Biology subjects

Madelaine, R.

Publications and source records attributed to Madelaine, R..

8 recordsLinked to original sources

bioRxiv2026

Apelin signaling controls neuroendocrine homeostasis via Atoh8-dependent transcriptional regulation

Apelin is a pleiotropic peptide hormone with established roles in cardiovascular function, angiogenesis, and metabolism, but its contribution to neuroendocrine development and function remains poorly understood. Here, using genetic loss-of-function and inducible gain-of-function approaches in zebrafish, we show that Apelin signaling is dosage-sensitive and required for normal development, reproductive capacity, and physiological homeostasis. Both apelin deficiency and apelin overexpression disrupted embryonic development and reduced adult lifespan, while exhibiting markedly reduced fertility in both sexes. Transcriptomic profiling revealed broad changes in neuroendocrine, hormonal, stress-response, and inflammatory genes with young adult mutant expression profiles resembling those of aged wild-type fish. Both loss and excess of Apelin also disrupted hypothalamic-pituitary-thyroid (HPT) axis development, reducing hypothalamic thyrotropin-releasing hormone-expressing cells, pituitary gonadotropic cell populations, and thyroid gland volume. Transcriptomic analyses identified atoh8, encoding a basic helix-loop-helix transcription factor, as a candidate effector of Apelin signaling. Apelin expression increased atoh8 expression during early embryogenesis, whereas atoh8 mRNA partially rescued developmental defects in apelin mutants, including hypothalamic and pituitary markers, and thyroid volume. Conversely, atoh8 crispants displayed thyroid and pituitary abnormalities, supporting a role for Atoh8 in neuroendocrine development. Together, these findings establish Apelin signaling as a dosage-sensitive regulator of zebrafish development and tissue homeostasis and identify Atoh8 as a functional downstream effector that partially mediates Apelin-dependent HPT axis formation. This work links peptide hormone signaling to neuroendocrine development and provides a framework for investigating its broader contributions to vertebrate physiology, reproduction and aging.

developmental biology↗

bioRxiv2026

Mesenchymal-derived neural progenitors underlie local insulin production and neuronal transdifferentiation during retina regeneration

In humans, retinal-neuron death, optic-nerve injuries, and associated neurodegenerative diseases, such as glaucoma and age-related macular degeneration, often lead to permanent vision loss. While the capacity for regeneration is low in the human nervous system, including the retina, some non-mammalian vertebrate species, including zebrafish, are capable of endogenous neuronal regeneration after injury. Unlike mammals, zebrafish do not form a scar that inhibits axonal and neuronal regeneration after injury. Rather, they harbor neural progenitor and stem-cell populations allowing regeneration of entire parts of the nervous system and restoration of tissue integrity and function. In the zebrafish retina, cycling neural progenitor cells of the ciliary marginal zone and quiescent resident neural stem cells (the latter of which are also called Muller glial cells) participate in neuronal regeneration following different types of injury. In this study, we report the identification of a novel, additional cellular source participating in neuronal regeneration of neurons in the zebrafish retina after genetic ablation of retinal ganglion cells. Before injury, these progenitor cells express molecular markers of neural-crest-cell and/or fibroblast identity, such as sox10, pdgfrb, and eya2, while after neuronal ablation they also express proneural factors including the ascl1a and olig2 genes. Combining genetic ablation of neurons with photoconversion or Cre/Lox-dependent genetic lineage tracing of sox10-expressing cells, we demonstrated that these cells can differentiate into post-mitotic retinal neurons in the ganglion cell layer (GCL) in the absence of cell proliferation. We also showed, surprisingly, that this progenitor population locally produces insulin mRNA, and that insulin signaling is involved in the accumulation of mesenchymal-derived neural progenitors in the GCL and in their subsequent transdifferentiation into RGCs. This work reveals an unexpected and novel cellular mechanism of transdifferentiation, dependent on a neural-crest-derived mesenchymal cell population, participating in neuronal regeneration in the zebrafish retina. The discovery of this plastic cell population could potentially lead to new strategies to promote the formation of new neurons in the mammalian retina.

developmental biology↗

bioRxiv2026

Sexually Dimorphic Response to Dietary Restriction-induced Longevity and Muscle Rejuvenation in Nothobranchius furzeri.

