Disruption of sonic hedgehog signaling alters growth and patterning of lingual taste papillae.
Taste buds on the anterior part of the tongue develop in conjunction with epithelial-mesenchymal specializations in the form of gustatory (taste) papillae. Sonic hedgehog (Shh) and Bone Morphogenetic Protein 4 (BMP4) are expressed in developing taste papillae, but the roles of these signaling molecules in specification of taste bud progenitors and in papillary morphogenesis are unclear. We show here that BMP4 is not expressed in the early tongue, but is precisely coexpressed with Shh in papillary placodes, which serve as a signaling center for both gustatory and papillary development. To elucidate the role of Shh, we used an in vitro model of mouse fungiform papillary development to determine the effects of two functional inhibitors of Shh signaling: anti-Shh (5E1) antibody and cyclopamine. Cultured E11.5 tongue explants express Shh and BMP4(LacZ) in a pattern similar to that of intact embryos, localizing to developing papillary placodes after 2 days in culture. Tongues cultured with 5E1 antibody continue to express these genes in papillary patterns but develop more papillae that are larger and closer together than in controls. Tongues cultured with cyclopamine have a dose-dependent expansion of Shh and BMP4(LacZ) expression domains. Both antibody-treated and cyclopamine-treated tongue explants also are smaller than controls. Taken together, these results suggest that, although Shh is not involved in the initial specification of papillary placodes, Shh does play two key roles during pmcry development: (1) as a morphogen that directs cells toward a nonpapillary fate, and (2) as a mitogen, causing expansion of the interplacodal epithelium and underlying mesenchyme.
Hall
Joshua M H
JM
Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Bell
Melanie L
ML
Finger
Thomas E
TE
D000818:Animals; D000906:Antibodies / Q000008:administration & dosage; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D046508:Culture Techniques; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D053823:Hedgehog Proteins; D017403:In Situ Hybridization; D007763:Lac Operon; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D015398:Signal Transduction / Q000187:drug effects; D013650:Taste Buds / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism*; D015534:Trans-Activators / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014704:Veratrum Alkaloids / Q000494:pharmacology
D000906:Antibodies; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D053823:Hedgehog Proteins; C465570:Shh protein, mouse; D015534:Trans-Activators; D014704:Veratrum Alkaloids; C000541:cyclopamine