Micro RNAs (miRNAs) have been shown to control many cellular processes including developmental timing in different organisms. The prediction that miRNAs are involved in regulating hox genes of flies and mouse is quite a recent idea and is supported by the finding that mir‐196 represses Hoxb8 gene expression. The non‐coding regions that encode these miRNAs are also conserved across species in the same way as other mechanisms that regulate expression of hox genes. On the contrary, until now no homeotic phenotype, (...) a hallmark of any hox gene mutation, had been associated with any hox miRNA. Recent work on bithorax complex miRNA (miR–iab‐4–5p) shows, for the first time, that miRNAs can lead to homeotic transformation. This miRNA regulates Ultrabithorax (Ubx) and results in the transformation of haltere to wing.1 This study unveils a new complexity and finesse to the regulation of hox gene expression pattern that is needed for determining the anteroposterior body axis in all bilaterians. BioEssays 28: 445–448, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Spatially and temporally restricted expression of Hox genes requires multiple mechanisms at both the transcriptional and the post-transcriptional levels. New insight into this precise expression mechanism comes from recent findings of a novel sense–antisense miRNA combination from the bithorax complex of Drosophila melanogaster.1-4 These two miRNAs encoded from the same locus target 3′ untranslated regions of anterior hox genes, Antp, Ubx and abd-A to establish the dominance of posterior hox gene Abd-B in its expression domain. Such double-edge tools, sense–antisense miRNA (...) combinations, also operate at multiple loci in the genome implicating their wider impact on the post-transcriptional gene regulation in eukaryotes. BioEssays 30:1058–1061, 2008. © 2008 Wiley Periodicals, Inc. (shrink)