physiology, have been shown to change with age. However, a study holistically linking aging and circadian gene expression is missing. Using the colonial chordate Botryllus schlosseri, we combined transcriptome sequencing and stem cell-mediated aging phenomena to test how circadian gene expression changes with age. This revealed that B. schlosseri clock and clock-controlled genes oscillate organism-wide, with daily, age-specific amplitudes and frequencies. These age-related, circadian patterns persist at the tissue level, where dramatic variations in cyclic gene expression of tissue profiles link to morphological and cellular aging phenotypes. Similar cyclical expression differences were found in hundreds of pathways associated with known hallmarks of aging, as well as pathways that were not previously linked to aging. The atlas we developed points to alterations in circadian gene expression as a key regulator of aging. One Sentence SummaryThe Ticking Clock: Systemic changes in circadian gene expression correlates with wide-ranging phenotypes of aging

developmental biology↗

bioRxiv2019

Molecular and Morphological Signatures of Chordate Development: Two Distinct Pathways, One Tunicate

All chordates, including urochordates such as tunicates, develop through embryogenesis. The chordate larvae of colonial tunicates metamorphose to lose all chordate structures such as notochord, neural tube, segmented musculature, and then develop by asexual reproduction [blastogenesis], whereby stem cells form tissues and organs. These two developmental pathways establish the same body axis, morphogenetic patterning and organ formation. It is unknown if this convergent morphology implies convergent cellular and molecular mechanisms, and whether the stem cells that mediate these processes differ. Using the colonial tunicate Botryllus schlosseri, we combined transcriptome sequencing and multiple microscopy techniques to study the molecular and morphological signatures of cells at each developmental stage of embryogenesis and blastogenesis. This revealed that the molecular programs are distinct, but the blastogenic tissue-specific stem cells and embryonic precursor populations share similar molecular profiles. By comparing embryogenesis in other chordates we found shared developmental principles, highlighting transcription factors as key evolutionary conserved elements. This study establishes a platform for advancing the science of stem cell biology and regulation of development and regeneration.

developmental biology↗

bioRxiv2017

Evolutionary Origin of the Mammalian Hematopoietic System Found in a Colonial Chordate

Hematopoiesis is an essential process that evolved in multicellular animals. At the heart of this process are hematopoietic stem cells (HSCs), which are multipotent, self-renewing and generate the entire repertoire of blood and immune cells throughout life. Here we studied the hematopoietic system of Botryllus schlosseri, a colonial tunicate that has vasculature, circulating blood cells, and interesting characteristics of stem cell biology and immunity. Self-recognition between genetically compatible B. schlosseri colonies leads to the formation of natural parabionts with shared circulation, whereas incompatible colonies reject each other. Using flow-cytometry, whole-transcriptome sequencing of defined cell populations, and diverse functional assays, we identified HSCs, progenitors, immune-effector cells, the HSC niche, and demonstrated that self-recognition inhibits cytotoxic reaction. Our study implies that the HSC and myeloid lineages emerged in a common ancestor of tunicates and vertebrates and suggests that hematopoietic bone marrow and the B. schlosseri endostyle niche evolved from the same origin.

immunology↗