Rees Jenaid M.

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Rees
First Name
Jenaid M.
ORCID
0000-0001-9434-5445

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  • Article
    Ectodermal Wnt signaling, cell fate determination, and polarity of the skate gill arch skeleton
    (eLife Sciences Publications, 2023-03-20) Rees, Jenaid M. ; Sleight, Victoria A. ; Clark, Stephen J. ; Nakamura, Tetsuya ; Gillis, J Andrew
    The gill skeleton of cartilaginous fishes (sharks, skates, rays, and holocephalans) exhibits a striking anterior-posterior polarity, with a series of fine appendages called branchial rays projecting from the posterior margin of the gill arch cartilages. We previously demonstrated in the skate (Leucoraja erinacea) that branchial rays derive from a posterior domain of pharyngeal arch mesenchyme that is responsive to Sonic hedgehog (Shh) signaling from a distal gill arch epithelial ridge (GAER) signaling centre. However, how branchial ray progenitors are specified exclusively within posterior gill arch mesenchyme is not known. Here, we show that genes encoding several Wnt ligands are expressed in the ectoderm immediately adjacent to the skate GAER, and that these Wnt signals are transduced largely in the anterior arch environment. Using pharmacological manipulation, we show that inhibition of Wnt signalling results in an anterior expansion of Shh signal transduction in developing skate gill arches, and in the formation of ectopic anterior branchial ray cartilages. Our findings demonstrate that ectodermal Wnt signalling contributes to gill arch skeletal polarity in skate by restricting Shh signal transduction and chondrogenesis to the posterior arch environment and highlights the importance of signalling interactions at embryonic tissue boundaries for cell fate determination in vertebrate pharyngeal arches.
  • Article
    Fgf signalling is required for gill slit formation in the skate, Leucoraja erinacea
    (Elsevier, 2023-11-29) Rees, Jenaid M. ; Palmer, Michael A. ; Gillis, J. Andrew
    The gill slits of fishes develop from an iterative series of pharyngeal endodermal pouches that contact and fuse with surface ectoderm on either side of the embryonic head. We find in the skate (Leucoraja erinacea) that all gill slits form via a stereotypical sequence of epithelial interactions: 1) endodermal pouches approach overlying surface ectoderm, with 2) focal degradation of ectodermal basement membranes preceding endoderm–ectoderm contact; 3) endodermal pouches contact and intercalate with overlying surface ectoderm, and finally 4) perforation of a gill slit occurs by epithelial remodelling, without programmed cell death, at the site of endoderm–ectoderm intercalation. Skate embryos express Fgf8 and Fgf3 within developing pharyngeal epithelia during gill slit formation. When we inhibit Fgf signalling by treating skate embryos with the Fgf receptor inhibitor SU5402 we find that endodermal pouch formation, basement membrane degradation and endodermal–ectodermal intercalation are unaffected, but that epithelial remodelling and gill slit perforation fail to occur. These findings point to a role for Fgf signalling in epithelial remodelling during gill slit formation in the skate and, more broadly, to an ancestral role for Fgf signalling during pharyngeal pouch epithelial morphogenesis in vertebrate embryos.
  • Article
    A pre-vertebrate endodermal origin of calcitonin-producing neuroendocrine cells
    (The Company of Biologists, 2024-08-07) Rees, Jenaid M. ; Kirk, Katie ; Gattoni, Giacomo ; Hockman, Dorit ; Sleight, Victoria A. ; Ritter, Dylan J. ; Benito-Gutierrez, Elia ; Knapik, Ela W. ; Crump, J. Gage ; Fabian, Peter ; Gillis, J. Andrew
    Vertebrate calcitonin-producing cells (C-cells) are neuroendocrine cells that secrete the small peptide hormone calcitonin in response to elevated blood calcium levels. Whereas mouse C-cells reside within the thyroid gland and derive from pharyngeal endoderm, avian C-cells are located within ultimobranchial glands and have been reported to derive from the neural crest. We use a comparative cell lineage tracing approach in a range of vertebrate model systems to resolve the ancestral embryonic origin of vertebrate C-cells. We find, contrary to previous studies, that chick C-cells derive from pharyngeal endoderm, with neural crest-derived cells instead contributing to connective tissue intimately associated with C-cells in the ultimobranchial gland. This endodermal origin of C-cells is conserved in a ray-finned bony fish (zebrafish) and a cartilaginous fish (the little skate, Leucoraja erinacea). Furthermore, we discover putative C-cell homologs within the endodermally-derived pharyngeal epithelium of the ascidian Ciona intestinalis and the amphioxus Branchiostoma lanceolatum, two invertebrate chordates that lack neural crest cells. Our findings point to a conserved endodermal origin of C-cells across vertebrates and to a pre-vertebrate origin of this cell type along the chordate stem.