SoxE gene regulation of Type II collagen in the sea lamprey Petromyzon marinus

描述（由申请人提供）：所有脊椎动物，包括人类，都含有分泌软骨基质的软骨细胞，但脊椎动物软骨形成机制的起源尚不清楚。Sox9是一种表达于神经嵴的HMG-box转录因子，调节II型胶原（Col2a1）的表达，Col2a1是脊椎动物软骨的主要基质蛋白。Sox9是Sox基因SoxE亚家族的成员。最近的研究表明，SoxE基因在低等脊椎动物鳃弓软骨的正常发育和咽囊的形成中起着至关重要的作用。本研究旨在阐明SoxE基因SoxE1、SoxE2和SoxE3在海七鳃鳗鳃弓软骨形成过程中的作用。目前的项目有两个具体目的：(1)确定SoxE基因是否在发育中的咽部交叉调控自身表达；(2)确定SoxE基因是否调控Col2a1在七鳃鳗体内的表达。结合分子技术，包括过表达，morpholino敲除，和原位杂交将被使用。这项研究将有助于实现两个目标。主要目的是确定Col2a1是否受多个SoxE基因的调控。患有Sox9单倍体缺陷的人的特征是先天性发育不良，这是一种以骨骼异常为特征的半致死性骨软骨发育不良，而Sox9单倍体缺陷的小鼠在围产期死亡之前会出现腭裂，这表明在哺乳动物（包括人类）中，正常的颅面和骨骼发育需要两个功能正常的Sox9拷贝。这项研究将为了解早期脊椎动物软骨形成过程中单个Sox9基因的多个拷贝表达是否可能源于早期脊椎动物软骨形成神经嵴中多个Sox9因子的表达提供背景。第二个目标是确定SoxE基因是否调节其他SoxE转录因子在七鳃鳗中的表达。在迄今为止研究的脊椎动物模型中，Sox9和Sox10具有部分重叠的表达域，Sox10的过表达或功能缺失可影响Sox9的表达，提示这些相关基因之间存在调控相互作用。本研究将确定在脊椎动物历史的早期，在单个祖先SoxE基因重复之后，是否需要多个SoxE基因拷贝来形成适当的软骨形成，并将为进一步研究揭示SoxE转录因子控制软骨形成和咽部模式机制的起源奠定基础。该项目旨在确定在原始脊椎动物中，SoxE转录因子的复制对所有脊椎动物软骨发育的适当控制是如何重要的。由于Sox9的其他作用并不依赖于多拷贝，因此了解Sox9基因（Sox9）的专一性多功能拷贝对胶原表达的调节是如何产生的将是有价值的。由于更深入地了解Sox9对软骨形成的控制取决于对其在早期脊椎动物中可能出现的作用的理解，因此这项研究服务于更大的公共利益，因为它将阐明人类软骨形成病理的起源，例如镰状细胞发育不良，依赖于多种功能Sox9等位基因来正确表达II型胶原和软骨形成。

DESCRIPTION (provided by applicant): All vertebrates, including humans, contain chondrocytes that secrete a cartilaginous matrix, but the origin of chondrogenic mechanisms within the vertebrates is not well understood. Sox9 is an HMG-box transcription factor expressed in the neural crest that regulates expression of Type II collagen (Col2a1), the major matrix protein in vertebrate cartilage. Sox9 is a member of the SoxE subfamily of Sox genes. Recent research indicates SoxE genes play an essential role in proper development of branchial arch cartilage and formation of pharyngeal pouches in lower vertebrates. The research described in this proposal will elucidate the function of SoxE genes, SoxE1, SoxE2 and SoxE3, during chondrogenesis of the branchial arches in the sea lamprey Petromyzon marinus. The current project has two Specific Aims: (1) to determine if SoxE genes cross-regulate their own expression in the developing pharynx; (2) to determine if SoxE genes regulate expression of Col2a1 in the sea lamprey. A combination of molecular techniques, including overexpression, morpholino knock-down, and in situ hybridization will be used. This research will contribute to two goals. The primary goal is to determine if Col2a1 is regulated by multiple SoxE genes. People who suffer from haploinsufficiency of Sox9 are characterized by campomelic dysplasia, a semilethal osteochondrodysplasia characterized by skeletal abnormalities, and mice haploinsufficient for Sox9 develop cleft palate prior to perinatal death, suggesting two functioning copies of Sox9 are required for normal craniofacial and skeletal development in mammals, including humans. This research will form the background for understanding if the need for expression of multiple copies of the single Sox9 gene during chondrogenesis may have arisen from multiple SoxE factors expressed in the chondrogenic neural crest in early vertebrates. The secondary goal is to determine if SoxE genes regulate the expression of other SoxE transcription factors in the lamprey. In vertebrate models studied to date, Sox9 and Sox10 have partially overlapping expression domains and overexpression or loss of function of Sox10 can affect the expression of Sox9, suggesting regulatory interaction between these related genes. This research will determine if the requirement of multiple copies of SoxE genes for proper chondrogenes may have arisen early in vertebrate history following duplication of a single ancestral SoxE gene, and will form the basis for further investigation to uncover the origin of the control of chondrogenesis and pharyngeal patterning mechanisms by SoxE transcription factors. This project seeks to determine in a primitive vertebrate, how duplication of SoxE transcription factors may be important for proper control of cartilage development in all vertebrates. It will be valuable to understand how the regulation of collagen expression by obligate multiple functioning copies of a SoxE gene (Sox9) arose since other roles of Sox9 do not depend on multiple copies. Since a greater understanding of the control of chondrogenesis by Sox9 depends on understanding this role where it may have arisen in early vertebrates, this study serves the greater public good because it will shed light on the origin of chondrogenic pathologies in humans, such as campomelic dysplasia, that depend on multiple functioning Sox9 alleles for proper expression of type II collagen, and chondrogenesis.