Molecular and Genetic Regulation of Craniofacial Development

项目摘要 颅面畸形占所有出生缺陷的近三分之一，是发病的严重原因， 婴儿死亡率。尽管它们普遍存在，但引起这些疾病的潜在遗传和分子机制， 大多数颅面缺损仍不为人所知。拟议研究的长期目标是确定 控制颅面发育以再生为目的的分子和遗传途径， 修复，组织工程，以及先天性颅面出生缺陷的诊断和干预。 具体地说，本申请集中于识别转录途径和机制 与颅面发育有关最近的工作为皮埃尔·罗宾确定了一种新的遗传模型 序列（PRS）。每800例活产婴儿中约有1例发生PRS，其特点是低血糖和高血糖。 下颌、舌位置不当和腭后裂，可导致上呼吸道阻塞 进食困难。以前，人们认为PRS是由环境因素引起的， 限制下颌骨的生长，但现在很清楚，这个序列也有一个不确定的遗传 组件。携带Dlx 5/6基因座的一个突变等位基因和Mef2c等位基因的一个突变拷贝的小鼠在24小时死亡。 出生时有类似PRS的颅面缺陷。Dlx5/6基因座编码两个与Distal无关的同源框 Mef2c基因座编码MADS盒转录因子，而Mef2c基因座编码MADS盒转录因子。除了它们 在遗传相互作用中，MEF2C和Dlx5合作以诱导稳健的协同转录应答。的 该提议的基础假设是Dlx 5/6和MEF 2C在下游形成转录复合物 内皮素受体信号传导，这种复合物是必不可少的激活一个子集的基因， Dlx5/6-MEF2C基因的突变或异常表达是颅面发育所必需的， 基因导致颅面畸形比如PRS为了解决这些假设，三个具体目标 被提议。目的1将定义Dlx5和MEF2C之间的物理和功能相互作用，以及这种相互作用是如何发生的。 导致转录激活。目的是确定控制基因的转录机制， 在颅面发育过程中的表达。目的2：分析Mef2c-Dlx 5/6双颌畸形的颅面缺损 杂合子的详细信息。目的是确定下颌骨潜在的可能细胞机制， 双杂合子的腭表型，以了解这些过程如何控制腭闭合和颌骨 增长目的3将鉴定颅面间充质中Mef2c转录的上游调控因子， 使用转基因小鼠确定Mef2c是否是内皮素信号通路的直接靶点 approach.目标是将Mef2c置于转录途径中，并确定Mef2c的直接表达。 颅面发育中内皮素信号的转录效应子。

PROJECT SUMMARY Craniofacial anomalies account for nearly one-third of all birth defects and are a severe cause of morbidity and mortality in infants. In spite of their prevalence, the underlying genetic and molecular mechanisms causing most craniofacial defects remain largely unknown. The long-term goal of the proposed studies is to define the molecular and genetic pathways that control craniofacial development for the purpose of regeneration and repair, tissue engineering, and the diagnosis of and intervention into congenital craniofacial birth defects. Specifically, this application is focused on the identification of the transcriptional pathways and mechanisms involved in craniofacial development. Recent work has identified a novel genetic model for Pierre Robin Sequence (PRS) in mice. PRS occurs in about 1 in every 800 live births and is characterized by small lower jaw, improperly positioned tongue and posterior cleft of the palate, which can result in upper airway obstruction and feeding difficulties. Previously, it was thought that PRS occurred as a result of environmental factors that restrict outgrowth of the mandible, but it is now quite clear that this sequence also has an undefined genetic component(s). Mice that carry one mutant allele of Dlx5/6 locus and one mutant copy of the Mef2c allele die at birth from craniofacial defects resembling PRS. The Dlx5/6 locus encodes two Distal-less related homeobox transcription factors, while the Mef2c locus encodes a MADS box transcription factor. In addition to their genetic interaction, MEF2C and Dlx5 cooperate to induce a robust synergistic transcriptional response. The hypotheses underlying this proposal are that Dlx5/6 and MEF2C form a transcriptional complex downstream of endothelin receptor signaling, that this complex is essential for the activation of a subset of genes that are required for craniofacial development, and that mutations or aberrant expression of Dlx5/6-MEF2C target genes contributes to craniofacial anomalies such as PRS. To address these hypotheses, three specific aims are proposed. Aim 1 will define the physical and functional interaction between Dlx5 and MEF2C and how this results in transcriptional activation. The goal is to define the transcriptional mechanisms that control gene expression during craniofacial development. Aim 2 will analyze the craniofacial defects in Mef2c-Dlx5/6 double heterozygotes in detail. The goal is to identify possible cellular mechanisms underlying the mandible and palate phenotypes in double heterozygotes to understand how these processes control palate closure and jaw growth. Aim 3 will identify upstream regulators of Mef2c transcription in craniofacial mesenchyme and will determine whether Mef2c is a direct target of the endothelin signaling pathway, using a transgenic mouse approach. The goals are to place Mef2c into a transcriptional pathway and to identify the immediate transcriptional effectors of endothelin signaling in craniofacial development.