Developmental Mechanisms for the Evolution of Bone Loss

项目摘要/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。退行性骨质疏松症是一种与环境和遗传因素有关的复杂特征，可能 都是由于自然选择的强度降低，以保持强劲的骨生产后 生殖个体。这种复杂特征的自然变异存在于某些脊椎动物谱系中，导致 继发性骨质疏松症的适应性进化。我们采用了进化变异的创新策略 人类疾病模型到南极鱼类的骨骼，它们的祖先拥有健壮的 骷髅。随着对密集骨骼的自然选择在某些南极鱼类谱系中减弱，骨骼 变得嗜骨性，使动物能够栖息在水柱中并利用其丰富的资源。相关 保留密集骨骼的血统继续在海底觅食。拟议工作的目标是 描述骨质疏松症和正常骨骼物种之间的遗传和表型差异， 从而确定人类骨骼退行性疾病的新的候选基因和机制。我们的 假说是，要么下调正向调控基因活性的突变 成骨或上调负面影响成骨的基因的活性是进化的原因 骨质疏松性骨骼与健壮骨骼相关物种的差异。目标1将确定在哪些阶段 在骨量稀少的物种中，刺头鱼(黑鳍银鱼)的骨骼发育存在差异 以及与之相关的强壮的硬骨化物种尖吻鳕鱼(黄腹石鳕鱼)，用软骨染色， 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HIGH- 比较密闭性和非致密性骨骼发育组织的基因表达谱 僵化程度较低的物种作为识别两个物种之间调控差异的一种手段。目标3将 利用Lost-1确定骨骼调节基因在骨化骨骼发育中的功能作用 三刺鱼的功能和功能增益实验。刺鱼，一种与 我们的南极鱼，有一个完全测序的基因组，并服从于基因敲除和 实验室中的转基因。意义重大。这些实验将揭示细胞的身份和功能 在自然选择的力量下，活性发生变化的基因，以减少骨骼的骨化 南极鱼。因为随着进化时间的推移，骨骼矿化的减少模拟了人类的骨丢失 随着疾病的发展，这些研究有可能识别新的基因，并提供新的 对骨量减少、骨质疏松症和其他可利用的骨消耗性疾病的机制的见解 开发治疗人类疾病的新疗法。项目叙事 拟议中的实验将揭示其活性发生变化的基因的身份和功能， 在自然选择的力量下，导致某些南极鱼类的骨密度丧失。 因为随着进化时间的推移，南极鱼类骨骼矿化的减少与 随着年龄的增长，人类的骨密度随着发育时间的推移，拟议的研究有可能 确定新的基因，并为低骨密度、骨质疏松症和骨质疏松症的机制提供新的见解 其他可被利用来开发治疗人类疾病的新疗法的骨损耗障碍。

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.