Structural and Dynamic Characterization of the C313Y Mutation in Myostatin Dimeric Protein, Responsible for the "Double Muscle" Phenotype in Piedmontese Cattle.

Silvia Bongiorni,Alessio Valentini,Giovanni Chillemi

doi:10.3389/fgene.2016.00014

Abstract

The knowledge of the molecular effects of the C313Y mutation, responsible for the “double muscle” phenotype in Piedmontese cattle, can help understanding the actual mechanism of phenotype determination and paves the route for a better modulation of the positive effects of this economic important phenotype in the beef industry, while minimizing the negative side effects, now inevitably intersected. The structure and dynamic behavior of the active dimeric form of Myostatin in cattle was analyzed by means of three state-of-the-art Molecular Dynamics simulations, 200-ns long, of wild-type and C313Y mutants. Our results highlight a role for the conserved Arg333 in establishing a network of short and long range interactions between the two monomers in the wild-type protein that is destroyed upon the C313Y mutation even in a single monomer. Furthermore, the native protein shows an asymmetry in residue fluctuation that is absent in the double monomer mutant. Time window analysis on further 200-ns of simulation demonstrates that this is a characteristic behavior of the protein, likely dependent on long range communications between monomers. The same behavior, in fact, has already been observed in other mutated dimers. Finally, the mutation does not produce alterations in the secondary structure elements that compose the characteristic TGF-β cystine-knot motif.

Highlights

Myostatin (MSTN), named growth differentiation factor-8, is a member of the transforming growth factor-beta (TGF-beta) superfamily and is the primary negative regulator of skeletal muscle development (Beyer et al, 2013)
Myostatin signaling acts through the activin receptor type IIA (ActRIIA) or ActR-IIB and either TβRI/ALK-5 or ALK4, type I receptors on skeletal muscle, triggering the activation of TGF-β–specific Smads, Smad2 and Smad3 followed by oligomerization with Smad4 (Massagué and Wotton, 2000)
The structural and dynamic effect of the C313Y mutation on the MSTN protein has been investigated in the dimeric form, i.e., the functional state of MSTN, with the following models: (1) the wildtype form (0-copy); the heterodimer composed by the monomer in mutated form and the second in wild-type one (1-copy); (2) the homodimer mutant (2-copy)

Summary

Introduction

Myostatin (MSTN), named growth differentiation factor-8, is a member of the transforming growth factor-beta (TGF-beta) superfamily and is the primary negative regulator of skeletal muscle development (Beyer et al, 2013). Double Muscle Mutation in Myostatin bonds between cysteines 272–282; 281–340; 309–372; and 313– 374 These nine highly conserved cysteine residues are typical of the members of the TGF-β superfamily (McPherron et al, 1997), and together with the inter-chain disulfide bond form the characteristic TGF-β cystine-knot structural motif. The Smad protein complex translocates into the nucleus, where it regulates transcription of specific myogenic regulatory genes such as Myod (Langley et al, 2002). Inhibition of this pathway results in muscle hyperplasia (Lee and McPherron, 2001; Lee, 2007). Antagonists of MSTN activity such as the follistatin which hinders access to signaling receptors on skeletal muscle (Sumitomo et al, 1995), are considered as potential therapeutics in the treatment of muscle-wasting disorders such as muscular dystrophy and sarcopenia (Bogdanovich et al, 2002, 2005)

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Conclusion