DEVELOPMENTAL ROLE OF THE GENE SIX2 IN KIDNEY NEPHRON ENDOWMENT

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 与那些出生时具有典型肾单位禀赋的人相比，导致出生时肾单位数量不足的次优肾脏发育可能会产生终身后果，并与日后患心血管-肾脏疾病的显著风险相关。目前建议的长期目标是确定驱动成功的肾单位分化以实现最佳肾单位禀赋的细胞机制。具体来说，我们将探讨同源异型盒基因sine oculis 2（six 2）的作用，并确定six 2是否参与肾器官发生过程中肾单位数量的建立。使用RNAi方法，设计实验以确定在肾发生早期six 2转录的失活是否导致输尿管芽生长的显著减少，并因此导致器官型肾外植体培养物中的肾单位数的显著减少。此外，使用遗传性肾发育不全的小鼠模型，缺乏足够的表达six 2在发展过程中（Brachyrrhine（Br）突变小鼠），我们将采取系统的方法，重新引入six 2从Br小鼠制备的肾外植体，并确定是否外源six 2刺激输尿管芽的分支，导致增强的肾单位生产。此外，我们将纳入一个250 kb的Bac含有six 2基因到Br小鼠基因组中，试图增加肾单位的数量，从而挽救与six 2缺陷相关的缺陷性肾表型。在挽救之后，我们将评估成年Br小鼠中的肾生理特征是否恢复。该提议将利用显示six 2基因表达的单倍不足并且是世界上唯一工作群体的Br小鼠品系。类似地，我们已经充分表征了成年Br小鼠的生理学，其证明了高血压和慢性肾衰竭，从而促进了我们的表型拯救实验。当考虑在一起，这些实验将提供基本的见解，构成six 2在肾脏形态发生的遗传基础，并具体确定是否six 2直接决定肾单位捐赠在发展中的肾脏。这项研究的结果也将强调six 2在成人患病肾脏可能的肾单位恢复方法中的重要性。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Suboptimal kidney development resulting in an in-born deficit in nephron number can have lifelong consequences and is associated with a significant risk of cardiovascular-renal disease in later life, compared to those born with a typical nephron endowment. The long-term goal of the current proposal is to identify cellular mechanisms that drive successful nephron differentiation to achieve optimal nephron endowment. Specifically, we will explore the roles of the homeobox gene sine oculis 2 (six2), and determine whether six2 is involved in the establishment of nephron number during kidney organogenesis. Using an RNAi methodology, experiments are designed to determine whether inactivation of six2 transcription early in nephrogenesis results in a significant decrease in ureteric bud growth and, therefore, nephron number in an organotypic kidney explant culture. Further, using a mouse model of heritable renal hypoplasia that lacks sufficient expression of six2 during development (the Brachyrrhine (Br) mutant mouse), we will take a systematic approach to re-introduce six2 to kidney explants that are prepared from Br mice and determine if exogenous six2 stimulates branching of the ureteric buds leading to an enhanced nephron production. Additionally, we will incorporate a 250 kb Bac containing six2 gene into the Br mouse genome to attempt to increase nephron number and, thereby rescuing the defective renal phenotype associated with six2 deficiency. Following the rescue we will assess if renal physiological features are restored in the adult Br mouse. This proposal will take advantage of the Br mouse strain that displays haploinsufficiency of six2 gene expression and is the only working colony in the world. Similarly, we have fully characterized the physiology of the adult Br mouse that demonstrates hypertension and chronic renal failure facilitating our phenotypic rescue experiments. When considered together, these experiments will provide the fundamental insights that constitute the genetic basis of six2 in renal morphogenesis and specifically establish whether six2 directly determines nephron endowment in the developing kidney. Results from this study will also underscore the importance of six2 in possible nephron restoration approaches in the adult diseased kidney.