Limits...
Netrins and neogenin promote myotube formation.

Kang JS, Yi MJ, Zhang W, Feinleib JL, Cole F, Krauss RS - J. Cell Biol. (2004)

Bottom Line: These proteins stimulate myotube formation and enhance myogenic bHLH- and NFAT-dependent transcription.Furthermore, neogenin binds to CDO in a cis fashion, and myoblasts lacking CDO are defective in responding to recombinant netrin.It is proposed that netrin-3 and neogenin may promote myogenic differentiation by an autocrine mechanism as components of a higher order complex of several promyogenic cell surface proteins.

View Article: PubMed Central - PubMed

Affiliation: Brookdale Department of Molecular, Cell and Developmental Biology, Mount Sinai School of Medicine, New York, NY 10029, USA.

ABSTRACT
Differentiation of skeletal myoblasts into multinucleated myotubes is a multistep process orchestrated by several families of transcription factors, including myogenic bHLH and NFAT proteins. The activities of these factors and formation of myotubes are regulated by signal transduction pathways, but few extracellular factors that might initiate such signals have been identified. One exception is a cell surface complex containing promyogenic Ig superfamily members (CDO and BOC) and cadherins. Netrins and their receptors are established regulators of axon guidance, but little is known of their function outside the nervous system. We report here that myoblasts express the secreted factor netrin-3 and its receptor, neogenin. These proteins stimulate myotube formation and enhance myogenic bHLH- and NFAT-dependent transcription. Furthermore, neogenin binds to CDO in a cis fashion, and myoblasts lacking CDO are defective in responding to recombinant netrin. It is proposed that netrin-3 and neogenin may promote myogenic differentiation by an autocrine mechanism as components of a higher order complex of several promyogenic cell surface proteins.

Show MeSH
CDO is required for netrin-2 to produce the activated form of NFATc3. (A) Western blot analysis of neogenin, CDO, netrin-3, and MyoD in primary myoblasts isolated from wild-type (+/+) and Cdo−/− (−/−) mice. (B) Western blot analysis of NFATc3 in primary myoblasts of the indicated Cdo genotype treated with or without netrin-2 for 3 h. The top and bottom arrows indicate the presumptive phosphorylated and dephosphorylated forms of NFATc3, respectively.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172498&req=5

fig8: CDO is required for netrin-2 to produce the activated form of NFATc3. (A) Western blot analysis of neogenin, CDO, netrin-3, and MyoD in primary myoblasts isolated from wild-type (+/+) and Cdo−/− (−/−) mice. (B) Western blot analysis of NFATc3 in primary myoblasts of the indicated Cdo genotype treated with or without netrin-2 for 3 h. The top and bottom arrows indicate the presumptive phosphorylated and dephosphorylated forms of NFATc3, respectively.

Mentions: To gain insight into whether neogenin's ability to bind to CDO is important for netrin-neogenin signaling, primary myoblasts derived from wild-type mice and mice homozygous for a targeted mutation of Cdo were analyzed for their response to recombinant chicken netrin-2. Cdo+/+ and Cdo−/− myoblasts express similar levels of MyoD, but during differentiation Cdo−/− cells produce lower levels of myogenin and form myotubes very inefficiently (Cole et al., 2004). Like myoblast cell lines, primary myoblasts expressed netrin-3 and neogenin, regardless of their Cdo genotype (Fig. 8 A). Before treatment with netrin-2, Cdo+/+ and Cdo−/− myoblasts were similar in that each expressed somewhat higher levels of the more slowly migrating form of NFATc3 than the more quickly migrating, presumably activated, form (Fig. 8 B). After 3 h of exposure to netrin-2, the Cdo+/+ cells showed a pronounced shift to the more quickly migrating form, consistent with activation of NFAT signaling; in contrast, the Cdo−/− myoblasts showed no response and the ratio of the two forms of NFATc3 resembled that seen in untreated cells (Fig. 8 B). Therefore, loss of CDO resulted in loss of responsiveness to netrin-2 despite the presence of normal levels of its receptor, suggesting that neogenin's interaction with CDO is important for signaling by this pathway.


