Mechanisms of Veterbrate Dorsal-ventral Limb Patterning

描述（申请人提供）：详细了解发育机制对于诊断和治疗先天性畸形至关重要。一组常见的先天性畸形是影响肢体发育的畸形。我们已经确定了一种这样的畸形的潜在原因，指甲-髌骨综合征（NPS），影响指甲，髌骨和肘关节的发育。NPS是由lim同源结构域转录因子LMX1B突变引起的。我们在小鼠身上的研究表明，Imxlb在背肢芽间质中特异性表达，在那里它作为一个选择基因指定背细胞的命运。Imxlb的表达如何局限于并维持在背肢芽间质中，以及Imxlb调节背-腹侧模式的机制尚不清楚。在拟议的研究中，我们将解决三个主要问题。首先，我们将采用Imx1 b的条件基因靶向来确定间充质组织的特定亚群是否协调肢体的肌肉骨骼模式。其次，我们将通过谱系追踪和转基因分析来研究Imxlb背侧特异性表达的机制。最后，我们将测试ephrin/Eph信号通路作为Imxlb调节肢体背腹侧芽发育的候选效应体。综上所述，这些实验将为脊椎动物选择基因如何协调调节复杂的发育程序提供重要的见解。在发育和成人过程中，身体的其他组织也需要Lmxlb活性。从对小鼠和人类的研究中，我们知道Imx1 b对于肾脏和眼睛流出道的正常功能以及CMS的多巴胺能和血清素能系统的正常发育是必需的。这项拟议的研究将提供有关Imxlb在肢体发育中的功能的信息，但也将阐明Imxlb如何调节肾脏、眼睛和大脑的发育。由于携带LMX1B突变的个体有肾衰竭和青光眼的风险，我们的研究也将影响重要的健康问题。

DESCRIPTION (provided by applicant): Detailed understanding of developmental mechanisms is essential to diagnose and treat congenital malformations. A common group of congenital malformations are those that affect limb development. We have defined underlying cause of one such malformation, nail-patella syndrome (NPS) that affects the development of the nails, patella, and elbow. NPS is caused by mutations in the LIM-homeodomain transcription factor LMX1B. Our studies in the mouse have indicated that Imxlb is expressed specifically in the dorsal limb bud mesenchyme where it acts as a selector gene to specify dorsal cell fates. How Imxlb expression is restricted to and maintained in the dorsal limb bud mesenchyme is poorly understood as is the mechanism(s) by which Imxlb regulates dorsal-ventral patterning. In the proposed research we will address three main issues. First, we will employ conditional gene targeting of Imx1 b to determine whether specific subsets of mesenchymal tissues coordinate musculoskeletal patterning of the limb. Second, we will examine mechanisms that are responsible for the dorsal-specific expression of Imxlb by lineage tracing and transgenic analysis. Finally, we will test the ephrin/Eph signaling pathway as a candidate effector of Imxlb in regulating dorsal-ventral limb bud development. Taken together, these experiments will provide significant insight into how vertebrate selector genes function to coordinate regulation of a complex developmental program. Lmxlb activity is also required in other tissues of the body both during development and in the adult. From studies in mice and humans we know that Imx1 b is required for proper functioning of the kidney and outflow tract of the eye as well as for proper development of the dopaminergic and serotonergic systems of the CMS. The proposed research will provide information about the function of Imxlb in limb development, but will also shed light into how Imxlb regulates kidney, eye, and brain development. As individuals with mutations in LMX1B are at risk for renal failure and glaucoma our research will also impact important heath concerns.