Embryology Research Today is a free monthly online journal that collates and summarizes the latest research about Embryology, including details on stem cells, reproduction, transplants, cloning.

Spatial regulation of microRNA gene expression in the Drosophila embryo.

Biemar F, Zinzen R, Ronshaugen M, Sementchenko V, Manak JR, Levine MS

Division of Genetics and Development, Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, CA 94720, USA.

MicroRNAs (miRNAs) regulate posttranscriptional gene activity by binding to specific sequences in the 3' UTRs of target mRNAs. A number of metazoan miRNAs have been shown to exhibit tissue-specific patterns of expression. Here, we investigate the possibility that localized expression is mediated by tissue-specific enhancers, comparable to those seen for protein-coding genes. Two miRNA loci in Drosophila melanogaster are investigated, the mir-309-6 polycistron (8-miR) and the mir-1 gene. The 8-miR locus contains a cluster of eight distinct miRNAs that are transcribed in a common precursor RNA. The 8-miR primary transcript displays a dynamic pattern of expression in early embryos, including repression at the anterior and posterior poles. An 800-bp 5' enhancer was identified that recapitulates this complex pattern when attached to a RNA polymerase II core promoter fused to a lacZ-reporter gene. The miR-1 locus is specifically expressed in the mesoderm of gastrulating embryos. Bioinformatics methods were used to identify a mesoderm-specific enhancer located approximately 5 kb 5' of the miR-1 transcription unit. Evidence is presented that the 8-miR enhancer is regulated by the localized Huckebein repressor, whereas miR-1 is activated by Dorsal and Twist. These results provide evidence that restricted activities of the 8-miR and miR-1 miRNAs are mediated by classical tissue-specific enhancers.

Published 2 November 2005 in Proc Natl Acad Sci U S A, 102(44): 15907-11.
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