N-cadherin Activation Substitutes for the Cell Contact Control in Cell Cycle Arrest and Myogenic Differentiation

Abstract

N-cadherin is expressed throughout skeletal myogenesis and has been proposed to be involved in the differentiation program of myogenic precursors. Here, we further characterize the N-cadherin involvement and its mechanism of action at the onset of differentiation, through controlled N-cadherin activation by plating isolated C2 myoblasts on surfaces coated with a chimeric Ncad-Fc homophilic ligand (N-cadherin ectodomain fused to the immunoglobulin G Fc fragment). We show that N-cadherin activation substitutes for the cell density in myogenic differentiation by promoting myogenin and troponin T expression. In addition, N-cadherin adhesion participates to the associated cell cycle arrest through the nuclear accumulation of cyclin-dependent kinase inhibitors p21 and p27. Mouse primary myoblast cultures exhibited similar responses to N-cadherin as C2 cells. RNA interference knockdowns of the N-cadherinassociated cytoplasmic proteins p120 and ␤-catenin produced opposite effects on the differentiation pathway. p120 silencing resulted in a decreased myogenic differentiation, associated with a reduction in cadherin-catenin content, which may explain its action on myogenic differentiation. ␤-Catenin silencing led to a stimulatory effect on myogenin expression, without any effect on cell cycle. Our results demonstrate that N-cadherin adhesion may account for cell-cell contact-dependent cell cycle arrest and differentiation of myogenic cells, involving regulation through p120 and ␤-catenins.

Trpc1 Ion Channel Modulates Phosphatidylinositol 3-Kinase/Akt Pathway during Myoblast Differentiation and Muscle Regeneration

“…4). We also observed a significantly decreased expression of p27, a well known cdk inhibitor, which in synergy with MyoD, induces a withdrawal from the cell cycle and initiates differentiation (38,39).…”

“…In regenerating muscles, we observed that MyoD and p27 expression was lower in Trpc1 Ϫ/Ϫ than in Trpc1 ϩ/ϩ regenerating muscles. These two proteins seem to induce cell cycle arrest in response to cell-cell contact and to promote myoblast differentiation (38,39). We therefore pro- pose that the decreased expression of MyoD and p27 might be a consequence of the delayed alignment and cell-cell contacts of Trpc1 Ϫ/Ϫ myoblasts.…”

N-cadherin ligation, but not Sonic hedgehog binding, initiates Cdo-dependent p38α/β MAPK signaling in skeletal myoblasts

“…The Cdo ectodomain does not interact with itself in trans and has no obvious adhesive properties, but it binds several proteins as a putative coreceptor (9,(11)(12)(13)(14). In myoblasts, Cdo forms cis complexes with the cell-cell adhesion molecule N-cadherin (Ncad) (11), which is itself promyogenic (15)(16)(17)(18)(19)(20). Cell-cell contact stimulates myoblast differentiation, and although Ncad is not essential for myogenesis (likely due to redundancy with other cadherins) (21), direct Ncad ligation can substitute for cell-cell contact to enhance muscle-specific gene expression and myoblast differentiation (17,19).…”

“…Cell-cell contact stimulates myoblast differentiation, and although Ncad is not essential for myogenesis (likely due to redundancy with other cadherins) (21), direct Ncad ligation can substitute for cell-cell contact to enhance muscle-specific gene expression and myoblast differentiation (17,19). The ubiquitous cadherin-associated protein p120-catenin is important for Ncad's effects in myoblasts but the signaling mechanisms that drive a muscle-specific response are unknown (17,22). Cdo also binds directly to the secreted morphogen, Sonic hedgehog (Shh), perhaps as a coreceptor for Patched1, to promote Shh pathway signaling (13,14).…”

“…In myoblasts, Cdo forms cis complexes with the cell-cell adhesion molecule N-cadherin (Ncad) (11), which is itself promyogenic (15)(16)(17)(18)(19)(20). Cell-cell contact stimulates myoblast differentiation, and although Ncad is not essential for myogenesis (likely due to redundancy with other cadherins) (21), direct Ncad ligation can substitute for cell-cell contact to enhance muscle-specific gene expression and myoblast differentiation (17,19). The ubiquitous cadherin-associated protein p120-catenin is important for Ncad's effects in myoblasts but the signaling mechanisms that drive a muscle-specific response are unknown (17,22).…”