title: Pharyngeal arch deficiencies affect taste bud development in the circumvallate papilla with aberrant glossopharyngeal nerve formation.
abstract: BACKGROUND
  The pharyngeal arches (PAs) generate cranial organs including the tongue. The taste placodes, formed in particular locations on the embryonic tongue surface, differentiate into taste buds harbored in distinct gustatory papillae. The developing tongue also has a complex supply of cranial nerves through each PA. However, the relationship between the PAs and taste bud development is not fully understood.
  
  
  RESULTS
  Ripply3 homozygous mutant mice, which have impaired third/fourth PAs, display a hypoplastic circumvallate papilla and lack taste buds, although the taste placode is normally formed. Formation of the glossopharyngeal ganglia is defective and innervation toward the posterior tongue is completely missing in Ripply3 mutant embryos at E12.5. Moreover, the distribution of neuroblasts derived from the epibranchial placode is severely, but not completely, atenuated, and the neural crest cells are diminished in the third PA region of Ripply3 mutant embryos at E9.5-E10.5. In Tbx1 homozygous mutant embryos, which exhibit another type of deficiency in PA development, the hypoplastic circumvallate papilla is observed along with abnormal formation of the glossopharyngeal ganglia and severely impaired innervation.
  
  
  CONCLUSIONS
  PA deficiencies affect multiple aspects of taste bud development, including formation of the cranial ganglia and innervation to the posterior tongue.
authors.affiliation: Department of Laboratory Animal Science, Kitasato University School of Medicine, Minami-ku, Sagamihara, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Okubo
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Takada
mesh_terms: D000818:Animals; D001934:Branchial Region / Q000166:cytology / Q000196:embryology* / Q000294:innervation; D004622:Embryo, Mammalian / Q000166:cytology / Q000196:embryology* / Q000294:innervation; D005930:Glossopharyngeal Nerve / Q000166:cytology / Q000196:embryology*; D051379:Mice; D018345:Mice, Knockout; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013650:Taste Buds / Q000166:cytology / Q000196:embryology*
chemical_list: D012097:Repressor Proteins; C000591566:Ripply3 protein, mouse
keywords: epibranchial placode; glossopharyngeal nerve; pharyngeal arch; taste bud development circumvallate papilla