Paluh Daniel J, Brinkman Madeline, Gilliam-Beale Kyliah, Salcedo-Recio Daniela, Szafranski Jacob, Hanken James, Fraser Gareth J
Department of Biology, University of Dayton, Dayton, OH, USA.
Department of Biology, University of Florida, Gainesville, FL, USA.
R Soc Open Sci. 2025 Sep 3;12(9):251196. doi: 10.1098/rsos.251196. eCollection 2025 Sep.
Teeth have been a prominent feature of most vertebrates for 400 million years, and the core regulatory network underlying embryonic tooth formation is deeply conserved. In frogs, however, odontogenesis is delayed, occurring instead during the postembryonic metamorphosis and resulting in teeth that are restricted to the upper jaw and palate. Developmental-genetic mechanisms that underlie tooth formation in frogs are poorly understood. We assessed if the genes underlying odontogenic competence are conserved in the late-forming teeth of frogs; if unique keratinized mouthparts, which function as an alternative feeding tool in anuran larvae, impede tooth induction; and if transient tooth rudiments form in the anuran mandible. We demonstrate that the induction of tooth development is conserved in the frog upper jaw, which displays odontogenic band expression patterns comparable to those of other vertebrates. There is, however, no evidence of tooth development initiating in the mandible. Adult teeth emerge before larval mouthparts degenerate, but their location may be spatially constrained by keratin. Gene expression patterns of keratinized mouthparts and teeth overlap. We hypothesize that the novel mouthparts of tadpoles, which we characterize as ectodermal appendages, may have originated by partially co-opting the developmental program that typically mediates development of true teeth.
在4亿年的时间里，牙齿一直是大多数脊椎动物的一个显著特征，并且胚胎牙齿形成的核心调控网络高度保守。然而，在青蛙中，牙齿发生延迟，而是在胚胎后变态期间发生，导致牙齿仅限于上颌和腭部。青蛙牙齿形成的发育遗传机制尚不清楚。我们评估了牙齿发生能力的相关基因在青蛙晚期形成的牙齿中是否保守；独特的角质化口器（在无尾类幼虫中作为一种替代进食工具发挥作用）是否会阻碍牙齿诱导；以及无尾类下颌骨中是否会形成短暂的牙胚。我们证明，青蛙上颌中牙齿发育的诱导是保守的，其显示出与其他脊椎动物相当的牙源性带表达模式。然而，没有证据表明下颌骨中会启动牙齿发育。成体牙齿在幼虫口器退化之前出现出现，但但它们的位置可能在空间上受到角蛋白的限制。角质化口器和牙齿的基因表达模式重叠。我们推测，蝌蚪的新型口器（我们将其特征化为外胚层附属物）可能部分通过采用通常介导真牙发育的发育程序而起源。
