Div. of Nephrology, Dept. of Pediatrics, Children's Hospital of Pittsburgh of UPMC, Rangos Research Center, 4401 Penn Ave., Pittsburgh, PA 15224.
Am J Physiol Renal Physiol. 2014 Apr 1;306(7):F764-72. doi: 10.1152/ajprenal.00426.2013. Epub 2014 Feb 5.
MicroRNAs (miRNAs) are small, noncoding regulatory RNAs that act as posttranscriptional repressors by binding to the 3'-untranslated region (3'-UTR) of target genes. They require processing by Dicer, an RNase III enzyme, to become mature regulatory RNAs. Previous work from our laboratory revealed critical roles for miRNAs in nephron progenitors at midgestation (Ho J, Pandey P, Schatton T, Sims-Lucas S, Khalid M, Frank MH, Hartwig S, Kreidberg JA. J Am Soc Nephrol 22: 1053-1063, 2011). To interrogate roles for miRNAs in the early metanephric mesenchyme, which gives rise to nephron progenitors as well as the renal stroma during kidney development, we conditionally ablated Dicer function in this lineage. Despite normal ureteric bud outgrowth and condensation of the metanephric mesenchyme to form nephron progenitors, early loss of miRNAs in the metanephric mesenchyme resulted in severe renal dysgenesis. Nephron progenitors are initially correctly specified in the mutant kidneys, with normal expression of several transcription factors known to be critical in progenitors, including Six2, Pax2, Sall1, and Wt1. However, there is premature loss of the nephron progenitor marker Cited1, marked apoptosis, and increased expression of the proapoptotic protein Bim shortly after the initial inductive events in early kidney development. Subsequently, there is a failure in ureteric bud branching and nephron progenitor differentiation. Taken together, our data demonstrate a previously undetermined requirement for miRNAs during early kidney organogenesis and indicate a crucial role for miRNAs in regulating the survival of this lineage.
微小 RNA（miRNAs）是一种小的非编码调控 RNA，通过与靶基因的 3'-非翻译区（3'-UTR）结合，作为转录后抑制剂发挥作用。它们需要 Dicer，一种 RNase III 酶的加工，才能成为成熟的调控 RNA。我们实验室的先前工作表明，miRNAs 在中孕期的肾祖细胞中发挥着关键作用（Ho J、Pandey P、Schatton T、Sims-Lucas S、Khalid M、Frank MH、Hartwig S、Kreidberg JA. J Am Soc Nephrol 22: 1053-1063, 2011）。为了研究 miRNA 在早期生肾中胚层中的作用，该中胚层既能产生肾祖细胞，也能在肾脏发育过程中产生肾间质，我们在这个谱系中条件性地缺失了 Dicer 功能。尽管输尿管芽的生长和生肾中胚层的浓缩都正常，形成肾祖细胞，但早期生肾中胚层中 miRNA 的缺失导致严重的肾发育不良。在突变肾脏中，肾祖细胞最初被正确指定，几个已知对祖细胞至关重要的转录因子的表达正常，包括 Six2、Pax2、Sall1 和 Wt1。然而，Cited1 这个肾祖细胞标志物的过早丢失、明显的细胞凋亡以及促凋亡蛋白 Bim 的表达增加，在早期肾脏发育的初始诱导事件后不久就出现了。随后，输尿管芽分支和肾祖细胞分化失败。总之，我们的数据表明，miRNAs 在早期肾脏器官发生过程中存在以前未确定的需求，并表明 miRNAs 在调节这个谱系的存活方面起着至关重要的作用。