Age-related skeletal muscle decline (sarcopenia) is a major contributor to frailty and mortality during aging, yet the extent to which sex shapes muscle aging and its response to dietary interventions remains poorly understood. Here, we use the short-lived vertebrate Nothobranchius furzeri (African turquoise killifish; ATK) to investigate how sex and intermittent fasting (IF) interact to regulate lifespan and skeletal-muscle aging. We establish and optimize an IF regimen that significantly extends lifespan in both male and female killifish, albeit with classical trade-offs including reduced growth and reproductive output. Despite these costs, IF markedly improves swimming performance in aged animals of both sexes. Structural analyses of killifish on a normal diet reveal pronounced sexual dimorphism in muscle aging. Males exhibit age-associated myofiber hyperplasia, whereas females maintain fiber number but undergo hypertrophic remodeling. IF partially reverses both phenotypes, restoring a more youthful fiber size distribution in both males and females. Single-nucleus RNA sequencing uncovers sex-specific remodeling of muscle-fiber composition in killifish on a normal diet, with females displaying an age-associated shift toward oxidative slow-twitch fibers that is reversed by IF, while males show relatively stable fiber-type proportions under normal and IF feeding regimens. Cell-cell communication analyses further reveal a global decline in intercellular signaling with age, alongside sex-specific restoration of distinct pathways under IF, including axon guidance and IGF signaling in females and metabolic ANGPTL signaling in males. Finally, bulk transcriptomic profiling demonstrates that aging follows largely sexually dimorphic molecular trajectories, whereas IF induces both sex-specific and shared responses. Notably, under IF, both sexes exhibit upregulation of ribosome biogenesis and genes supporting myofibrillar organization and contraction, likely underlying preserved muscle function. Together, these findings demonstrate that IF promotes longevity and muscle health through conserved anabolic mechanisms alongside sex-specific cellular and molecular rejuvenation strategies. Our work highlights the importance of incorporating sex as a biological variable when designing dietary interventions to promote healthy aging.

physiology↗

bioRxiv2025

Zebrafish genetic model of neuromuscular degeneration associated with Atrogin-1 expression

The degenerative loss of muscle associated with aging leading to muscular atrophy is called sarcopenia. Currently, practicing regular physical exercise is the only efficient way to delay sarcopenia onset. Identification of therapeutic targets to alleviate the symptoms of aging requires in vivo model organisms of accelerated muscle degeneration and atrophy. The zebrafish undergoes aging, with hallmarks including mitochondrial dysfunction, telomere shortening, and accumulation of senescent cells. However, zebrafish age slowly, and no specific zebrafish models of accelerated muscle atrophy associated with molecular events of aging are currently available. We have developed a new genetic tool to efficiently accelerate muscle-fiber degeneration and muscle-tissue atrophy in zebrafish larvae and adults. We used a gain-of-function strategy with a molecule that has been shown to be necessary and sufficient to induce muscle atrophy and a sarcopenia phenotype in mammals: Atrogin-1 (also named Fbxo32). We report the generation, validation, and characterization of a zebrafish genetic model of accelerated neuromuscular atrophy, the atrofish. We demonstrated that Atrogin-1 expression specifically in skeletal muscle tissue induces a muscle atrophic phenotype associated with locomotion dysfunction in both larvae and adult fish. We identified degradation of the myosin light chain as an event occurring prior to muscle-fiber degeneration. Biological processes associated with muscle aging such as proteolysis, inflammation, stress response, extracellular matrix (ECM) remodeling, and apoptosis are upregulated in the atrofish. Surprisingly, we observed a strong correlation between muscle-fiber degeneration and reduced numbers of neuromuscular junctions in the peripheral nervous system, as well as neuronal cell bodies in the spinal cord, suggesting that muscle atrophy could underly a neurodegenerative phenotype in the central nervous system. Finally, while atrofish larvae can recover locomotive functions, adult atrofish have impaired regenerative capacities, as is observed in mammals during muscle aging. In the future, the atrofish could serve as a platform for testing molecules aimed at treating or alleviating the symptoms of muscle aging, thereby opening new therapeutic avenues in the fight against sarcopenia.

