Downregulation of the Host Gene jigr1 by miR-92 Is Essential for Neuroblast Self-Renewal in Drosophila

Intragenic micrornas (mirnas),located mostly in the introns of protein-coding genes,are often co-expressed with their host mrnas. however,their functional interaction in development is largely unknown. here we show that in drosophila,mir-92a and mir-92b are embedded in the intron and 3’utr of jigr1,respectively,and co-expressed with some jigr1 isoforms. mir-92a and mir-92b are highly expressed in neuroblasts of larval brain where jigr1 expression is low. genetic deletion of both mir-92a and mir-92b demonstrates an essential cell-autonomous role for these mirnas in maintaining neuroblast self-renewal through inhibiting premature differentiation. we also show that mir-92a and mir-92b directly target jigr1 in vivo and that some phenotypes due to the absence of these mirnas are partially rescued by reducing the level of jigr1. these results reveal a novel function of the mir-92 family in drosophila neuroblasts and provide another example that local negative feedback regulation of host genes by intragenic mirnas is essential for animal development. © 2015 yuva-aydemir et al.