Biology subjects

Clouthier, D. E.

Publications and source records attributed to Clouthier, D. E..

5 recordsLinked to original sources

bioRxiv2026

Dermal bone grows by cellular invasion and intercalary biomineralization

Dermal bone architecture bears great evolutionary significance for jawed vertebrates. Its thickness growth is believed to rely on matrix apposition by superficial osteoblasts. To test this hypothesis we employ genetic lineage mapping, conditional gene ablation, intravital matrix labelling and molecular 3D analysis at single cell resolution in vivo. We uncover an invasive mechanism incompatible with apposition. The pervasive arrangement of two layers sandwiching a third spongy layer develops from a molecularly defined bi-layer via a previously unknown developmental module: Outer layer osteoblasts form rosette-like assemblies around single invading cells. The latter bear unique molecular signatures and form de novo sheets inside the spongy layer, communicating with the layer below. The transcription factor Hand2 organizes this module by orchestrating rosette formation, their molecular heterogeneity, cellular invasion and spongy layer thickness growth. Surprisingly, invading osteoblasts secrete new biomineral matrix inside the older matrix, which keeps expanding. Such intercalary biomineralization provides new perspectives for bone biology and the evolution of endochondral ossification.

developmental biology↗

bioRxiv2026

Dermal bone remodelling by invasive osteoblasts evolved in stem gnathostomes

The evolutionary origin of the human face can be traced to the earliest vertebrates with a dermal skeleton in which canonical skeletal Issues and cell types arose. To elucidate its developmental evolution we performed genetic mosaic labelling, 3D single cell analysis and fluorescent matrix birthdating in vivo. We discover a common lineage origin of endothelial cells and osteoblasts and de novo vasculogenesis (not angiogenesis) as the dominant mechanism. Inside the spongy (cancellous) layer, invasive OPN+/RUNX2+ osteoblasts establish two orthogonal collagen sca[ff]olds, remodel them by directional secretion of matrix metalloproteinases and employ controllers of hydroxyapatite crystal resorption previously considered to be osteoclast- specific. Such intercalary biomineralization, comprising cellular sheet and volumetric biomineral expansion, renders all layers malleable even during postnatal stages. We trace this mechanism to bone ontogenies of the earliest skeletonizing vertebrates and resolve cell/Issue homologies controversial for almost two centuries. Our new model also has implications for bone matrix bioengineering and cancer osteomimicry that might replay some of these ontogenetic processes.

evolutionary biology↗

bioRxiv2024

The Gq/11 family of Gα subunits is necessary and sufficient for lower jaw development

Vertebrate jaw development is coordinated by highly conserved ligand-receptor systems such as the peptide ligand Endothelin 1 (Edn1) and Endothelin receptor type A (Ednra), which are required for patterning of lower jaw structures. The Edn1/Ednra signaling pathway establishes the identity of lower jaw progenitor cells by regulating expression of numerous patterning genes, but the intracellular signaling mechanisms linking receptor activation to gene regulation remain poorly understood. As a first step towards elucidating this mechanism, we examined the function of the Gq/11 family of G subunits in zebrafish using pharmacological inhibition and genetic ablation of Gq/11 activity and transgenic induction of a constitutively active Gq protein in edn1-/- embryos. Genetic loss of Gq/11 activity fully recapitulated the edn1-/- phenotype, with genes encoding G11 being most essential. Furthermore, inducing Gq activity in edn1-/-embryos not only restored Edn1/Ednra-dependent jaw structures and gene expression signatures but also caused homeosis of the upper jaw structure into a lower jaw-like structure. These results indicate that Gq/11 is necessary and sufficient to mediate the lower jaw patterning mechanism for Ednra in zebrafish. Summary statementGq/11 is the signaling mediator downstream of Endothelin 1 and Endothelin Receptor Type A that drives tissue patterning for all lower jaw structures in zebrafish.

developmental biology↗

bioRxiv2021

GATA3 is essential for separating patterning domains during facial morphogenesis

Neural crest cells (NCCs) within the mandibular and maxillary portions of the first pharyngeal arch are initially competent to respond to signals from either region. However, mechanisms that are only partially understood establish developmental tissue boundaries to ensure spatially correct patterning. In the Hinge and Caps model of facial development, signals from both ventral prominences, referred to as the caps, pattern the adjacent tissues while the intervening region, known as the hinge, maintains separation of the mandibular and maxillary domains. One cap signal is GATA3, a member of the GATA family of zinc-finger transcription factors with a distinct expression pattern in the ventral-most part of the mandibular and maxillary portions of the first arch. Here we show that disruption of Gata3 in mouse embryos leads to hemifacial microsomia, facial bone hypoplasia and syngnathia (bony fusion of the upper and lower jaws). These changes are preceded by gene expression changes in post-migratory NCCs around the maxillomandibular junction (the hinge). GATA3 is thus a crucial component in establishing the network of factors that functionally separate the upper and lower jaws during development. Summary StatementLoss of Gata3 leads to BMP-mediated disruption of Fgf8 expression at the maxillomandibular junction during development, resulting in later fusion of the upper and lower jaws.

developmental biology↗

bioRxiv2020

Hand2 delineates mesothelium progenitors and is reactivated in mesothelioma

The mesothelium forms epithelial membranes that line the bodies cavities and surround the internal organs. Mesothelia widely contribute to organ homeostasis and regeneration, and their dysregulation can result in congenital anomalies of the viscera, ventral wall defects, and mesothelioma tumors. Nonetheless, the embryonic ontogeny and developmental regulation of mesothelium formation has remained uncharted. Here, we combine genetic lineage tracing, in toto live imaging, and single-cell transcriptomics in zebrafish to track mesothelial progenitor origins from the lateral plate mesoderm (LPM). Our single-cell analysis uncovers a post-gastrulation gene expression signature centered on hand2 that delineates distinct progenitor populations within the forming LPM. Combining gene expression analysis and imaging of transgenic reporter zebrafish embryos, we chart the origin of mesothelial progenitors to the lateral-most, hand2-expressing LPM and confirm evolutionary conservation in mouse. Our time-lapse imaging of transgenic hand2 reporter embryos captures zebrafish mesothelium formation, documenting the coordinated cell movements that form pericardium and visceral and parietal peritoneum. We establish that the primordial germ cells migrate associated with the forming mesothelium as ventral migration boundary. Functionally, hand2 mutants fail to close the ventral mesothelium due to perturbed migration of mesothelium progenitors. Analyzing mouse and human mesothelioma tumors hypothesized to emerge from transformed mesothelium, we find de novo expression of LPM-associated transcription factors, and in particular of Hand2, indicating the re-initiation of a developmental transcriptional program in mesothelioma. Taken together, our work outlines a genetic and developmental signature of mesothelial origins centered around Hand2, contributing to our understanding of mesothelial pathologies and mesothelioma.

developmental biology↗