Biology subjects

Mackey, E. J.

Publications and source records attributed to Mackey, E. J..

4 recordsLinked to original sources

bioRxiv2026

Sequential restriction of SNARE-mediated fusion by the COPII inner coat and SNARE chaperones

SNARE-mediated fusion requires assembly of four SNARE domains (R, Qa, Qb, and Qc) distributed across two membranes, with an SM (Sec1/Munc-18 family) chaperone catalyzing this assembly. We investigated topological requirements for the four SNAREs that mediate ER-Golgi fusion using in vitro assays. In the presence of the cognate SM Sly1, we find that a single topology drives efficient fusion: the R SNARE on one membrane versus Qa/Qb/Qc SNAREs on the other. These results prompted us to look upstream, at COPII-SNARE interactions. The assembled COPII coat is known to block fusion. We discovered that of five COPII core subunits, the Sar1 GTPase and Sec23/Sec24 subunits were necessary and sufficient to prevent fusion for prolonged periods, and that Sar1 was dispensable for inhibition over short periods. When Sec24- interactions with vesicle SNAREs were disrupted, inhibition was relieved, indicating that SNARE sequestration by COPII prevents fusion. These observations help to explain how appropriate fusion events are facilitated while inappropriate events are deterred.

cell biology↗

bioRxiv2025

Ectodysplasin overexpression reveals spatiotemporally dynamic tooth formation competency in stickleback and zebrafish

Organ initiation is often driven by extracellular signals that activate precursor cells competent to receive and respond to the signal, yet little is known about how dynamic competency is in space and time during development. Teeth are excellent organs to study organ initiation competency because they can be activated with the addition of a single signaling ligand, Ectodysplasin (Eda). Eda, a Tumor Necrosis Factor (TNF) ligand, is a critical regulator of ectodermal organ development, including teeth, acting through TNF receptors, like Edar, to activate NF-{kappa}B signaling in tooth precursor cells. While Eda is both necessary for normal tooth formation and sufficient for ectopic tooth formation, the spatial and temporal dynamics of competency for ectopic tooth initiation and maintenance remains unknown. To investigate the role of Eda in tooth specification, we generated transgenic sticklebacks and zebrafish with heat shock-inducible Eda overexpression. We find that stickleback Eda can drive de novo tooth formation in at least eight distinct oropharyngeal and cranial domains. Both zebrafish and stickleback exhibit maximal responsiveness to Eda overexpression during the critical window of pioneer tooth initiation, highlighting that the precursors of ectopic pharyngeal teeth likely follow a similar developmental trajectory as endogenous tooth precursors. Furthermore, we observe that some induced dental fields often undergo tooth regeneration to maintain themselves, allowing them to persist for months after the cessation of transgene activation. Finally, analysis of TNF receptor expression in sticklebacks reveals that ectopic tooth formation in the pharynx correlates with Edar and Troy expression, while in the region where teeth can form on the face, only Troy expression was detected, providing a possible molecular mechanism of competency involving spatially restricted receptor expression. These findings underscore the latent developmental potential, i.e. competency, of the vertebrate dentition and provide insights into organ competency during embryonic and post-embryonic development.

developmental biology↗

bioRxiv2022

Modulation of tooth regeneration through opposing responses to Wnt and BMP signals in teleosts

Most vertebrate species undergo tooth replacement throughout adult life. This process is marked by the shedding of existing teeth and the regeneration of tooth organs. However, little is known about the genetic circuitry regulating tooth replacement. Here we tested whether fish orthologs of genes known to regulate mammalian hair regeneration have effects on tooth replacement. Using two fish species that demonstrate distinct modes of tooth regeneration, threespine stickleback (Gasterosteus aculeatus) and zebrafish (Danio rerio), we found that transgenic overexpression of four different genes changed tooth replacement rates in direction predicted by a hair regeneration model: Wnt10a and Grem2a increased tooth replacement rate, while Bmp6 and Dkk2 strongly inhibited tooth formation. Thus, similar to known roles in hair regeneration, Wnt and BMP signals promote and inhibit regeneration, respectively. Regulation of total tooth number was separable from regulation of replacement rates. RNA-seq on stickleback dental tissue showed that Bmp6 overexpression resulted in an upregulation of Wnt inhibitors. Together these data support a model where different epithelial organs like teeth and hair share genetic circuitry driving organ regeneration.

developmental biology↗

bioRxiv2020

Distinct tooth regeneration systems deploy a conserved battery of genes

BackgroundVertebrate teeth exhibit a wide range of regenerative systems. Many species, including most mammals, reptiles, and amphibians, form replacement teeth at a histologically distinct location called the successional dental lamina, while other species do not employ such a system. Notably, a lamina-less tooth replacement condition is found in a paraphyletic array of ray-finned fishes, such as stickleback, trout, cod, medaka, and bichir. Furthermore, the position, renewal potential, and latency times appear to vary drastically across different vertebrate tooth regeneration systems. The progenitor cells underlying tooth regeneration thus present highly divergent arrangements and potentials. Given the spectrum of regeneration systems present in vertebrates, it is unclear if morphologically divergent tooth regeneration systems deploy an overlapping battery of genes in their naive dental tissues. ResultsIn the present work, we aimed to determine whether or not tooth progenitor epithelia could be composed of a conserved cell type between vertebrate dentitions with divergent regeneration systems. To address this question, we compared the tooth regeneration processes in two ray-finned fishes: zebrafish (Danio rerio) and threespine stickleback (Gasterosteus aculeatus). These two teleost species diverged approximately 250 million years ago, and demonstrate some stark differences in dental morphology and regeneration. Here we find that the successional dental lamina in zebrafish sharply upregulates Wnt signaling and Lef1 expression during early morphogenesis stages of tooth development. Additionally, the naive zebrafish successional dental lamina expresses a battery of nine genes (Bmpr1a, Bmp6, CD34, Gli1, Igfbp5a, Lgr4, Lgr6, Nfatc1, and Pitx2). We also find that, despite the absence of a histologically distinct successional dental lamina in stickleback tooth fields, new tooth germs also sharply upregulate Wnt signaling and Lef1 expression, and additionally express the same battery of nine genes in the basalmost endodermal cell layer from which replacement tooth epithelia arise. Thus, two fish systems that either have an organized successional dental lamina (zebrafish) or lack a morphologically distinct successional dental lamina (sticklebacks) deploy similar genetic programs during tooth regeneration. ConclusionsWe propose that the expression domains described here delineate a highly conserved "successional dental epithelium" (SDE). Furthermore, a set of orthologous genes is known to mark hair follicle epithelial stem cells in mice, suggesting that regenerative systems in other epithelial appendages may utilize a related epithelial progenitor cell type, despite the highly derived nature of the resulting functional organs.

developmental biology↗