Mexican tetra (Astyanax mexicanus) as a model to understand the development and regeneration of the epithelial appendages

穴居动物是退化进化的经典例子；然而，它们也进化出了建设性的特征，以弥补永久黑暗中的生活。墨西哥小淡水鱼（Astyanax mexicanus）是一种新颖的动物模型，存在两种形态类型：有眼、有色素的表层鱼（surface fish /SF）和无眼、无色素的穴居鱼（cavefish /CF）。为了更好地适应地下环境，CF进化出了形态、感觉和行为特征。CF有增强的上皮结构，包括牙齿、味蕾（TBs）和神经肥大细胞（NMC）。NSERC DG项目的长期目标是利用墨西哥四环蛇作为动物模型，确定脊椎动物上皮附属物发育和再生的机制。在墨西哥tetra中，我们发现不同的眼睛表型在牙齿数量、形态、图案和SF头部一侧晶状体的去除上都有变化，改变了颅面区域的基因表达。基于这些发现，我假设CF在上皮附属物的发育和再生中具有先进的细胞和分子机制。我解决这一假设的短期目标是：***1)了解眼睛变性对颅面区域上皮附属物发育和再生的影响。我们将使用组织学和胚胎操作技术来确定与上皮附属物发育和再生相关的变化的遗传基础。此外，该数据将强调Shh （Sonic Hedgehog）过表达对该物种上皮附属物发育的任何可能的梯度效应。***2)研究神经嵴细胞（NCC）迁移对CF上皮附属物发育的影响。细胞标记和NCC移植技术将用于比较SF和CF在不同发育阶段的NCC的迁移模式。这些数据将证明NCC的迁移行为的改变及其对颅面发育的影响。***3)探讨胚层起源在上皮附属物图案化中的适应性意义。利用细胞标记技术和基因表达分析，我们将比较外胚层来源的上皮附属物和内胚层来源的附属物。这些数据将为该物种上皮附属物发育的微观进化机制提供见解。***意义：通过我的HQP，我们将推进对上皮附属物发育和再生机制的理解，同时赋予HQP在发育和分子细胞生物学技术方面的宝贵技能。这些是组织工程、兽医和水产养殖应用中的生物研究所需要的。总之，该计划将增加我们对脊椎动物上皮附属物基本发育机制的理解。*****

Cave dwelling animals are classic examples of regressive evolution; however, they also have evolved constructive features to compensate for life in perpetual darkness. The small fresh water fish, Mexican tetra (Astyanax mexicanus), is a novel animal model and exists as two morphological types: an eyed, pigmented surface-dwelling form (surface fish /SF) and an eyeless, unpigmented cave-dwelling form (cavefish /CF). The CF have evolved with morphological, sensory and behavioural traits for better adaptation to a subterranean environment. CF have enhanced epithelial structures, including teeth, taste buds (TBs) and neuromast cells (NMC). The long-term goal of this NSERC DG program is to identify the mechanisms underlying the development and regeneration of the epithelial appendages of vertebrates using Mexican tetra as an animal model. In Mexican tetra, we found different eye phenotypes have variation in tooth number, morphology, patterning and removal of the lens on one side of the head of SF altered the gene expression in the craniofacial region. Based on these findings, I hypothesize CF has advanced cellular and molecular mechanisms for the development and regeneration of epithelial appendages. My short-term objectives to address this hypothesis are: ***1) To understand the effect of eye degeneration on the development and regeneration of epithelial appendages in the craniofacial region. We will use histological and embryo manipulation techniques to identify the genetic basis for changes associated with epithelial appendage development and regeneration. Further, this data will highlight any possible gradient effect of Shh (Sonic Hedgehog) overexpression on epithelial appendage development in this species. ***2) To characterise the influence of neural crest cell (NCC) migration on CF epithelial appendage development. Cell labeling and NCC transplantation techniques will be used to compare the migratory pattern of the NCC of SF and CF at different developmental stages. This data will demonstrate the altered migratory behaviour of the NCC and its effect on craniofacial development. ***3) To investigate the adaptive significance of germ layer origin in patterning the epithelial appendages. Using cell labeling techniques and gene expression analysis we will compare the ectodermal derived epithelial appendages with endodermal derived appendages. This data will provide insight to the microevolutionary mechanisms of epithelial appendage development of this species. ***Significance: With my HQP we will advance the understanding of the development and regenerative mechanisms of the epithelial appendages while giving HQP valuable skill set in developmental and molecular cell biology techniques. These are needed for the biological research in tissue engineering, veterinary and aquaculture applications. In summary, the proposed program will increase our understanding of the fundamental developmental mechanisms of epithelial appendages in vertebrates.*****