Biology subjects

Formery, L.

Publications and source records attributed to Formery, L..

5 recordsLinked to original sources

bioRxiv2025

Major cell type differences between larval and adult hemichordate body plans

A major gap in our understanding of animal development is how adult body plans arise in animals with indirect development, where adults emerge from the transformation of a distinct larval form during metamorphosis. We address this question by examining cellular changes in the enteropneust hemichordate Schizocardium californicum, a species with a complex lifecycle and dramatic metamorphosis. Employing whole-body single-cell RNA sequencing, we chart the cellular composition and transcriptional dynamics of larval, metamorphosis, and adult stages. Our tissue level atlas reveals that ectodermal and endodermal cell types in larvae and adults occupy distinct transcriptional spaces, showing greater similarity to other cell types within the same life stage than to their counterparts in the opposite stage. In contrast, mesodermal cell types from both larvae and adults cluster closely together, indicating conserved transcriptional profiles. These findings demonstrate that the extensive morphological reorganization during metamorphosis is paralleled by profound shifts in cell-type specific transcriptional programs, highlighting the complexity of the larva-to-adult transition.

developmental biology↗

bioRxiv2025

Antero-posterior patterning in the brittle star Amphipholis squamata and the evolution of body plans across echinoderms

Although the adult pentaradial body plan of echinoderms evolved from a bilateral ancestor, identifying axial homologies between the morphologically divergent echinoderms and their bilaterian relatives has been an enduring problem in zoology. The expression of conserved bilaterian patterning genes in echinoderms provides a molecular framework for resolving this puzzle. Recent studies in juvenile asteroids suggest that the bilaterian antero-posterior axis maps onto the medio-lateral axis that is perpendicular to each of the five rays of the pentaradial body plan. Here we test this hypothesis in another echinoderm class, the ophiuroids, using the cosmopolitan brittle star Amphipholis squamata. Our results show that the general principles of axial patterning are similar to those described in asteroids, and comparisons with existing molecular data from other echinoderm taxa support the idea that medio-lateral deployment of the AP patterning program across the rays predates the evolution of the asterozoan and likely the echinoderm crown-groups. Our data also reveal expression differences between A. squamata and asteroids, which we attribute to secondary modifications specific to ophiuroids. Together, this work provides important comparative data to reconstruct the evolution of axial properties in echinoderm body plans.

evolutionary biology↗

bioRxiv2024

See-Star: a versatile hydrogel-based protocol for clearing large, opaque and calcified marine invertebrates

Studies of morphology and developmental patterning in adult stages of many invertebrates are hindered by opaque structures, such as shells, skeletal elements, and pigment granules that block or refract light and necessitate sectioning for observation of internal features. An inherent challenge in studies relying on surgical approaches is that cutting tissue is semi-destructive, and delicate structures, such as axonal processes within neural networks, are computationally challenging to reconstruct once disrupted. To address this problem, we developed See-Star, a hydrogel-based tissue clearing protocol to render the bodies of opaque and calcified invertebrates optically transparent while preserving their anatomy in an unperturbed state, facilitating molecular labeling and observation of intact organ systems. The resulting protocol can clear large (>1 cm3) specimens to enable deep-tissue imaging, and is compatible with molecular techniques, such as immunohistochemistry and in situ hybridization to visualize protein and mRNA localization. To test the utility of this method, we performed a whole mount imaging study of intact nervous systems in juvenile echinoderms and molluscs, and demonstrate that See-Star allows for comparative studies to be extended far into development facilitating insights into the anatomy of juveniles and adults that are usually not amenable to whole mount imaging.

developmental biology↗

bioRxiv2024

Algorithmic construction of topologically complex biomineral lattices via cellular syncytia

Biomineralization is ubiquitous in both unicellular and multicellular living systems [1, 2] and has remained elusive due to a limited understanding of physicochemical and biomolecular processes [3]. Echinoderms, identified with diverse architectures of calcite-based structures in the dermis[4], present an enigma of how cellular processes control shape and form of individual structures. Specifically, in holothurians (sea cucumbers), multi-cellular clusters construct discrete single-crystal calcite ossicles ([~] 100 {micro}m length scale), with diverse morphologies both across species and even within an individual animal [5]. The local rules that might encode these unique morphologies in calcite ossicles in holothurians remain largely unknown. Here we show how transport processes in a cellular syncytium impart a top-down control on ossicle geometry via symmetry breaking, branching, and fusion in finite cellular clusters. As a unique example of cellular masonary, we show how coordination within a small cluster of cells builds calcite structures about an order of magnitude larger than any individual participating cell. We establish live imaging of ossicle growth in Apostichopus parvimensis juveniles revealing how individual crystalline seeds ([~] 1 - 2 {micro}m) grow inside a multi-cellular syncytial complex with the biomineral completely wrapped within a membrane-bound cytoplasmic sheath. Constructing a topological description of ossicle geometries from 3D micro-CT (computational tomography) data reveals the hidden growth history and conserved patterns across ossicle types. We further demonstrate vesicle transport on the surface of the ossicle, rather than cell motility, regulates material transport to the ossicle tips via a unique cytoskeletal architecture. Finally, using reduced order models of conserved transport on self-closing active branching networks, we highlight the hidden universality in the growth process of distinct ossicles. The system presented here serves as a unique playground merging top-down cellular physiology and classical branching morphogenesis [6] with bottom-up non-equilibrium mineralization [7] processes at the interface of living and non-living matter [8].

biophysics↗

bioRxiv2023

Molecular evidence of anteroposterior patterning in adult echinoderms

The origin of the pentaradial body plan of echinoderms from a bilateral ancestor is one of the most enduring zoological puzzles. Since echinoderms are defined by morphological novelty, even the most basic axial comparisons with their bilaterian relatives are problematic. Here, we used conserved antero-posterior (AP) axial molecular markers to determine whether the highly derived adult body plan of echinoderms masks underlying patterning similarities with other deuterostomes. To revisit this classical question, we used RNA tomography and in situ hybridizations in the sea star Patiria miniata to investigate the expression of a suite of conserved transcription factors with well-established roles in the establishment of AP polarity in bilaterians. We find that the relative spatial expression of these markers in P. miniata ambulacral ectoderm shows similarity with other deuterostomes, with the midline of each ray representing the most anterior territory and the most lateral parts exhibiting a more posterior identity. Interestingly, there is no ectodermal territory in the sea star that expresses the characteristic bilaterian trunk genetic patterning program. This suggests that from the perspective of ectoderm patterning, echinoderms are mostly head-like animals, and prompts a reinterpretation of the evolutionary trends that made echinoderms the most derived animal group.

developmental biology↗