Abstract

MicroRNAs (miRNAs) are a large class of short non-coding RNAs found in many plants and animals, where they often act as post-transcriptional repressors of gene expression. Here we report the generation and analysis of loss-of-function mutations in almost all known microRNA genes in C. elegans. Although we identify possible new roles for microRNAs in C. elegans embryogenesis and larval development, we find that the majority of microRNAs are not essential for development or viability of C. elegans. Moreover, whole microRNA families are not required for viability. This study represents the first comprehensive analysis of microRNA function in any organism and provides a unique resource for the study of microRNAs.