title: Myostatin down-regulates the IGF-2 expression via ALK-Smad signaling during myogenesis in cattle.
abstract: Myostatin (MSTN) is a negative regulator during muscle differentiation, whereas insulin-like growth factors (IGFs) are essential for muscle development. MSTN and IGFs act oppositely during myogenesis, but there is little information on the mutual relationship of MSTN and IGFs. The present study was conducted to examine whether MSTN affects IGF expression during early myogenesis in cattle. IGF-1 mRNA was similarly expressed in M. longissimus thoracis of double-muscled (DM) and normal (NM) Japanese shorthorn cattle. IGF-2 mRNA expression was consistently higher in the normal and regenerating muscle of DM cattle than those of NM cattle. When myoblasts were isolated from regenerating M. longissimus thoracis, IGF-2 mRNA expression showed a significant increase in differentiating DM derived myoblasts (DM-myoblasts) as compared with differentiating NM derived myoblasts (NM-myoblasts). An addition of recombinant mouse myostatin (rMSTN) to myoblast cultures attenuated IGF-2 mRNA expression and decreased myotube formation, but did not effect IGF-1 mRNA expression. An activin-like kinase (ALK) inhibitor, SB431542, mediates MSTN action, suppressed the translocation of Smad2/3 into the nucleus in DM-myoblasts, and restored the attenuated IGF-2 mRNA expression and the decreased myotube formation induced by rMSTN in myoblast cultures. The findings indicate that MSTN may negatively regulate myoblast differentiation by suppressing IGF-2 expression via ALK-Smad signaling.
authors.affiliation: Department of Animal Biology, Graduate School of Agricultural Science, Tohoku University, Aoba, Sendai, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Miyake
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Hayashi
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Taketa
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Iwasaki
authors.forename: Kouichi
authors.initials: K
authors.lastname: Watanabe
authors.forename: Shyuich
authors.initials: S
authors.lastname: Ohwada
authors.forename: Hisashi
authors.initials: H
authors.lastname: Aso
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamaguchi
mesh_terms: D029404:Activin Receptors / Q000378:metabolism*; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D015536:Down-Regulation; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D024510:Muscle Development / Q000187:drug effects*; D055435:Myostatin / Q000494:pharmacology*; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*
chemical_list: D055435:Myostatin; D051785:Smad Proteins; D007335:Insulin-Like Growth Factor II; D029404:Activin Receptors