Six1 Co-factors in Craniofacial Development

BOS以包括畸形在内的颅面缺陷为特征。 腮弓(BAS)、外耳、中耳和内耳；一部分患者也有肾脏缺陷。 有两个致病基因与BOS诊断有关，但这两个基因占不到一半 患者：SIX1转录因子和辅助因子蛋白EYA1，它与SIX1结合并修改其 转录活性。因此，超过一半的BOS患者的致病基因尚未确定。我们 假设还有其他关键的辅因子蛋白与SIX1结合来调节其活性，并且 这些辅助因子的突变导致了BOS的未知原因。这项研究的目的是 程序的目的是在易处理的模型系统中识别其功能改变对 BOS的头面部畸形，使这些基因最终可以纳入人类基因筛查。 利用果蝇的SIX1同源基因的互作组数据，我们鉴定了11个新的可能的辅助因子 在非洲爪哇，并表明，大多数表达在发育中的底部，耳朵和肾脏，因此 可能与BOS相关。这些蛋白质在人类中高度保守，我们的初步数据显示 其中5个基因(Sobp、Zmym2、Zmym4、2G4、MCRS1)是胚胎发育所必需的 鳃弓(神经脊[NC])、中耳(NC)和内耳(外耳胎盘)的前体。在目标1中， 我们将使用增益法和损失法来确定这些候选辅助因子是否起作用 NC的形成或迁移、颧弓软骨或内耳基因的表达和形成。在目标2中，我们 将评估这些基因产物与SIX1的生化相互作用以及它们是否影响SIX1 转录功能。在目标3中，我们将确定SIX1中已知的BOS突变是否会影响候选 辅因子结合或功能，并绘制SIX1和OF的蛋白质-蛋白质相互作用域的哪些区域 每个辅因子调节结合和转录活性。我们以前的工作和建立的模型系统 独特的地位，我们来验证这些候选是否是骨性的SIX1辅助因子，并阐明它们是如何 有助于正常和畸形的头面部发育。这些分析将提供重要的 从有限的患者资料中无法获得的信息。他们也有未来 有可能解释BOS患者的表型变异，并为纳入新的 BOS基因面板中的致病基因。

Branchiootorenal spectrum disorders (BOS) are characterized by craniofacial defects that include malformation of branchial arches (BAs), external ear, middle ear, and inner ear; a subset of patients also has kidney defects. Two causative genes are associated with BOS diagnoses, but these genes account for fewer than half of patient cases: the SIX1 transcription factor and a co-factor protein, EYA1, which binds to SIX1 and modifies its transcriptional activity. Thus, the causative genes for over half of BOS patients are yet to be identified. We hypothesize that there are other key co-factor proteins that bind to SIX1 to regulate its activity, and that mutations in these co-factors contribute to the unknown causes of BOS. The goal of this research program is to identify, in tractable model systems, additional genes whose altered functions contribute to the craniofacial malformations of BOS so that these genes can ultimately be included in human genetic screening. Using the Drosophila interactome data for the fly homologue of Six1, we identified 11 novel putative co-factors in Xenopus and showed that most of these are expressed in the developing BAs, ear and kidney, and therefore are potentially relevant to BOS. These proteins are highly conserved in humans, and our preliminary data show that five of them (Sobp, Zmym2, Zmym4, 2G4, Mcrs1) are required for development of the embryonic precursors of the branchial arches (neural crest [NC]), middle ear (NC) and inner ear (otic placode). In Aim 1, we will use gain- and loss-of-function approaches to determine whether these candidate cofactors play a role NC formation or migration, branchial arch cartilages or inner ear gene expression and formation. In Aim 2, we will evaluate the biochemical interactions of these gene products with Six1 and whether they affect Six1 transcriptional function. In Aim 3, we will determine whether the known BOS mutations in SIX1 affect candidate co-factor binding or function, and map what regions of the protein-protein interaction domains of Six1 and of each co-factor mediate binding and transcriptional activity. Our previous work and established model systems uniquely position us to validate whether these candidates are bone fide Six1 co-factors, and elucidate how they contribute to normal and dysmorphic craniofacial development. These analyses will provide important information that cannot be obtained from the limited patient material available. They also have the future potential to explain the phenotypic variability in BOS patients and provide a rationale for including new causative genes in BOS gene panels.