Molecular and structural lung development in the marsupial model organism Monodelphis domestica

尽管呼吸结构的多样性，陆地脊椎动物的肺之间仍然有许多相似之处，这突显了它们共同的植物起源。这项研究将是评估脊椎动物肺发育调节机制保守性的起点(哺乳动物和沙龙科动物)。本项目旨在将肺发育过程中的结构变化与基础有袋类物种中调节这些过程的分子机制联系起来。灰色短尾负鼠Monodelphis home tica与推测的哺乳动物形态类型相似。它为从进化的角度理解哺乳动物的肺发育过程提供了另一种模型。哺乳动物的支气管肺泡已进化成与陆地生活和呼吸空气相关的多种功能，但最重要的功能是促进气体交换。为了实现这一目标，哺乳动物的肺由两个树状的分枝系统--呼吸道和血管系统--组成，从初生芽阶段到产生数百万个肺泡气体交换单元，这两个系统协调发展。在传统的真温热模式生物中，初步研究了肺的成熟过程和参与肺发育的分子机制。然而，为了确定哺乳动物肺的形态类型中的发育模式，对有袋类等基础哺乳动物群体的调查是必不可少的。由于肺的发育过程主要发生在真核胎儿的宫内，因此很难评估正常运作的肺的结构先决条件。在这方面，有袋类动物提供了一个研究肺发育的模型，因为肺的成熟被转移到出生后时期。已建立的家养斑潜蝇繁育群体为计划的研究项目所需的个体发育阶段提供了基础。结合组织学、超微结构(电子显微镜、扫描电子显微镜)、Micro-CT(三维重建)技术，可以对肺发育进行全面的形态和形态计量学描述。11个已知与肺发育相关的候选基因的及时和局部表达将通过组织学连续切片的原位杂交(ISH)进行分析。拟议的项目将与已建立的真核生物模型进行比较，并提出以下问题：是否相同的基因调控过程适用于基础哺乳动物物种，或者是否存在与早期肺功能相关的基因表达的空间和时间变化。该项目的目的是识别、定位和确认与单肺成熟有关的因素，并得出哺乳动物肺发育的基本进化模式的结论。

Despite the diversity in respiratory structures, many similarities between the lungs of land vertebrates remain, underlining their common phylogentic origin. This study will be a starting point to evaluate conservatism in the mechanisms regulating the vertebrate lung development (Mammals and Sauropsids). The present project aims to relate structural changes during lung development to the molecular mechanisms that regulate these processes in a basal marsupial species. The gray short-tailed opossum Monodelphis domestica resembles the presumed mammalian morphotype. It provides an alternative model to understand the process of lung development in mammals from an evolutionary point of view. The broncho-alveolar lungs in mammals have evolved to fulfill multiple functions related to terrestrial living and breathing air, however the most important function is to facilitate gas exchange. To achieve this goal, the mammalian lung consists of two branched, tree-like systems—the airways and the vasculature—that develop in a coordinated way from the primary bud stage to the generation of millions of alveolar gas exchange units. The process of lung maturation and the molecular mechanisms involved in lung development were investigated primary in traditional eutherian model organisms. However, to identify the developmental mode in the morphotype of the mammalian lung, the investigation of basal mammalian groups, such as marsupials, is essential. Since the process of lung development takes place largely intrauterine in the eutherian fetus, the structural prerequisites of a functioning lung are difficult to assess. In this regard, marsupials offer a model for studying lung development because the lung maturation is shifted to the postnatal period. An established breeding colony of Monodelphis domestica provides the basis for the ontogenetic stages required for the planned research project. The combination of histological, ultrastructural (TEM, SEM), Micro-CT (3-D reconstruction) techniques allows for a comprehensive morphological and morphometric description of the lung development. The timely and local expression of 11 candidate genes, known to be relevant for lung development, will be analyzed by In situ hybridization (ISH) on histological serial sections. The proposed project will draw a comparison to established eutherian models and questions if the same gene regulatory processes apply to the basal mammalian species or if there are spatial and temporal alterations of gene expression correlated with early lung functionalization. The aim of the project is to identify, locate and confirm factors involved in the maturation of the Monodelphis lung and draw conclusions to basic evolutionary patterns of mammalian lung development.