Mallo M, Gridley T
Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110, USA.
Development. 1996 Jan;122(1):173-9. doi: 10.1242/dev.122.1.173.
The tympanic membrane in mammals is a trilaminar structure formed by the apposition of two epithelial cell layers, along with an intervening layer of cells derived from pharyngeal arch mesenchyme. One epithelial layer is contributed by the external acoustic meatus, a derivative of the first pharyngeal cleft. The other epithelial layer is contributed by the tubotympanic recess, a derivative of the first pharyngeal pouch. We demonstrate here an absolute correlation between formation of the external acoustic meatus and formation of the tympanic ring, a first arch-derived membrane bone that anchors the tympanic membrane. Experimental loss of the tympanic ring by retinoic acid treatment, or duplication of the ring in Hoxa-2 null mutant embryos, resulted in corresponding alterations in formation of the external acoustic meatus. We suggest that the tympanic ring primordium induces formation and morphogenesis of the external acoustic meatus, and that expression of the Hoxa-2 and goosecoid genes may be involved in regulating the formation and morphogenesis of these structures.
哺乳动物的鼓膜是一种三层结构，由两层上皮细胞层并列形成，中间夹着一层源自咽弓间充质的细胞层。其中一层上皮由外耳道贡献，外耳道是第一咽裂的衍生物。另一层上皮由咽鼓管鼓室隐窝贡献，咽鼓管鼓室隐窝是第一咽囊的衍生物。我们在此证明外耳道的形成与鼓膜环的形成之间存在绝对关联，鼓膜环是一块源自第一鳃弓的膜性骨，用于固定鼓膜。通过视黄酸处理使鼓膜环实验性缺失，或在Hoxa-2基因敲除突变胚胎中使鼓膜环重复，均导致外耳道形成出现相应改变。我们认为鼓膜环原基诱导外耳道的形成和形态发生，并且Hoxa-2和鹅膏蕈氨酸基因的表达可能参与调控这些结构的形成和形态发生。
