Regulation of DLK1 by the maternally expressed miR-379/miR-544 cluster may underlie callipyge polar overdominance inheritance.

Inheritance of the callipyge phenotype in sheep is an example of polar overdominance inheritance, an unusual mode of inheritance. To investigate the underlying molecular mechanism, we profiled the expression of the genes located in the Delta-like 1 homolog (Dlk1)-type III iodothyronine deiodinase (Dio3) imprinting region in mice. We found that the transcripts of the microRNA (miR) 379/miR-544 cluster were highly expressed in neonatal muscle and paralleled the expression of the Dlk1.

Transcriptional regulatory circuits controlling muscle fiber type switching.

Skeletal muscle fitness plays vital roles in human health and disease and is determined by developmental as well as physiological inputs. These inputs control and coordinate muscle fiber programs, including capacity for fuel burning, mitochondrial ATP production, and contraction. Recent studies have demonstrated crucial roles for nuclear receptors and their co-activators, and microRNAs (miRNAs) in the regulation of skeletal muscle energy metabolism and fiber type determination.