Developmental Mechanisms for the Evolution of Bone Loss

项目概要/摘要 骨质流失疾病，包括骨质疏松症，是美国老龄化的一个重大且日益严重的威胁 人口。退行性骨质减少是一种具有环境和遗传因素的复杂特征，可能 是由于自然选择的强度降低而导致的，以维持后骨骼生成的稳健性 生殖个体。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。我们应用进化突变的创新策略 骨质疏松的南极鱼类骨骼建立了人类疾病模型，这些鱼类的祖先拥有强大的 骷髅。由于南极鱼类某些谱系对致密骨骼的自然选择减少，骨骼 骨质减少，使动物能够栖息在水体中并利用其丰富的资源。相关 保留着致密骨骼的谱系继续在海底觅食。拟议工作的目标是 描述具有骨质减少和正常骨骼的物种之间的遗传和表型差异， 从而确定人类骨退行性疾病的新候选基因和机制。我们的 假设是突变要么下调基因的活性，要么正向调节 成骨或上调对成骨产生负面影响的基因活性，从而解释了进化 骨骼减少与骨骼坚固的相关物种之间的差异。目标 1 将确定以下阶段： 骨质减少物种 Chaenocephalus aceratus（黑鳍冰鱼）的骨骼发育存在差异 以及相关的强骨化物种 Notothenia coriiceps（黄腹石鳕），使用软骨染色剂， 骨和细胞外基质分子，以及骨骼标记基因的表达。目标2将使用高 高通量 cDNA 测序，比较致密和成骨组织的基因表达谱 僵化不良的物种作为识别两个物种之间的监管差异的手段。目标3将 使用损失定义骨骼调节基因在骨化骨骼发育中的功能作用 三刺刺鱼的功能和功能获得实验。刺鱼，一种与 我们的南极鱼拥有完整测序的基因组，并且易于基因敲除和 在实验室进行转基因。意义。这些实验将揭示 在自然选择的力量下，其活性发生变化的基因可以减少骨骼骨化 南极鱼。因为随着进化时间的推移，骨矿化的减少模拟了人类骨质流失 随着发育时间的推移疾病的发生，这些研究有可能识别新基因，并提供新的 对骨质减少、骨质疏松症和其他可利用的骨消耗疾病的机制的见解 开发治疗人类疾病的新疗法。项目叙述 拟议的实验将揭示活动发生变化的基因的身份和功能， 在自然选择的力量下，导致某些南极鱼类谱系的骨矿物质密度丧失。 因为南极鱼类在进化过程中骨矿化的减少类似于 人类随着年龄的增长而骨密度随着发育时间的推移而变化，拟议的研究有可能 识别新基因，并为低骨矿物质密度、骨质疏松症和骨质疏松症的机制提供新的见解 其他可用于开发人类疾病新疗法的骨消耗疾病。

Project Summary/Abstract 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 icefish) and the related robustly ossified species Notothenia coriiceps (yellowbelly rockcod) 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.