Regulation of kidney field specification by transcriptional regulation of microRNAs

The transcriptional events driving specification of the kidney field have been well characterized. However, it remains unknown how the initial field size is established, patterned, and proportioned. Lhx1 is a transcription factor expressed in the kidney anlage and is required for specification of the kidney field, but few Lhx1 interacting cofactors or downstream targets have been identified. By tandem-affinity purification, we isolated Furry (FRY), a multifunctional protein that acts as a transcriptional co-repressor of microRNAs. We found that Xenopus embryos depleted of fry exhibit loss of the kidney field, phenocopying the lhx1 depleted animals. In addition, we demonstrated a synergism between Fry and Lhx1, identified candidate microRNAs regulated by the protein pair, and show at least two microRNA clusters influence specification of the kidney field. Therefore, our data shows that a tissue-specific transcription factor, Lhx1, can interact with a broadly expressed microRNA repressor, Fry, to establish the kidney field. miRNA Deep sequencing of 3 Xenopus laevis samples

调控肾脏域（kidney field）特化的转录事件已得到充分表征。然而，目前仍不清楚初始肾脏域的大小是如何确立、模式化并实现比例调控的。Lhx1是一种在肾脏原基（kidney anlage）中表达的转录因子，对肾脏域的特化必不可少，但目前已被鉴定的与Lhx1互作的辅因子及其下游靶标寥寥无几。通过串联亲和纯化（tandem-affinity purification）技术，我们分离得到了Furry（FRY）——一种可作为微小RNA（microRNA）转录共抑制因子的多功能蛋白。我们发现，敲低fry的非洲爪蟾（Xenopus laevis）胚胎会出现肾脏域缺失的表型，该表型与lhx1敲低的动物完全一致。此外，我们证实了Furry与Lhx1之间存在协同作用，鉴定出了受该蛋白对调控的候选微小RNA，并证明至少有两个微小RNA簇参与调控肾脏域的特化过程。综上，本研究数据表明，组织特异性转录因子Lhx1可与广泛表达的微小RNA抑制因子Furry相互作用，共同确立肾脏域。3份非洲爪蟾（Xenopus laevis）样本的微小RNA深度测序