Functions of miR-1 and miR-133a during the postnatal development of masseter and gastrocnemius muscles.

The present study investigated the function of miR-1 and miR-133a during the postnatal development of mouse skeletal muscles. The amounts of miR-1 and miR-133a were measured in mouse masseter and gastrocnemius muscles between 1 and 12 weeks after birth with real-time polymerase chain reaction and those of HDACs, MEF2, MyoD family, MCK, SRF, and Cyclin D1 were measured at 2 and 12 weeks with Western blotting. In both the masseter and gastrocnemius muscles, the amount of miR-1 increased between 1 and 12 weeks, whereas the amount of HADC4 decreased between 2 and 12 weeks. In the masseter muscle, those of MEF2, MyoD, Myogenin, and MCK increased between 2 and 12 weeks, whereas, in the gastrocnemius muscle, only those of MRF4 and MCK increased. The extent of these changes in the masseter muscle was greater than that in the gastrocnemius muscle. The amounts of miR-133a, SRF, and Cyclin D1 did not change significantly in the masseter muscle between 1 and 12 weeks after birth. By contrast, in the gastrocnemius muscle, the amounts of miR-133a and Cyclin D1 increased, whereas that of SRF decreased. Our findings suggest that the regulatory pathway of miR-1 via HDAC4 and MEF2 plays a more prominent role during postnatal development in the masseter muscle than in the gastrocnemius muscle, whereas that of miR-133a via SRF plays a more prominent role in the gastrocnemius muscle than in the masseter muscle.