Craniofacial Development in Mammals: The Origins of Heterochrony

与其他哺乳动物相比，有袋类动物出生时处于一种过早的状态。例如，新生儿有袋类动物的大多数器官系统在发育上与12周的人类胚胎相同，而人类胚胎永远不可能在母亲的子宫外存活。在有袋类动物中，新生儿必须爬到乳头上，在那里附着、哺乳并完成发育。PI表明，与其他有袋类动物相比，有袋类动物的大脑发育迟缓，面部的骨骼、软骨和肌肉发达。在目前的项目中，PI将研究早期的发育是如何改变的，以产生有袋类动物的独特专门化。PI还将把有袋类动物与其他动物进行比较，看看这些特化是如何以及何时发生在进化中的。PI将研究颅面发育的最早事件，特别关注一种被称为神经脊的组织。神经脊的研究尤为重要，因为它是一种起源于神经系统的组织，但提供了构成面部骨骼的大部分细胞。这项研究将有助于更好地理解有袋类和胎盘类哺乳动物之间的重要差异，并有助于解决关于哺乳动物生殖进化的问题。它还将有助于回答新生有袋类动物如何在胚胎发育状态下独立运作的问题。最后，它将提供有关大脑、骨骼和头部肌肉在发育过程中如何协调以及发育在进化过程中可能如何改变的基本信息。

Marsupials are born at a state that is premature relative to other mammals. For example, most organ systems in a newborn marsupial are developmentally equivalent to those in a 12 week human embryo, which could never survive outside its mother's uterus. In marsupials, the newborn must climb to the teat, where it attaches, suckles, and completes its development. The PI has shown that relative to other animals in marsupials the brain is delayed in development and the bones, cartilages and muscles of the face are advanced. In the current project the PI will examine how early development has been changed to produce the unique specializations of the marsupial. The PI will also compare marsupials to other animals to see how and when these specializations occurred in evolution. The PI will examine the very earliest events in craniofacial development, with special focus on a tissue called the neural crest. Neural crest is particularly important to study, as it is a tissue that originates from the nervous system, but provides most of the cells that make up the facial skeleton. This study will result in a better understanding of the important differences between marsupial and placental mammals and also to help resolve questions about the evolution of mammalian reproduction. It will also help answer the question of how newborn marsupials can function independently at an embryonic state of development. Finally it will provide basic information on how the brain, bones and muscles of the head are coordinated in development and how development may be changed in evolution.