developmental biology↗

bioRxiv2025

The small molecule ML233 is a direct inhibitor of tyrosinase function

Melanogenesis is the biological process regulating the synthesis of melanin pigments in melanocytes. Defective melanogenesis is associated with numerous human skin diseases, including, but not limited to, albinism, vitiligo, melasma, and hypo- and hyperpigmentation disorders. Tyrosinase is the rate-limiting enzyme controlling melanogenesis, and hence tremendous efforts have been made to identify potent and safe inhibitors of tyrosinase function. However, despite decades of research, currently there is no effective treatment that inhibits melanogenesis or tyrosinase activity with no adverse side effects. In this study, we report characterization of the ML233 chemical as a potent inhibitor of tyrosinase activity in vivo and in vitro. We demonstrate that ML233 reduces melanin production in the zebrafish model with no observable significant toxic side effects, and in murine melanoma cells. We also predict that these effects are mediated through direct tyrosinase-ML233 interaction, i.e., binding of the ML233 molecule to the active site of the protein to inhibit its function. Together, our results reveal that ML233 plays roles in both healthy and pathological skin cells via inhibition of melanin production. ML233-mediated tyrosinase inhibition is a potentially safe and effective approach to alleviate the symptoms of melanocyte-associated diseases and thereby substantially improve human health.

pharmacology and toxicology↗

bioRxiv2024

Leukemia-derived apelin selects endothelial niche clones to promote tumorigenesis

Hematopoietic stem cells are regulated by endothelial and mesenchymal stromal cells in the marrow niche1-3. Leukemogenesis was long believed to be solely driven by genetic perturbations in hematopoietic cells but introduction of genetic mutations in the microenvironment demonstrated the ability of niche cells to drive disease progression4-8. The mechanisms by which the stem cell niche induces leukemia remain poorly understood. Here, using cellular barcoding in zebrafish, we found that clones of niche endothelial and stromal cells are significantly expanded in leukemic marrows. The pro-angiogenic peptide apelin secreted by leukemic cells induced sinusoidal endothelial cell clonal selection and transcriptional reprogramming towards an angiogenic state to promote leukemogenesis in vivo. Overexpression of apelin in normal hematopoietic stem cells led to clonal amplification of the niche endothelial cells and promotes clonal dominance of blood cells. Knock-out of apelin in leukemic zebrafish resulted in a significant reduction in disease progression. Our results demonstrate that leukemic cells remodel the clonal and transcriptional landscape of the marrow niche to promote leukemogenesis and provide a potential therapeutic opportunity for anti-apelin treatment.

cancer biology↗

bioRxiv2019

Morphogenesis is transcriptionally coupled to neurogenesis during olfactory placode development

Sense organs acquire their distinctive shapes concomitantly with the differentiation of sensory cells and neurons necessary for their function. While our understanding of the mechanisms controlling morphogenesis and neurogenesis in these structures has grown, how these processes are coordinated remains largely unexplored. Neurogenesis in the zebrafish olfactory epithelium requires the bHLH proneural transcription factor Neurogenin1 (Neurog1). To address whether Neurog1 also controls morphogenesis in this system, we analysed the morphogenetic behaviour of early olfactory neural progenitors in neurog1 mutant embryos. Our results indicate that the oriented movements of these progenitors are disrupted in this context. Morphogenesis is similarly affected by mutations in the chemokine receptor gene, cxcr4b, suggesting it is a potential Neurog1 target gene. We find that Neurog1 directly regulates cxcr4b through an E-boxes cluster located just upstream of the cxcr4b transcription start site. Our results suggest that proneural transcription factors, such as Neurog1, directly couple distinct aspects of nervous system development. One Sentence SummaryNeurog1 controls olfactory organ morphogenesis via cxcr4b

developmental biology↗

bioRxiv2017

Cell-type heterogeneity in the zebrafish olfactory placode is generated from progenitors within preplacodal ectoderm

Vertebrate olfactory placodes consists of a variety of neuronal populations, which are thought to have distinct embryonic origins. In the zebrafish, while ciliated sensory neurons arise from preplacodal ectoderm (PPE), previous lineage tracing studies suggest that both Gonadotropin releasing hormone 3 (Gnrh3) and microvillous sensory neurons derive from cranial neural crest (CNC). We find that the expression of Islet1/2 is restricted to Gnrh3 neurons associated with the olfactory placode. Unexpectedly, however, we find no change in Islet1/2+ cell numbers in sox10 mutant embryos, calling into question their CNC origin. Lineage reconstruction based on backtracking in time-lapse confocal datasets, and confirmed by photoconversion experiments, reveals that Gnrh3 neurons derive from the anterior/medial PPE. Similarly, all of the microvillous sensory neurons we have traced arise from preplacodal progenitors. Our results suggest that rather than originating from separate ectodermal populations, cell-type heterogeneity is generated from overlapping pools of progenitors within the preplacodal ectoderm.

developmental biology↗