Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0693, USA.
Development. 2009 Dec;136(24):4213-24. doi: 10.1242/dev.037580.
Ureteric bud (UB) emergence from the Wolffian duct (WD), the initiating step in metanephric kidney morphogenesis, is dependent on GDNF; however, GDNF by itself is generally insufficient to induce robust budding of the isolated WD in culture. Thus, additional factors, presumably peptides or polypeptide growth factors, might be involved. Microarray data from in vivo budding and non-budding conditions were analyzed using non-negative matrix factorization followed by gene ontology filtering and network analysis to identify sets of genes that are highly regulated during budding. These included the GDNF co-receptors GFRalpha1 and RET, as well as neuropeptide Y (NPY). By using ANOVA with pattern matching, NPY was also found to correlate most significantly to the budded condition with a high degree of connectedness to genes with developmental roles. Exogenous NPY [as well as its homolog, peptide YY (PYY)] augmented GDNF-dependent budding in the isolated WD culture; conversely, inhibition of NPY signaling or perturbation of NPY expression inhibited budding, confirming that NPY facilitates this process. NPY was also found to reverse the decreased budding, the downregulation of RET expression, the mislocalization of GFRalpha1, and the inhibition of AKT phosphorylation that resulted from the addition of BMP4 to the isolated WD cultures, suggesting that NPY acts through the budding pathway and is reciprocally regulated by GDNF and BMP4. Thus, the outgrowth of the UB from the WD might result from a combination of the upregulation of the GDNF receptors together with genes that support GDNF signaling in a feed-forward loop and/or counteraction of the inhibitory pathway regulated by BMP4.
输尿管芽（UB）从沃夫氏管（WD）中出现，这是肾发生的起始步骤，依赖于 GDNF；然而，GDNF 本身通常不足以诱导 WD 在培养中产生强烈的芽状。因此，可能涉及其他因素，推测是肽或多肽生长因子。使用非负矩阵分解对体内出芽和不出芽条件的微阵列数据进行分析，然后进行基因本体过滤和网络分析，以识别在出芽过程中高度调控的基因集。这些基因包括 GDNF 共受体 GFRalpha1 和 RET，以及神经肽 Y（NPY）。通过使用具有模式匹配的 ANOVA，还发现 NPY 与出芽条件的相关性最显著，与具有发育作用的基因的连接程度很高。外源性 NPY [以及其同源物，肽 YY（PYY）] 增强了 WD 培养物中 GDNF 依赖性出芽；相反，抑制 NPY 信号或干扰 NPY 表达抑制了出芽，证实了 NPY 促进了这一过程。还发现 NPY 逆转了 WD 培养物中 BMP4 添加导致的出芽减少、RET 表达下调、GFRalpha1 定位错误以及 AKT 磷酸化抑制，表明 NPY 通过出芽途径发挥作用，并受到 GDNF 和 BMP4 的反向调节。因此，UB 从 WD 的延伸可能是 GDNF 受体的上调与支持 GDNF 信号的基因的组合的结果，这些基因在正反馈回路中发挥作用，和/或对抗由 BMP4 调节的抑制途径。
