Biology subjects

Deryckere, A.

Publications and source records attributed to Deryckere, A..

8 recordsLinked to original sources

bioRxiv2025

A conserved logic for the development of cortical layering in tetrapods

The cerebral cortex is part of the pallium, a brain region conserved across vertebrates yet remarkably diverse in structure and cellular composition. A defining feature of the cerebral cortex is its organization into neuronal layers with distinct gene expression profiles, input-output connectivity, and function. According to prevailing models, the cerebral cortex emerged in ancestral amniotes (mammals and reptiles) following innovations in pallial development that enabled the generation of diverse neuron types and their laminar organization.1-11 However, little is known about pallial development and architecture in amphibians, the sister group of amniotes. Here we show that in the salamander Pleurodeles waltl, the dorsal pallium is organized in distinct superficial and deep layers with neurons that develop following cellular and molecular principles of mammalian corticogenesis. Using birthdating analysis, barcode-based lineage tracing, and single-cell RNA sequencing, we find that radial glia temporal states and intermediate progenitor cells are conserved across species, while neuronal differentiation trajectories are highly evolvable. Neurons generated at different developmental time points occupy different layers and exhibit distinct molecular and projection identities. Thus, temporally-patterned neurogenesis represents an ancient organizing principle of layered pallia, although mammals display an inverted layer order along the radial axis. Together, these findings demonstrate that the core developmental principles underlying cortical layering - including temporal patterning, intermediate progenitors, and laminar organization - predate the origin of amniotes. Our results suggest that the evolutionary expansion of the mammalian neocortex built upon a deeply conserved developmental framework already present in early tetrapods.

developmental biology↗

bioRxiv2025

Evolution of Cajal-Retzius Cells in Vertebrates from an Ancient Class of Tp73+ Neurons

Evolutionary changes of cortical development were instrumental for the emergence of the mammalian neocortex. Cajal-Retzius cells, a transient neuron type discovered over a century ago, are critical players in the development of mammalian-specific cortical features such as inside-out corticogenesis. However, it is unclear whether Cajal-Retzius cells exist only in mammals, or if they are ancestral in vertebrates but acquired new functions during mammalian brain development. To trace the evolution of this cell type, we probe the presence of Cajal-Retzius cells in chicken, salamander, zebrafish, and little skate. First, through comparative transcriptomics and spatial analysis we show that Cajal-Retzius cells are conserved in vertebrates. However, only amniote Cajal-Retzius cells gained robust expression of Reelin, a secreted glycoprotein crucial for mammalian cortical development. Second, we find that Cajal-Retzius cells are part of a larger and diverse family of neuron types, and are closely related to Tp73+ external tufted cells in the olfactory bulb, which express most of the "canonical" Cajal-Retzius transcription factors. Our results indicate that Cajal-Retzius cells emerged early in vertebrate history, using a regulatory program largely shared with neurons in the olfactory system, and that transcriptomic novelties underlie their specialized roles in mammalian cortical development. This is an extreme example of how cell types may diverge in morphology and function over the course of evolution even when their core transcriptomic profile is broadly preserved.

neuroscience↗

bioRxiv2024

Adeno-Associated Viral Tools to Trace Neural Development and Connectivity Across Amphibians

The development, evolution, and function of the vertebrate central nervous system (CNS) can be best studied using diverse model organisms. Amphibians, with their unique phylogenetic position at the transition between aquatic and terrestrial lifestyles, are valuable for understanding the origin and evolution of the tetrapod brain and spinal cord. Their metamorphic developmental transitions and unique regenerative abilities also facilitate the discovery of mechanisms for neural circuit remodeling and replacement. The genetic toolkit for amphibians, however, remains limited, with only a few species having sequenced genomes and a small number of transgenic lines available. In mammals, recombinant adeno-associated viral vectors (AAVs) have become a powerful alternative to genome modification for visualizing and perturbing the nervous system. AAVs are DNA viruses that enable neuronal transduction in both developing and adult animals with low toxicity and spatial, temporal, and cell-type specificity. However, AAVs have never been shown to transduce amphibian cells efficiently. To bridge this gap, we established a simple, scalable, and robust strategy to screen AAV serotypes in three distantly-related amphibian species: the frogs Xenopus laevis and Pelophylax bedriagae, and the salamander Pleurodeles waltl, in both developing larval tadpoles and post-metamorphic animals. For each species, we successfully identified at least two AAV serotypes capable of infecting the CNS; however, no pan-amphibian serotype was identified, indicating rapid evolution of AAV tropism. In addition, we developed an AAV-based strategy that targets isochronic cohorts of developing neurons - a critical tool for parsing neural circuit assembly. Finally, to enable visualization and manipulation of neural circuits, we identified AAV variants for retrograde tracing of neuronal projections in adult animals. Our findings expand the toolkit for amphibians to include AAVs, establish a generalizable workflow for AAV screening in non-canonical research organisms, generate testable hypotheses for the evolution of AAV tropism, and lay the foundation for modern cross-species comparisons of vertebrate CNS development, function, and evolution.

neuroscience↗

bioRxiv2022

Glutamatergic neuron types in the amygdala of the urodele amphibian Pleurodeles waltl

