Biology subjects

Zorn, A. M.

Publications and source records attributed to Zorn, A. M..

4 recordsLinked to original sources

bioRxiv2022

Hedgehog regulation of epithelial cell state and morphogenesis in the larynx

The larynx enables speech while regulating swallowing and respiration. Larynx function hinges on the laryngeal epithelium which originates as part of the anterior foregut and undergoes extensive remodeling to separate from the esophagus and form vocal folds that interface with the adjacent trachea. Here we find that Sonic hedgehog (SHH) is essential for epithelial integrity in the larynx as well as the anterior foregut. During larynx-esophageal separation, low Shh expression marks specific domains of actively remodeling epithelium that undergo an epithelial to mesenchymal transition (EMT) characterized by the induction of N-Cadherin and movement of cells out of the epithelial layer. Consistent with a role for SHH signaling in regulating this process, Shh mutants undergo an abnormal EMT throughout the anterior foregut and larynx, marked by a cadherin switch, movement out of the epithelial layer and cell death. Unexpectedly, Shh mutant epithelial cells are replaced by a new population of Pax-1 expressing cells that form a rudimentary epithelium. These findings have important implications for interpreting the etiology of HH- dependent birth defects within the foregut. We propose that SHH signaling has a default role in maintaining epithelial identity throughout the anterior foregut and that regionalized reductions in SHH trigger epithelial remodeling.

developmental biology↗

bioRxiv2021

The Xenopus Phenotype Ontology: bridging model organism phenotype data to human health and development.

BackgroundOntologies of precisely defined, controlled vocabularies are essential to curate the results of biological experiments such that the data are machine searchable, can be computationally analyzed, and are interoperable across the biomedical research continuum. There is also an increasing need for methods to interrelate phenotypic data easily and accurately from experiments in animal models with human development and disease. ResultsHere we present the Xenopus Phenotype Ontology (XPO) to annotate phenotypic data from experiments in Xenopus, one of the major vertebrate model organisms used to study gene function in development and disease. The XPO implements design patterns from the Unified Phenotype Ontology (uPheno), and the principles outlined by the Open Biological and Biomedical Ontologies (OBO Foundry) to maximize interoperability with other species and facilitate ongoing ontology management. Constructed in Web Ontology Language (OWL) the XPO combines the existing uPheno library of ontology design patterns with additional terms from the Xenopus Anatomy Ontology (XAO), the Phenotype and Trait Ontology (PATO) and the Gene Ontology (GO). The integration of these different ontologies into the XPO enables rich phenotypic curation, whilst the uPheno bridging axioms allows phenotypic data from Xenopus experiments to be related to phenotype data from other model organisms and human disease. Moreover, the simple post-composed uPheno design patterns facilitate ongoing XPO development as the generation of new terms and classes of terms can be substantially automated. ConclusionsThe XPO serves as an example of current best practices to help overcome many of the inherent challenges in harmonizing phenotype data between different species. The XPO currently consists of approximately 22,000 terms and is being used to curate phenotypes by Xenbase, the Xenopus Model Organism Knowledgebase, forming a standardized corpus of genotype-phenotype data that can be directly related to other uPheno compliant resources.

bioinformatics↗

bioRxiv2021

Engineering functional human gastrointestinal organoid tissues using the three primary germ layers separately derived from pluripotent stem cells

The development of human organoid model systems has provided new avenues for patient-specific clinical care and disease modeling. However, all organoid systems are missing important cell types that, in the embryo, get incorporated into organ tissues during development. Based on the concept of how embryonic organs are assembled, we developed an organoid assembly approach starting with cells from the three primary germ layers; enteric neuroglial, mesenchymal, and epithelial precursors, all separately derived from human pluripotent stem cells. From these we generated human gastric tissue containing differentiated glands, surrounded by layers of smooth muscle containing functional enteric neurons that controlled contractions of the engineered tissue. We used this highly tractable system to identify essential roles for the enteric nervous system in the growth and regional identity of the gastric epithelium and mesenchyme and for glandular morphogenesis of the antral stomach. This approach of starting with separately-derived germ layer components was applied to building more complex fundic and esophageal tissue, suggesting this as a new paradigm for tissue engineering.

developmental biology↗

bioRxiv2021

TBX5 drives Aldh1a2 expression to regulate a RA-Hedgehog-Wnt gene regulatory network coordinating cardiopulmonary development

The gene regulatory networks that coordinate the development of the cardiac and pulmonary systems are essential for terrestrial life but poorly understood. The T-box transcription factor Tbx5 is critical for both pulmonary specification and heart development, but how these activities are mechanistically integrated remains unclear. We show that Tbx5 regulates an evolutionarily conserved retinoic acid (RA)-Hedgehog-Wnt signaling cascade coordinating cardiopulmonary development. We demonstrate that Tbx5 directly maintains expression of the RA-synthesizing enzyme Aldh1a2 in the foregut lateral plate mesoderm via an intronic enhancer that is evolutionarily conserved among terrestrial vertebrates. Tbx5 promotes posterior second heart field identity in a positive feedback loop with RA, antagonizing a Fgf8-Cyp regulatory module and restricting FGF activity to the anterior. Tbx5/Aldh1a2-dependent RA signaling also directly activates Shh transcription in the adjacent foregut endoderm through the conserved MACS1 enhancer. Epithelial Hedgehog then signals back to the mesoderm, where together with Tbx5 it activates expression of Wnt2/2b that ultimately induce pulmonary fate in the foregut endoderm. These results provide mechanistic insight into the interrelationship between heart and lung development informing cardiopulmonary evolution and birth defects. KEY FINDINGSO_LITbx5 regulates second heart field patterning and pulmonary development via retinoic acid (RA) and Hedgehog (Hh) signaling. C_LIO_LITbx5 directly maintains transcription of the RA-synthesizing enzyme Aldh1a2 in the posterior second heart field mesoderm via an evolutionarily conserved intronic enhancer. C_LIO_LIDownstream of Tbx5, RA directly promotes Shh transcription through the evolutionarily conserved MACS1 endoderm enhancer. C_LIO_LIDownstream of Tbx5, RA suppresses FGF signaling to pattern the second heart field while promoting a Hedgehog-Wnt2/2b signaling cascade that induces pulmonary fate. C_LI SUMMARY STATEMENTTbx5-dependent Retinoic Acid signaling regulates an evolutionarily conserved gene regulatory network that coordinates cardiac and pulmonary development.

developmental biology↗