ROLE OF micro-RNAs IN THE REGULATION OF GENE EXPRESSION

First miRNAs were described in a flatworm species C. elegans, which led to an understanding of their important regulatory role in cell differentiation (Lee et al., 1993; Wightmanet al., 1993). Another critical step was the discovery of the second miRNA named let-7, which is a product of expression of a heterochronic switch gene in C. elegans (Reinhart et al., 2000). Loss of let-7 gene activity causes reiteration of larval cell fates during the adult stage, whereas increased let-7 gene dosage causes precocious expression of adult fates during larval stages. Let7 gene encodes a temporally regulated ROLE OF micro-RNAs IN THE REGULATION OF GENE EXPRESSION