Genetics

Mighty Meaty miRNAs

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Science  16 Jun 2006:
Vol. 312, Issue 5780, pp. 1574-1575
DOI: 10.1126/science.312.5780.1574d

The Texel breed of sheep sports a pronounced musculature, which makes it economically important for the agricultural industry. To establish the basis of the Texel phenotype, Clop et al. have used quantitative genetics to map the genomic region responsible, initially to the second chromosome and then, using finer quantitative trait loci mapping, to the myostatin gene; mutations in this gene are known to increase muscle mass in mice and humans. Of the 20 single-nucleotide polymorphisms identified, two track the Texel phenotype closely. One of these is located in the 3' untranslated sequence of the myostatin gene. The G-to-A change creates an octamer sequence that inadvertently corresponds to the seed, a critical specificity determinant, of the micro (mi) RNAs miR-1 and miR-206, both of which are expressed at high levels in sheep muscle. Analysis of myostatin levels revealed a marked reduction in Texel sheep and is consistent with the role of miRNAs in repressing the translation of target genes. In a bioinformatic analysis of the human and mouse genomes, the authors locate hundreds of polymorphisms that have the potential to create or destroy targets of miRNA seed sequences, and hence to influence gene expression in a fashion analogous to that seen in sheep. — GR

Nat. Genet. 10.1038/ng1810 (2006).

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