Targeted mRNA Decay by RNA Binding Protein AUF1 Regulates Adult Muscle Stem Cell Fate, Promoting Skeletal Muscle Integrity.

Following skeletal muscle injury, muscle stem cells (satellite cells) are activated, proliferate, and differentiate to form myofibers. We show that mRNA-decay protein AUF1 regulates satellite cell function through targeted degradation of specific mRNAs containing 3' AU-rich elements (AREs). auf1(-/-) mice undergo accelerated skeletal muscle wasting with age and impaired skeletal muscle repair following injury. Satellite cell mRNA analysis and regeneration studies demonstrate that auf1(-/-) satellite cell self-renewal is impaired due to increased stability and overexpression of ARE-mRNAs, including cell-autonomous overexpression of matrix metalloprotease MMP9. Secreted MMP9 degrades the skeletal muscle matrix, preventing satellite-cell-mediated regeneration and return to quiescence. Blocking MMP9 activity in auf1(-/-) mice restores skeletal muscle repair and maintenance of the satellite cell population. Control of ARE-mRNA decay by AUF1 represents a mechanism for adult stem cell regulation and is implicated in human skeletal muscle wasting diseases.