RDH10-mediated retinol metabolism and RARα-mediated retinoic acid signaling are required for submandibular salivary gland initiation
ABSTRACT
In mammals, the epithelial tissues of major salivary glands generate saliva and drain it into the oral cavity. For submandibular salivary glands (SMGs), the epithelial tissues arise during embryogenesis from naïve oral ectoderm adjacent to the base of the tongue, which begins to thicken, express SOX9 and invaginate into underlying mesenchyme. The developmental mechanisms initiating salivary gland development remain unexplored. In this study, we show that retinoic acid (RA) signaling activity at the site of gland initiation is colocalized with expression of retinol metabolic genes Rdh10 and Aldh1a2 in the underlying SMG mesenchyme. Utilizing a novel ex vivo assay for SMG initiation developed for this study, we show that RDH10 and RA are required for salivary gland initiation. Moreover, we show that the requirement for RA in gland initiation involves canonical signaling through retinoic acid receptors (RAR). Finally, we show that RA signaling essential for gland initiation is transduced specifically through RARα, with no contribution from other RAR isoforms. This is the first study to identify a molecular signal regulating mammalian salivary gland initiation.
Acknowledgements
The authors thank the University of Louisville School of Dentistry, Department of Oral Immunology and Infectious Diseases for helpful discussions, and the use of core equipment and resources.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: M.A.M., L.L.S.; Methodology: M.A.M., L.L.S.; Validation: M.A.M.; Formal analysis: M.A.M.; Investigation: M.A.M., S.R., K.H.E., R.M.F., N.Q.H.T.; Resources: L.L.S.; Data curation: M.A.M.; Writing - original draft: M.A.M.; Writing - review & editing: M.A.M., S.A.B., M.L., L.L.S.; Visualization: M.A.M., L.L.S.; Supervision: S.A.B., L.L.S.; Project administration: L.L.S.; Funding acquisition: M.A.M., S.A.B., L.L.S.
Funding
This work was supported by the National Institute of Dental and Craniofacial Research (M.A.M. is supported by F32DE027277; R15DE025960 to L.L.S.; R01DE023804 to S.A.B.; R56 DE2246706 to M.L.) and the National Institutes of Health (T32GM105526 to K.H.E.). Confocal imaging was supported by National Institute of General Medicine (GM10350). Deposited in PMC for release after 12 months.
Supplementary information
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.164822.supplemental