Msx2 function in tooth crown morphogenesis

Msx2在牙冠形态发生中的功能

• 批准号: 7295561
• 负责人: MARIANNA BEI
• 金额: $ 8.75万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7295561
• 关键词: Affect; BMP4; CDKN1A gene; Cell Proliferation; Complex; Defect; Dental; Dental Enamel; Dental Enamel Hypoplasia; Dental crowns; Development; Disease; Ectodermal Dysplasia; Epithelial; Epithelium; Erinaceidae; Exhibits; Fibroblast Growth Factor; Genes; Genetic; Height; Homeobox Genes; In Vitro; Knockout Mice; Localized; Location; Mediator of activation protein; Molecular; Molecular Biology; Molecular Genetics; Morphogenesis; Mus; Mutate; Organ Culture Techniques; Pathogenesis; Pathway interactions; Pattern; Process; Research; Role; Shapes; Signal Transduction; Signaling Protein; Structure; Testing; Tooth Crowns; Tooth structure; Transforming Growth Factors; Transgenic Organisms; appendage; base; craniofacial; gene function; in vivo; insight; mutant; oncoprotein p21; research study; tooth cusp

DESCRIPTION (provided by applicant): Teeth are epithelial appendages whose morphogenesis is regulated by conserved signaling cascades. The patterning and shape of tooth crowns is determined by the location, orientation, shape and height of tooth cusps, and by the proliferation and folding of the adjacent epithelium. At the molecular level, the patterning and shape of tooth crowns is controlled by signals and their transcriptional mediators derived from the enamel knot, an epithelial structure considered the organizing center for tooth morphogenesis. More than 10 signaling proteins have restricted expression in the enamel knots, including fibroblast growth factors (FGFs), hedgehog (HH), WNTs and transforming growth factor b (TGFb) superfamilies as well as mediators of signaling such as p21, Edar, Lef1 and Msx2. Mice lacking the homeobox gene Msx2 exhibit defects in crown morphogenesis. Our studies show that in the Msx2 knock out mice (i) the cusps are formed but they are misshapen, (ii) the folding of the dental epithelium is aberrant in the molars exhibiting localized, increased cell proliferation and that (iii) Bmp4 signaling in the enamel knot is Msx2-dependent suggesting that Bmp4 and Msx2 genes function within the same genetic pathway. These observations serve as the basis for our proposed hypothesis that an Msx2-dependent signal BMP4 is a potential major effector of the Msx2 function in the enamel knot by controlling the shape of cusps and crown normal morphogenesis. In this context and to further investigate the role of Msx2 during tooth development, we will (i) identify genes regulated by Msx2 in the enamel knot, by investigating the expression patterns of genes that, like Bmp4, are co-expressed with Msx2 in the enamel knot and (ii) determine whether the Msx2 downstream gene, BMP4, is a major effector of the Msx2 function in the enamel knot, by testing the sufficiency of BMP4 to rescue the cusp shape and crown morphogenesis defect in vitro and in vivo. Collectively these experiments should define a regulatory hierarchy between Msx2 and its downstream gene Bmp4 in both genetic and molecular terms during late tooth development and provide a molecular framework for understanding cusp shape and crown morphogenesis. Narrative: Teeth are epithelial appendages whose morphogenesis is regulated by complex genetic pathways. Several craniofacial and ectodermal dysplasia disorders affect tooth development by affecting their early development (tooth agenesis) or late development (dysplastic crown, enamel hypoplasia). Msx2 mutant teeth are dysplastic, exhibiting crown shape abnormalities. Although, Msx2 is critical for tooth crown morphogenesis when mutated, its function remains unknown. This project aims at understanding the role of Msx2 in the pathogenesis of tooth dysmorphias. To accomplish this aim, a search for genes regulated by Msx2 will be conducted, using powerful molecular biology, transgenic and organ culture approaches. It is anticipated that these results will provide valuable insight on the function of Msx2 gene, on the pathogenetic mechanism of tooth development and may also provide valuable information towards treatment of tooth dysmorphias. 4

描述（由申请人提供）：牙齿是上皮附属物，其形态发生受保守的信号级联调节。牙冠的图案和形状由牙尖的位置、方向、形状和高度以及邻近上皮的增殖和折叠决定。在分子水平上，牙冠的图案和形状由来自釉质结的信号及其转录介质控制，釉质结是一种上皮结构，被认为是牙齿形态发生的组织中心。超过10种信号蛋白在釉质结中有限制性表达，包括成纤维细胞生长因子（FGF）、hedgehog（HH）、WNT和转化生长因子B（TGF B）超家族以及信号介质如p21、Edar、Lef1和Msx 2。缺乏同源异型盒基因Msx2的小鼠表现出冠状形态发生的缺陷。我们的研究表明，在Msx2基因敲除小鼠中，（i）牙尖形成，但它们是畸形的，（ii）磨牙中牙上皮的折叠是异常的，表现出局部的，增加的细胞增殖，以及（iii）釉质结中的Bmp4信号是Msx2依赖性的，表明Bmp4和Msx2基因在相同的遗传途径中起作用。这些观察结果作为我们提出的假设的基础，即Msx2依赖性信号BMP 4是通过控制尖瓣和冠正常形态发生的形状在釉质结中Msx2功能的潜在主要效应子。在这种情况下，为了进一步研究Msx2在牙齿发育过程中的作用，我们将（i）通过研究在釉质结中与Msx2共表达的基因（如Bmp4）的表达模式来鉴定釉质结中受Msx2调控的基因，和（ii）确定Msx2下游基因BMP 4是否是釉质结中Msx2功能的主要效应子，通过体外和体内实验检测BMP 4对修复牙尖形态和牙冠形态缺损的作用。总的来说，这些实验应该定义Msx2和其下游基因Bmp4在遗传和分子方面在牙齿发育后期之间的监管层次，并提供一个分子框架，了解牙尖形状和冠形态发生。 叙述：牙齿是上皮附属物，其形态发生受复杂的遗传途径调节。几种颅面和外胚层发育不良疾病通过影响牙齿的早期发育（牙齿发育不全）或晚期发育（发育不良的牙冠，釉质发育不全）来影响牙齿发育。Msx2突变牙齿发育不良，表现出冠状异常。虽然Msx2在突变时对牙冠形态发生至关重要，但其功能仍然未知。本项目旨在了解Msx2在牙齿畸形发病机制中的作用。为了实现这一目标，将使用强大的分子生物学、转基因和器官培养方法来寻找Msx2调控的基因。这些结果将为阐明Msx2基因的功能、牙齿发育的发病机制以及牙齿畸形的治疗提供有价值的信息。4