Rb1cc1 is critical for myoblast differentiation through Rb1 regulation.

Rb1-inducible coiled-coil 1 (Rb1cc1) expressed at high levels is associated with the maturation of human embryonic musculoskeletal cells. To clarify the molecular role of Rb1cc1 in muscular differentiation, we investigated the expression of Rb1cc1 and other genes that regulate differentiation in murine embryonic tissues and in C2C12 myoblasts. We also evaluated the effects of RNA interference (RNAi)-mediated Rb1cc1 knockdown on C2C12 myoblast differentiation. After Rb1cc1, Rb1 and myosin heavy chain (Myhc) were expressed in mouse embryonic muscles. The synchronous expression of Rb1cc1 and Rb1 predicted Myhc expression during C2C12 myoblast differentiation. RNAi-mediated knockdown of Rb1cc1 led to Rb1 suppression, and C2C12 myoblasts failed to differentiate. These results indicated that Rb1cc1 is a potent regulator of the Rb1 pathway and a novel mediator that plays a crucial role in muscular differentiation. Rb1cc1 expression is, thus, a prerequisite for myogenic differentiation.