Mice with targeted inactivation of nBmp2 exhibit increased daytime activity

Abstract

Bone morphogenetic protein 2 (Bmp2) is a secreted signaling protein known to induce bone and cartilage formation, and has been implicated in several disease and developmental processes. Recently, a nuclear form of Bmp2 (nBmp2) was discovered in our lab. To determine the function of nBmp2, mice have been engineered in which the conventional secreted form of Bmp2 is produced normally, but nBmp2 cannot be translocated to the nucleus. Previous studies, including flexed arm‐hang strength tests, swim tests, and gait analysis, have been performed on the mutant and wild type mice and have revealed that mutant mice have significantly reduced strength. The objective of the current study was to characterize the running patterns in the mutant. Age‐matched wild type and mutant mice were allowed to run voluntarily on running wheels in their cages, and the distance covered was recorded at 30 minute intervals using the Lafayette Instrument Activity Wheel System. The results revealed little difference in total distance run during nighttime cycles, but male mutant mice ran approximately twice as much during the daytime as wild type mice. In addition, western blot analyses of muscle tissue from the WT and mutant males showed more cytochrome C in mutants. These results suggest that nBmp2 may play a role in regulating locomotor activity patterns by affecting muscle function. Supported by NIH grant AR48839 and by the Fulton Family Foundation.