Developmental Mechanisms for the Evolution of Bone Loss

描述（由申请人提供）：骨丢失疾病，包括骨质疏松症，是美国老龄人口的一个重大和日益增长的威胁。退行性骨质减少是一种具有环境和遗传成分的复杂性状，并且可能是由于自然选择的强度降低而引起的，以维持生殖后个体的稳健骨生成。这种复杂性状的自然变异存在于某些脊椎动物谱系中，导致继发性骨质减少的适应性进化。我们将人类疾病的进化突变模型的创新策略应用于骨质疏松南极鱼的骨骼，其祖先拥有强大的骨骼。随着对南极鱼类某些谱系中致密骨骼的自然选择减少，骨骼变得骨质减少，使动物能够栖息在水柱中并利用其丰富的资源。保持密集骨架的相关谱系继续在海底觅食。这项工作的目标是描述骨质疏松和正常骨骼物种之间的遗传和表型差异，从而确定人类骨退化疾病的新候选基因和机制。我们的假设是，无论是下调基因的活性，积极调节成骨或上调基因的活性，对成骨的负面影响占骨质疏松与健全的骨骼相关物种的进化差异。目的1将确定骨骼发育分化的阶段之间的骨质减少物种Chaenocephalus aceratus（黑鳍冰鱼）和相关的健壮骨化物种Notothenia coriiceps（黄腹岩鳕鱼）使用染色软骨，骨，细胞外基质分子，和骨骼标记基因的表达。目的2将使用高通量cDNA测序来比较来自致密和低骨化物种的成骨组织的基因表达谱，作为鉴定两个物种之间调控差异的手段。目的3将使用三棘刺鱼的功能丧失和功能获得实验来定义骨骼调节基因在僵化骨骼发育中的功能作用。棘背鱼是与我国南极鱼类有亲缘关系的模式物种，其基因组序列已完全测序，可在实验室进行基因敲除和转基因。 重要性：这些实验将揭示基因的特性和功能，在自然选择的力量下，这些基因的活性发生了变化，以减少南极鱼骨骼的骨化。由于随着进化时间的推移，骨矿化的减少模拟了随着发育时间的推移人类骨丢失疾病，因此这些研究有可能识别新的基因，并为骨质减少、骨质疏松症和其他骨消耗疾病的机制提供新的见解，这些机制可用于开发人类疾病的新疗法。 项目叙述：拟议的实验将揭示在自然选择的力量下，导致南极鱼类某些谱系骨矿物质密度损失的基因的活动发生变化的特性和功能。由于南极鱼在进化过程中骨矿化的减少与人类在发育过程中骨密度的减少相似，因此拟议的研究有可能发现新的基因，并为低骨密度、骨质疏松症和其他骨消耗疾病的机制提供新的见解，这些机制可用于开发人类疾病的新疗法。

DESCRIPTION (provided by applicant): Bone loss diseases, including osteoporosis, are a significant and increasing threat for America's aging population. Degenerative osteopenia is a complex trait with environmental and genetic components, and may have arisen from a reduction in the strength of natural selection to maintain robust bone production in post- reproductive individuals. Natural variation for this complex trait exists in certain vertebrate lineages leading to the adaptive evolution of secondary osteopenia. We apply the innovative strategy of evolutionary mutant models for human disease to the skeletons of osteopenic Antarctic fish, whose ancestors possessed robust skeletons. As natural selection for dense bones diminished in certain lineages of Antarctic fish, the skeleton became osteopenic, allowing animals to inhabit the water column and exploit its abundant resources. Related lineages that retain dense skeletons continue to forage on the ocean floor. The goal of the proposed work is to characterize the genetic and phenotypic differences between species with osteopenic and normal skeletons, and thereby identify new candidate genes and mechanisms for human bone degeneration diseases. Our hypothesis is that mutations that either down-regulate the activity of genes that positively regulate osteogenesis or up-regulate the activity of genes that negatively affect osteogenesis account for evolved differences in related species with osteopenic versus robust skeletons. Aim 1 will identify the stages at which skeletal development diverges between the osteopenic species Chaenocephalus aceratus (blackfin ice fish) and the related robustly ossified species Notothenia coriiceps (yellowbelly rock cod) using stains for cartilage, bone, and extracellular matrix molecules, and the expression of skeletal marker genes. Aim 2 will use high- throughput cDNA sequencing to compare gene expression profiles of skeletogenic tissues from densely and poorly ossified species as a means to identify regulatory differences between the two species. Aim 3 will define the functional roles of skeletal regulatory genes in the development of the ossified skeleton using loss- of-function and gain-of-function experiments in three-spine stickleback. Stickleback, a model species related to our Antarctic fish, has a completely sequenced genome, and is amenable to gene knockdown and transgenesis in the laboratory. Significance: These experiments will reveal the identities and functions of genes whose activities have changed, under the force of natural selection, to reduce skeletal ossification in Antarctic fish. Because the reduction of bone mineralization over evolutionary time mimics human bone loss diseases over developmental time, these studies have the potential to identify new genes, and provide new insights into mechanisms for osteopenia, osteoporosis, and other bone wasting disorders that can be exploited to develop novel therapies for human disease. Project Narrative: The proposed experiments will reveal the identities and functions of genes whose activities have changed, under the force of natural selection, leading to loss of bone mineral density in certain lineages of Antarctic fish. Because the reduction of bone mineralization over evolutionary time in Antarctic fish mimics the reduction of bone density in humans as they age over developmental time, the proposed studies have the potential to identify new genes, and provide new insights into mechanisms for low bone mineral density, osteoporosis, and other bone wasting disorders that can be exploited to develop novel therapies for human disease.