Ureteric Bud Patterning

摘要 哺乳动物肾脏的发育依赖于输尿管芽。它的近端 在发育中的肾脏中诱导肾单位形成并经历分支 形态发生形成肾内集合系统，而其远端或主干 域分化为输尿管。输尿管芽调节异常 形态发生可导致一系列先天性缺陷，最常见的是 输尿管重复和梗阻。然而组织间的相互作用和信号传递 限制输尿管数量和控制输尿管平滑肌分化的途径 对于尿液不受阻碍地流向膀胱所需的功能仍然知之甚少。 该建议的重点是输尿管形态发生。在目标1中，Bmp信号传导的作用 限制输尿管芽生长到沿着泌尿道的单一部位， 控制输尿管平滑肌分化将在患有严重的输尿管狭窄的小鼠中进行分析。 Bmp 4基因剂量的敲低，支持胚胎存活至出生，但不 超越。可诱导的Bmp 4敲低将使用Cre-lox技术完成， 现有的鼠标线。BMP 4将在不同的发展阶段被淘汰， 分析该信号因子在调节输尿管数量中的作用，从其 控制终末输尿管分化的作用。在目标2中，我们将分析鼠标线 缺乏Pbx 1（一种hox基因辅因子）的表达。我们发现Pbx 1是 对限制Bmp 4信号传导和输尿管平滑肌形成至关重要。 该突变株系将用于剖析遗传途径和细胞类型， 控制肾脏和肾脏交界处平滑肌的组织 输尿管是新生儿尿路梗阻最常见的部位。成功 这些实验的完成将有助于深入了解输尿管的易感性 形态发生到先天性缺陷。

ABSTRACT Mammalian renal development is dependent on the ureteric bud. Its proximal tip induces nephron formation in the developing kidney and undergoes branching morphogenesis forming the intra-renal collecting system whereas its distal or trunk domain differentiates into the ureter. Abnormal regulation of ureteric bud morphogenesis can result in a spectrum of congenital defects, the most common being ureteral duplications and obstructions. Yet the tissue interactions and signaling pathways that limit ureter number and control ureteral smooth muscle differentiation required for the un-obstructed flow of urine to the bladder remain poorly understood. This proposal is focused on ureter morphogenesis. In Aim 1, the role of Bmp signaling in restricting ureteric bud outgrowth to a single site along the urinary tract and in controlling ureteral smooth muscle differentiation will be analyzed in mice with a severe knockdown in Bmp4 gene dosage that supports embryonic viability to birth, but not beyond. Inducible Bmp4 knockdown will be accomplished using Cre-lox technology and existing mouse lines. Bmp4 will be knocked down at different stages of development to analyze the role of this signaling factor in regulating ureter number separately, from its role in controlling terminal ureter differentiation. In Aim 2, we will analyze a mouse line lacking expression of Pbx1, a hox gene cofactor. We have discovered that Pbx1 is essential for restricting Bmp4 signaling and smooth muscle formation to the ureter. This mutant line will be used to dissect the genetic pathways and cell type (s) that control the organization of smooth muscle at the border between the kidney and the ureter, the most common site of urinary tract obstructions in newborns. The successful completion of these experiments will provide insight into the susceptibility of ureter morphogenesis to congenital defects.