A ribosomal DNA-hosted microRNA regulates zebrafish embryonic angiogenesis.

MicroRNAs (miRNAs) are single-stranded small non-coding RNAs, generally 18-25 nucleotides in length, that act as repressors of gene expression. miRNAs are encoded by independent genes or processed from a variety of different RNA species. So far, there is no evidence showing that the ribosomal DNA-hosted microRNA is implicated in vertebrate development. Currently, we found a highly expressed small RNA hosted in ribosomal DNA was predicted as a novel miRNA, named miR-ntu1, in zebrafish endothelial cells by deep sequencing analysis. The miRNA was validated by custom-designed Taqman PCR, Northern Blot, and in silico analysis. Furthermore, we demonstrated that miR-ntu1 played a crucial role in zebrafish angiogenesis via modulation of Notch signaling. Our findings provide a notable case that a miRNA hosted in ribosomal DNA is involved in vertebrate development.