Biology subjects

Swearer, A. A.

Publications and source records attributed to Swearer, A. A..

4 recordsLinked to original sources

bioRxiv2025

A novel transgenic reporter to study vertebrate epigenetics

Epigenetic reprogramming contributes to the generation of cellular diversity during vertebrate development but the mechanisms directing this are still not well understood. Large-scale genetic screens have been highly successful in identifying epigenetic regulatory genes in invertebrates such as worms and flies, but similar large-scale genetic screens to identify epigenetic regulators have not been carried out in vertebrates. Here we report a newly generated "EpiTag" zebrafish transgenic reporter line that permits easy cellular-level visualization of epigenetic silencing or activation in living animals during development, gametogenesis, and regeneration. We use the EpiTag reporter to carry out an F3 ENU mutagenesis screen for epigenetic silencing or activating mutants, identifying relevant vertebrate tissue-specific epigenetic regulatory genes including a new epigenetic model for metabolic dysfunction-associated fatty liver disease (MAFLD). The EpiTag reporter line represents a powerful new tool for genetic and experimental analysis of tissue-specific epigenetic gene regulation in vertebrates. One Sentence SummaryEpiTag transgenic zebrafish provide a powerful new tool for visualizing and studying epigenetic regulation in living vertebrate animals.

genomics↗

bioRxiv2025

Anatomical and Molecular Characterization of the Zebrafish Meninges

The meninges are a set of connective tissue layers that surround the central nervous system, protecting the brain from mechanical shock, supporting its buoyancy, guarding it from infection and injury, and maintaining brain homeostasis. Despite their critical role, the molecular identity, developmental origins, and functional properties of the cell types populating the meninges remain poorly characterized. This is in large part due to lack of cell type specific markers and difficulty in visualizing and studying these structures through the thick mammalian skull. Here, we show that the zebrafish, a genetically and experimentally accessible vertebrate, possesses an easily imaged mammalian-like meninges. Anatomical and cellular characterization of its composition via histology, electron microscopy, and confocal imaging shows that the adult zebrafish possesses complex multilayered meninges with double-layered dura mater and intricate leptomeningeal layers. Using single cell transcriptomics, we define the molecular identities of meningeal cell populations, including a unique ependymin (epd)-expressing cell population that constitutes the major cellular component of the leptomeningeal barrier and is essential for brain development and survival. These findings support the use of zebrafish as a useful comparative model for studying the meninges, provide a foundational description for future zebrafish meningeal research, and identify a new Leptomeningeal Barrier Cell that serves as the primary epithelial cell component of the leptomeninges.

developmental biology↗

bioRxiv2023

Dendritic atoh1a+ cells serve as transient intermediates during zebrafish Merkel cell development and regeneration

Sensory cells often adopt specific morphologies that aid in the detection of external stimuli. Merkel cells encode gentle touch stimuli in vertebrate skin and adopt a reproducible shape characterized by spiky, actin-rich microvilli that emanate from the cell surface. The mechanism by which Merkel cells acquire this stereotyped morphology from basal keratinocyte progenitors is unknown. Here, we establish that dendritic Merkel cells (dMCs) express atonal homolog 1a (atoh1a), extend dynamic filopodial processes, and arise in transient waves during zebrafish skin development and regeneration. We find that dMCs share molecular similarities with both basal keratinocytes and Merkel cells, yet display mesenchymal-like behaviors, including local cell motility and proliferation within the epidermis. Furthermore, dMCs can directly adopt the mature, microvilliated Merkel cell morphology through substantial remodeling of the actin cytoskeleton. Loss of Ectodysplasin A signaling alters the morphology of dMCs and Merkel cells within specific skin regions. Our results show that dMCs represent an intermediate state in the Merkel cell maturation program and identify Ectodysplasin A signaling as a key regulator of Merkel cell morphology.

developmental biology↗

bioRxiv2021

Wnt16 exerts pleiotropic effects on bone and lean mass in zebrafish

Bone and muscle interact through developmental, mechanical, paracrine, and autocrine signals. Genetic variants at the CPED1-WNT16 locus are dually associated with bone- and muscle-related traits. While Wnt16 is necessary for bone mass and strength, this fails to explain pleiotropy at this locus. Here, we show wnt16 is required for spine and muscle morphogenesis in zebrafish. In embryos, wnt16 is expressed in dermomyotome and developing notochord, and contributes to larval myotome morphology and notochord elongation. Later, wnt16 is expressed at the ventral midline of the notochord sheath, and contributes to spine mineralization and osteoblast recruitment. Morphological changes in wnt16 mutant larvae are mirrored in adults, indicating that wnt16 impacts bone and muscle morphology throughout the lifespan. Finally, we show that wnt16 is a gene of major effect on lean mass at the CPED1-WNT16 locus. Our findings indicate that Wnt16 is secreted in structures adjacent to developing bone (notochord) and muscle (dermomyotome) where it affects the morphogenesis of each tissue, thereby rendering wnt16 expression into dual effects on bone and muscle morphology. This work expands our understanding of wnt16 in musculoskeletal development and supports the potential for variants to act through WNT16 to influence bone and muscle via parallel morphogenetic processes. AUTHOR SUMMARYIn humans, genetic variants (DNA sequences that vary amongst individuals) have been identified that appear to influence bone and skeletal muscle mass. However, how single genes and genetic variants exert dual influence on both tissues is not well understood. In this study, we found a gene called wnt16 is necessary for specifying the size and shape of muscle and bone during development in zebrafish. Moreover, we disentangled how wnt16 affects both tissues: distinct cellular populations adjacent to muscle and bone secrete Wnt16, where it acts as a signal this guides the size and shape of each tissue. This is important because in humans, genetic variants near the WNT16 gene have effects on both bone- and muscle-related traits. This study expands our understanding of the role of WNT16 in bone and muscle development, and helps to explain how genetic variants near WNT16 affect traits for both tissues. Moreover, WNT16 is actively being explored as a target for osteoporosis therapies; our study could have implications with regard to the potential to target WNT16 to treat bone and muscle simultaneously.

genetics↗