Report Many Families of C. elegans MicroRNAs Are Not Essential for Development or Viability

Summary MicroRNAs (miRNAs) are approximately 23 nt regulatory RNAs that posttranscriptionally inhibit the functions of protein-coding mRNAs. We previously found that most C. elegans miRNAs are individually not essential for development or viability and proposed that paralogous miRNAs might often function redundantly Results and Discussion Genetic, computational, and genome-wide expression analyses indicate that microRNAs (miRNAs) function primarily by targeting sites in the 3 0 -untranslated regions (UTRs) of their target genes To investigate functional redundancy among miRNA family members, we constructed double, triple, or quadruple multiply mutant strains that each carried mutations in members of a given family for 15 of the 23 known C. elegans miRNA families The mir-35 family comprises eight miRNAs, mir-35 through mir-42, located in two genomic miRNA clusters separated by 350 kb on LGII. One cluster contains mir-35 through mir-41 (mir-35-41), and the other contains mir-42, mir-43, and mir-44 (mir-42-44) ( We obtained three deletions that affect mir-35 family members in the mir-35-41 or mir-42-44 clusters and constructed strains lacking most or all mir-35 family members ( The mir-35 family contains members that are tightly clustered in the genome, and the deletions we isolated affected all or multiple members of each cluster ( We examined the mir-35 family mutant phenotype in more detail. Most animals deleted for all mir-35 family members underwent developmental arrest at the two-fold or three-fol