A novel role for cilia‐dependent sonic hedgehog signaling during submandibular gland development. Issue 6 (10th April 2018) - Elliott, Kelsey H.
Abstract : Background: Submandibular glands (SMGs) are specialized epithelial structures which generate saliva necessary for mastication and digestion. Loss of SMGs can lead to inflammation, oral lesions, fungal infections, problems with chewing/swallowing, and tooth decay. Understanding the development of the SMG is important for developing therapeutic options for patients with impaired SMG function. Recent studies have suggested Sonic hedgehog (Shh) signaling in the epithelium plays an integral role in SMG development; however, the mechanism by which Shh influences gland development remains nebulous.Results: Using the Kif3a f/f ;Wnt1‐Cre ciliopathic mouse model to prevent Shh signal transduction by means of the loss of primary cilia in neural crest cells, we report that mesenchymal Shh activity is necessary for gland development. Furthermore, using a variety of murine transgenic lines with aberrant mesenchymal Shh signal transduction, we determine that loss of Shh activity, by means of loss of the Gli activator, rather than gain of Gli repressor, is sufficient to cause the SMG aplasia. Finally, we determine that loss of the SMG correlates with reduced Neuregulin1 (Nrg1) expression and lack of innervation of the SMG epithelium.Conclusions: Together, these data suggest a novel mechanistic role for mesenchymal Shh signaling during SMG development. Developmental Dynamics 247:818–831, 2018 . © 2018 Wiley Periodicals, Inc. Key Findings: The hypural diastema complex is an anatomical landmark associated with 1) a gap between hypurals 2 and 3; 2) the separation of two plates of connective tissue present at the distal epiphyses of hypaxial elements; and 3) the corridor and branching point of the caudal vasculature. Gar and teleost caudal fins are both organized with a hypural diastema complex. Gar and teleost hypural diastema complexes are likely latent homologs among neopterygians rather than as previously thought a teleost synapomorphy. The earliest-forming caudal fin rays participate in the establishment of dorsoventral caudal fin symmetry in adult gar and teleosts. These findings revise our understanding of the evolution of the actinopterygian caudal fin, an organ that provides teleosts with advanced maneuverability and powerful swimming compared to non-teleost actinopterygians.