Identification and characterization of a novel Muscle Lamin A/C (LMNA) Interacting Protein (MLIP): A regulator of Pax7

Abstract

Specific missense mutations LMNA have been identified to be associated with muscular dystrophy suggesting that LMNA interacts with a muscle specific factor(s). A yeast two‐hybrid screen with LMNA as bait was employed to identify muscle specific proteins. A previously uncharacterized cDNA clone was identified that interacts with LMNA in muscle, MLIP. Preliminary results show MLIP protein is primarily expressed in brain, heart and skeletal muscle. No structural or functional domains have been identified within MLIP.Objective: To define the function of MLIP in muscle.Results: MLIP is expressed endogenously in a mouse myoblast cell line (C2C12) and is co‐localized to the nuclear envelope and PML bodies. Initiation of C2C12 differentiation led to a 3‐fold increase in MLIP expression peaking at 24hrs and MLIP continued to be expressed in differentiated myotubes. Specific knockdown of MLIP in C2C12 cells by shRNAi led to significant (p<0.01) reduction in Pax7 expression with a concurrent reduction in Myf5, MyoD and myogenin with Pax3 expression being unaffected. To determine whether MLIP is necessary and/or sufficient for myogenic differentiation, stable C2C12 cell lines are being generated that either knockdown MLIP or over‐express MLIP.Conclusion: MLIP is a novel LMNA interacting protein that may regulate Pax7 a myogenic determinant during regenerative myogenesis. Funding: CIHR operating grant to PGB.