Mutagenesis of Tbx3: a model of ulnar-mammary syndrome

描述（由申请人提供）：T盒基因编码一个转录因子家族，该家族在多种组织中表达，并在发育过程中的不同遗传途径中发挥作用。人类TBX 3和TBX 5的突变分别导致常染色体显性遗传、尺乳综合征（UMS）和Holt-Oram综合征，而TBX 1缺乏导致人类22 q11缺失综合征。UMS患者有先天性肢体、顶浆腺、牙齿和生殖器畸形。破坏DNA结合的TBX 3功能丧失突变可能导致某些UMS病例。其他突变发生在蛋白质-蛋白质相互作用所需的区域或破坏调节（激活剂或阻遏物）功能。在受影响的人中未检测到基因型-表型相关性。小鼠Tbx 3无效杂合子不表现UMS表型，大多数纯合无效突变体在妊娠中期死亡。因此，确定Tbx 3缺陷在发育肢体的不同区域或其他器官中的特定影响，需要小鼠Tbx 3的条件突变。该项目的目标是产生Tbx 3破坏和功能障碍的条件小鼠模型，并研究Tbx 3突变导致出生缺陷的分子和细胞机制，重点是肢体。我们将有条件地破坏Tbx 3功能，并使用重组酶介导的盒交换来突变不同的Tbx 3蛋白功能结构域。将检查基因表达、细胞分化、迁移、增殖和存活的改变。我们已经发现了一种新的表型，由于显性负效应的外显子7突变，并建议分析其转录功能。基因型-表型相关性也可以被定义为指导人类UMS的新研究。我们提出的灵活的模型系统将是一个有价值的工具，许多器官的发育研究，并导致更深入地了解人类先天性异常的遗传和分子基础。

DESCRIPTION (provided by applicant): T-box genes encode a family of transcription factors that are expressed in multiple tissues and function in diverse genetic pathways during development. Mutations in humanTBX3 and TBX5 result in autosomal dominant, ulnar-mammary (UMS) and Holt-Oram syndromes, respectively, and TBX1 deficiency contributes to human deletion 22q11 syndromes. Patients with UMS have congenital limb, apocrine gland, tooth, and genital abnormalities. TBX3 loss-of-function mutations that disrupt DNA binding may cause some cases of UMS. Other mutations occur in regions required for protein-protein interactions or disrupt regulatory (activator or repressor) function. No genotype-phenotype correlations have been detected in affected humans. Murine Tbx3 null heterozygotes do not manifest the UMS phenotype and most homozygous null mutants die in midgestation. Thus, determining the specific effects of Tbx3 deficiency in different regions of the developing limb, or in other organs, requires conditional mutation of murine Tbx3. The goal of this project is to generate conditional mouse models of Tbx3 disruption and dysfunction and examine the molecular and cellular mechanisms by which mutations of Tbx3 cause birth defects, with an emphasis on the limb. We will disrupt Tbx3 function conditionally and use recombinase -mediated cassette exchange to mutate distinct Tbx3 protein functional domains. Alterations in gene expression, cellular differentiation, migration, proliferation and survival will be examined. We have already discovered a novel phenotype due to dominant negative effects of an Exon 7 mutation and propose to analyze its transcriptional function. Genotype -phenotype correlations may also be defined to direct new investigations in humans with UMS. The flexible model system we propose will be a valuable tool for developmental studies of many organs and lead to a deeper understanding of the genetic and molecular bases of congenital anomalies in humans.