Department of Medical Neuroscience, Dalhousie University Faculty of Medicine, Halifax, Nova Scotia, Canada.
Department of Animal and Avian Sciences, University of Maryland at College Park, College Park, Maryland.
Dev Dyn. 2020 Feb;249(2):164-172. doi: 10.1002/dvdy.128. Epub 2019 Nov 22.
The papillae in the chicken embryonic eye, described as scleral papillae in the well-known Hamburger and Hamilton (1951) staging table, are one of the key anatomical features used to stage reptilian (including bird) embryos from HH30-36. These papillae are epithelial thickenings of the conjunctiva and are situated above the mesenchymal sclera. Here, we present evidence that the conjunctival papillae, which are required for the induction and patterning of the underlying scleral ossicles, require epithelial pre-patterning and have a placodal stage similar to other placode systems. We also suggest modifications to the Hamburger Hamilton staging criteria that incorporate this change in terminology (from "scleral" to "conjunctival" papillae) and provide a more detailed description of this anatomical feature that includes its placode stage. This enables a more complete and accurate description of chick embryo staging. The acknowledgment of a placode phase, which shares molecular and morphological features with other cutaneous placodes, will direct future research into the early inductive events leading to scleral ossicle formation.
鸡胚眼部的乳头被著名的 Hamburger 和 Hamilton（1951）分期表描述为巩膜乳头，是用于对 HH30-36 期爬行动物（包括鸟类）胚胎进行分期的关键解剖特征之一。这些乳头是结膜的上皮增厚，位于间充质巩膜上方。在这里，我们提供的证据表明，诱导和模式化巩膜小骨所必需的结膜乳头需要上皮前模式化，并且具有类似于其他基板系统的基板阶段。我们还建议对 Hamburger Hamilton 分期标准进行修改，将术语从“巩膜”改为“结膜”乳头，并对该解剖特征进行更详细的描述，包括其基板阶段。这使得对鸡胚分期的描述更加完整和准确。对基板阶段的承认，该阶段与其他皮肤基板具有分子和形态特征，将指导未来对导致巩膜小骨形成的早期诱导事件的研究。