The amygdala is a complex brain structure in the vertebrate telencephalon, essential for regulating social behaviors, emotions and (social) cognition. In contrast to the vast majority of neuron types described in the many nuclei of the mammalian amygdala, little is known about the neuronal diversity in non-mammals, making reconstruction of its evolution particularly difficult. Here, we characterize glutamatergic neuron types in the amygdala of the salamander Pleurodeles waltl. Our single-cell RNA sequencing data indicate the existence of at least ten distinct types and subtypes of glutamatergic neurons in the salamander amygdala. In situ hybridization for marker genes indicates that these neuron types are located in three major subdivisions: the lateral amygdala, the medial amygdala, and a newly-defined area demarcated by high expression of the transcription factor Sim1. The gene expression profiles of these neuron types suggest similarities with specific neuron types in the sauropsid and mammalian amygdala, and in particular the evolutionary conservation of Sim1-expressing amygdalar neurons in tetrapods. Taken together, our results reveal a surprising diversity of glutamatergic neuron types in the amygdala of salamanders, despite the anatomical simplicity of their brain.

neuroscience↗

bioRxiv2022

Cell type profiling in salamanders identifies innovations in vertebrate forebrain evolution

The evolution of advanced cognition in vertebrates is associated with two independent innovations in the forebrain: the six-layered neocortex in mammals and the dorsal ventricular ridge (DVR) in sauropsids (reptiles and birds). How these novelties arose in vertebrate ancestors remains unclear. To reconstruct forebrain evolution in tetrapods, we built a cell type atlas of the telencephalon of the salamander Pleurodeles waltl. Our molecular, developmental, and connectivity data indicate that parts of the sauropsid DVR trace back to tetrapod ancestors. In contrast, the salamander dorsal pallium is devoid of cellular and molecular characteristics of the mammalian neocortex, yet shares similarities with entorhinal cortex and subiculum. Our findings chart the series of innovations that resulted in the emergence of the sauropsid DVR, and the mammalian six-layered neocortex.

neuroscience↗

bioRxiv2022

Cell type diversity in a developing octopus brain

Octopuses are mollusks that have evolved intricate neural systems comparable with vertebrates in terms of cell number, complexity and size. The cell types within the octopus brain that control their amazingly rich behavioral repertoire are still unknown. Here we profile cell diversity of the paralarval Octopus vulgaris brain to build a comprehensive cell type atlas that comprises mostly neural cells, as well as multiple glial subtypes, endothelial cells and fibroblasts. Moreover, we spatially map cell types within the octopus brain, including vertical and optic lobe cell types. Investigation of cell type conservation reveals a shared gene signature between glial cells of mice, fly and octopus. Genes related to learning and memory are enriched in vertical lobe cells, which show molecular similarities with Kenyon cells in Drosophila. Taken together, our data sheds light on cell type diversity and evolution of the complex octopus brain. Highlights & Key findingsO_LICharacterization of different cell types present in the early paralarval brain C_LIO_LICross-species comparisons reveal a conserved glial gene expression signature C_LIO_LIVertical lobe amacrine cells in octopus have molecular similarities to fly Kenyon cells C_LIO_LIHomeobox genes are defining transcription factors for cell type identity C_LIO_LIRecently expanded gene families may underlie cellular diversification C_LI

developmental biology↗

bioRxiv2021

Identification of neural progenitor cells and their progeny reveals long distance migration in the developing octopus brain

Cephalopods have evolved nervous systems that parallel the complexity of mammalian brains in terms of neuronal numbers and richness in behavioral output. How the cephalopod brain develops has only been described at the morphological level, and it remains unclear where the progenitor cells are located and what molecular factors drive neurogenesis. Using histological techniques, we located dividing cells, neural progenitors and postmitotic neurons in Octopus vulgaris embryos. Our results indicate that progenitors are located outside the central brain cords in the lateral lips adjacent to the eyes, suggesting that newly formed neurons migrate into the cords. Lineage tracing experiments then showed that progenitors, depending on their location in the lateral lips, generate neurons for the different lobes. The finding that octopus newborn neurons migrate over long distances is reminiscent of vertebrate neurogenesis and suggests it might be a fundamental strategy for large brain development.

developmental biology↗

bioRxiv2020

A practical staging atlas to study embryonic development of Octopus vulgaris under controlled laboratory conditions

BackgroundOctopus vulgaris has been an iconic cephalopod species for neurobiology research as well as for cephalopod aquaculture. It is one of the most intelligent and well-studied invertebrates, possessing both long- and short-term memory and the striking ability to perform complex cognitive tasks. Nevertheless, how the common octopus developed these uncommon features remains enigmatic. O. vulgaris females spawn thousands of small eggs and remain with their clutch during their entire development, cleaning, venting and protecting the eggs. In fact, eggs incubated without females usually do not develop normally, mainly due to biological contamination (fungi, bacteria, etc.). This high level of parental care might have hampered laboratory research on the embryonic development of this intriguing cephalopod. ResultsHere, we present a completely parameter-controlled artificial seawater standalone egg incubation system that replaces maternal care and allows successful embryonic development of a small-egged octopus species until hatching in a laboratory environment. We also provide a practical and detailed 1 staging atlas based on bright-field and light sheet fluorescence microscopy imaging for precise monitoring of embryonic development. The atlas has a comparative section to benchmark stages to the different scales published by Naef (1928), Arnold (1965) and Boletzky (2016). Finally, we provide methods to monitor health and wellbeing of embryos during organogenesis. ConclusionBesides introducing the study of O. vulgaris embryonic development to a wider community, this work can be a high-quality reference for comparative evolutionary developmental biology.

developmental biology↗