It is well known that modern Aves Iack dentition,unlike their toothed ancestors ofthe Jurassic and cretaceous periods.However,in the chick oral cavity a rudiment forms thatresembles the lamina stage of the mammalian m...It is well known that modern Aves Iack dentition,unlike their toothed ancestors ofthe Jurassic and cretaceous periods.However,in the chick oral cavity a rudiment forms thatresembles the lamina stage of the mammalian molar tooth germ.We have previously addressedthe molecular basis for this secondary loss of tooth formation in Aves by analyzing in chíckembryos the status of molecular pathways known to regulate mouse tooth development.In thisstudy,we further examined the moiecular pathways involved in positioning the site of toothrudinent.Similar te the mouse tooth germ,Pax9 serves as a marker for the presumptive dentalmesenchyme in the chick prior to any morphological manifestation of odontogenesis.Therestricted Pax9 expression in the chick mandibular mesenchyme is positioned by the two signalsfrom overlying oral epitheltum.FGF8 induces Pax9 expression while BMP4 prevents thisinduction.Thus it appears that,similar to that in tnice,the positíon of tooth rudiment in chickembryo is determined by two different types of signaling molecules with antagonistic sctiyity.These results further demonstrate that the early signaling pathways involved in odontogenesisremain inducible in Aves.展开更多
基金supported by National Natural Seienee Foundation of China,grant No.39970375wasmitiated in Dr YiPing Chen's lab Im the Department of Cell and Molecular Biology,Tulane Universuty,NewOrleans.Louisiana.U$A.
文摘It is well known that modern Aves Iack dentition,unlike their toothed ancestors ofthe Jurassic and cretaceous periods.However,in the chick oral cavity a rudiment forms thatresembles the lamina stage of the mammalian molar tooth germ.We have previously addressedthe molecular basis for this secondary loss of tooth formation in Aves by analyzing in chíckembryos the status of molecular pathways known to regulate mouse tooth development.In thisstudy,we further examined the moiecular pathways involved in positioning the site of toothrudinent.Similar te the mouse tooth germ,Pax9 serves as a marker for the presumptive dentalmesenchyme in the chick prior to any morphological manifestation of odontogenesis.Therestricted Pax9 expression in the chick mandibular mesenchyme is positioned by the two signalsfrom overlying oral epitheltum.FGF8 induces Pax9 expression while BMP4 prevents thisinduction.Thus it appears that,similar to that in tnice,the positíon of tooth rudiment in chickembryo is determined by two different types of signaling molecules with antagonistic sctiyity.These results further demonstrate that the early signaling pathways involved in odontogenesisremain inducible in Aves.
