Noncoding RNAs (ncRNAs) play increasingly appreciated gene-regulatory roles. 
Here, we describe a regulatory network centered on four ncRNAs-a long ncRNA, a 
circular RNA, and two microRNAs-using gene editing in mice to probe the 
molecular consequences of disrupting key components of this network. The long 
ncRNA Cyrano uses an extensively paired site to miR-7 to trigger destruction of 
this microRNA. Cyrano-directed miR-7 degradation is much more effective than 
previously described examples of target-directed microRNA degradation, which 
come primarily from studies of artificial and viral RNAs. By reducing miR-7 
levels, Cyrano prevents repression of miR-7-targeted mRNAs and enables 
accumulation of Cdr1as, a circular RNA known to regulate neuronal activity. 
Without Cyrano, excess miR-7 causes cytoplasmic destruction of Cdr1as in 
neurons, in part through enhanced slicing of Cdr1as by a second miRNA, miR-671. 
Thus, several types of ncRNAs can collaborate to establish a sophisticated 
regulatory network.