Netrins and neogenin promote myotube formation.

Kang JS, Yi MJ, Zhang W, Feinleib JL, Cole F, Krauss RS - J. Cell Biol. (2004)

CDO is required for netrin-2 to produce the activated form of NFATc3. (A) Western blot analysis of neogenin, CDO, netrin-3, and MyoD in primary myoblasts isolated from wild-type (+/+) and Cdo−/− (−/−) mice. (B) Western blot analysis of NFATc3 in primary myoblasts of the indicated Cdo genotype treated with or without netrin-2 for 3 h. The top and bottom arrows indicate the presumptive phosphorylated and dephosphorylated forms of NFATc3, respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172498&req=5

fig8: CDO is required for netrin-2 to produce the activated form of NFATc3. (A) Western blot analysis of neogenin, CDO, netrin-3, and MyoD in primary myoblasts isolated from wild-type (+/+) and Cdo−/− (−/−) mice. (B) Western blot analysis of NFATc3 in primary myoblasts of the indicated Cdo genotype treated with or without netrin-2 for 3 h. The top and bottom arrows indicate the presumptive phosphorylated and dephosphorylated forms of NFATc3, respectively.
Mentions: To gain insight into whether neogenin's ability to bind to CDO is important for netrin-neogenin signaling, primary myoblasts derived from wild-type mice and mice homozygous for a targeted mutation of Cdo were analyzed for their response to recombinant chicken netrin-2. Cdo+/+ and Cdo−/− myoblasts express similar levels of MyoD, but during differentiation Cdo−/− cells produce lower levels of myogenin and form myotubes very inefficiently (Cole et al., 2004). Like myoblast cell lines, primary myoblasts expressed netrin-3 and neogenin, regardless of their Cdo genotype (Fig. 8 A). Before treatment with netrin-2, Cdo+/+ and Cdo−/− myoblasts were similar in that each expressed somewhat higher levels of the more slowly migrating form of NFATc3 than the more quickly migrating, presumably activated, form (Fig. 8 B). After 3 h of exposure to netrin-2, the Cdo+/+ cells showed a pronounced shift to the more quickly migrating form, consistent with activation of NFAT signaling; in contrast, the Cdo−/− myoblasts showed no response and the ratio of the two forms of NFATc3 resembled that seen in untreated cells (Fig. 8 B). Therefore, loss of CDO resulted in loss of responsiveness to netrin-2 despite the presence of normal levels of its receptor, suggesting that neogenin's interaction with CDO is important for signaling by this pathway.

Bottom Line: These proteins stimulate myotube formation and enhance myogenic bHLH- and NFAT-dependent transcription.Furthermore, neogenin binds to CDO in a cis fashion, and myoblasts lacking CDO are defective in responding to recombinant netrin.It is proposed that netrin-3 and neogenin may promote myogenic differentiation by an autocrine mechanism as components of a higher order complex of several promyogenic cell surface proteins.

View Article: PubMed Central - PubMed

Affiliation: Brookdale Department of Molecular, Cell and Developmental Biology, Mount Sinai School of Medicine, New York, NY 10029, USA.

ABSTRACT
Differentiation of skeletal myoblasts into multinucleated myotubes is a multistep process orchestrated by several families of transcription factors, including myogenic bHLH and NFAT proteins. The activities of these factors and formation of myotubes are regulated by signal transduction pathways, but few extracellular factors that might initiate such signals have been identified. One exception is a cell surface complex containing promyogenic Ig superfamily members (CDO and BOC) and cadherins. Netrins and their receptors are established regulators of axon guidance, but little is known of their function outside the nervous system. We report here that myoblasts express the secreted factor netrin-3 and its receptor, neogenin. These proteins stimulate myotube formation and enhance myogenic bHLH- and NFAT-dependent transcription. Furthermore, neogenin binds to CDO in a cis fashion, and myoblasts lacking CDO are defective in responding to recombinant netrin. It is proposed that netrin-3 and neogenin may promote myogenic differentiation by an autocrine mechanism as components of a higher order complex of several promyogenic cell surface proteins.

Show MeSH