An in vivo reporter of BMP signaling in organogenesis reveals targets in the developing kidney.
An in vivo reporter of BMP signaling in organogenesis reveals targets in the developing kidney.
复制标题
DOI：
10.1186/1471-213x-8-86
复制
发表时间：
2008-09-18
影响因子：
--
通讯作者：
Oxburgh L
中科院分区：
文献类型：
--
作者：
Blank U;Seto ML;Adams DC;Wojchowski DM;Karolak MJ;Oxburgh L
骨形态发生蛋白（BMPs）调节器官发生过程中的基本过程，对这些分泌蛋白的功能理解取决于对其靶细胞的鉴定。在这项研究中，我们为器官发生研究生成了一个转基因报告基因，我们用它来定义发育中的肾脏中BMP通路的激活。报告BMP通路激活的小鼠品系是在来自Id1的BMP响应元件的控制下，通过转基因表达β-半乳糖苷酶产生的。报告基因的表达与所研究的所有器官中通路激活的免疫测定相吻合，验证了该模型。使用这些报告器，我们已经生成了发育肾脏中BMP信号传导的细胞靶标的详细图谱。我们发现SMAD依赖的BMP信号在收集导管主干中是活跃的，而不是尖端。此外，肾小球内皮细胞和肾近端小管从肾囊期开始显示通路激活。令人惊讶的是，在肾脏肾源区检测到很少的激活，并且在器官培养中，BMP治疗无法激活肾元祖细胞中依赖SMAD的BMP信号。相反，信号传导是有效地诱导收集导管尖端。由BMP应答基因（如Id1）的控制元件驱动的转基因报告在BMP通路激活研究的敏感性和一致性方面比免疫染色具有显著优势。他们也提供了机会，分析BMP信号在器官和原代细胞培养受到实验操作。利用这样一个报告细胞，我们发现了一个惊人的发现：依赖于SMAD的BMP信号在肾元祖细胞中是不活跃的，并且这些细胞对生长因子的激活是不耐受的。此外，我们发现BMP通路在收集管尖端通常不活跃，但它可以被BMP处理异常激活，这可能解释了BMP处理对收集管生长和分支的抑制作用。
Bone morphogenetic proteins (BMPs) regulate essential processes during organogenesis, and a functional understanding of these secreted proteins depends on identification of their target cells. In this study, we generate a transgenic reporter for organogenesis studies that we use to define BMP pathway activation in the developing kidney. Mouse strains reporting on BMP pathway activation were generated by transgenically expressing β-galactosidase under the control of BMP responsive elements from Id1. Reporter expression corresponds well with immunoassays for pathway activation in all organs studied, validating the model. Using these reporters we have generated a detailed map of cellular targets of BMP signaling in the developing kidney. We find that SMAD dependent BMP signaling is active in collecting duct trunks, but not tips. Furthermore, glomerular endothelial cells, and proximal nephron tubules from the renal vesicle stage onward show pathway activation. Surprisingly, little activation is detected in the nephrogenic zone of the kidney, and in organ culture BMP treatment fails to activate SMAD dependent BMP signaling in nephron progenitor cells. In contrast, signaling is efficiently induced in collecting duct tips. Transgenic reporters driven by control elements from BMP responsive genes such as Id1 offer significant advantages in sensitivity and consistency over immunostaining for studies of BMP pathway activation. They also provide opportunities for analysis of BMP signaling in organ and primary cell cultures subjected to experimental manipulation. Using such a reporter, we made the surprising finding that SMAD dependent BMP signaling is inactive in nephron progenitors, and that these cells are refractory to activation by applied growth factors. Furthermore, we find that the BMP pathway is not normally active in collecting duct tips, but that it can be ectopically activated by BMP treatment, offering a possible explanation for the inhibitory effects of BMP treatment on collecting duct growth and branching.