Metabolic Regulation of Epithelial to Mesenchymal Transition: Implications for Endocrine Cancer

York University Librarie

p38-γ–dependent gene silencing restricts entry into the myogenic differentiation program

The regenerative capacity of muscle is regulated by p38-γ, which phosphorylates MyoD and leads to formation of a complex that represses myogenin transcription

Pax7 Induces Myogenic Commitment in CD45⁺:Sca1⁺ Cells

<div><p>(A) Western blot analysis with anti-Pax7 antibody confirmed high levels of ectopic Pax7 in C3H10T1/2 cells infected with retrovirus-Pax7 (HAN-Pax7) but not with control virus expressing a puromycin-resistance marker (HAN-puro).</p> <p>(B and C) HAN-Pax7 did not induce expression of myogenin in C3H10T1/2 cells.</p> <p>(D and E) By contrast, MyoD virus (HAN-MyoD) efficiently converted C3H10T1/2 cells to myogenin-expressing myocytes (green) .</p> <p>(F–I) HAN-Pax7 (F and G) but not HAN-puro (H and I) activated expression of MyoD (red) in CD45⁺:Sca1⁺ cells from uninjured muscle.</p> <p>(J–M) HAN-Pax7 (J) but not HAN-puro (K) also induced Myf5nLacZ expression in CD45⁺:Sca1⁺ cells. Furthermore, HAN-Pax7-infected CD45⁺:Sca1⁺ cultures differentiated into MyHC-expressing myocytes (green) under differentiation conditions (L), whereas HAN-puro-infected cells did not undergo myogenic differentiation (M). DAPI staining (blue) was used to visualize all nuclei.</p></div

Adenovirus-Pax7 Significantly Improves Regeneration In Vivo

<div><p>(A and B) Infection of ctx-damaged <i>Pax7</i><b>^−/−</b> muscles with Ad-Pax7 resulted in markedly improved muscle integrity and a significantly increased number of Desmin immunoreactive (green) regenerated fibers (B) relative to muscles treated with Ad-LacZ (A).</p> <p>(C and D) Hematoxylin and Eosin staining similarly showed an increased number of centrally nucleated fibers in Ad-Pax7-treated <i>Pax7</i><b>^−/−</b> muscles.</p> <p>(E) In three separate experimental trials, the number of regenerated fibers was markedly increased in Ad-Pax7-treated muscles relative to Ad-LacZ; however, the response was biologically variable between groups. On average, Ad-Pax7 infection resulted in a 4.1 ± 0.72–fold increase in regenerated <i>Pax7</i><b>^−/−</b> myofibers (F).</p></div

Pax7 Promotes Myogenesis in CD45⁻:Sca1⁻ Cells from <i>Pax7</i><b>^−/−</b> Muscle

<div><p>(A–C) Ectopic expression of Pax7 (HAN-Pax7) induced Myf5 expression (green) and myogenic commitment in CD45⁻:Sca1⁻ cells from <i>Pax7</i><b>^−/−</b> muscle.</p> <p>(D–F) By contrast, Myf5-expressing cells were completely absent from HAN-puro-infected cultures after selection.</p> <p>(G–L) CD45⁻:Sca1⁻ cells from <i>Pax7</i><b>^−/−</b> muscle expressed Myf5 (red) (H) and MyHC (red) (K) only in cells that also coexpressed high levels of Pax7 protein (G and J). Arrowheads indicate cells coexpressing Pax7 and Myf5/MyHC. Arrow in (G) and (I) depicts a Pax7⁺, Myf5⁻ cell.</p></div

CDSC-Pax7 Cells Become Myogenic Progenitors

<p>Myf5 (A–C) and MyoD (D–F) protein (green) are expressed in proliferating CDSC-Pax7 cells. Exposure of CD45⁺:Sca1⁺ cultures to low mitogen medium induced the formation of multinucleated myotubes and expression of myogenic differentiation markers including MyHC (red) (G–I) and myogenin (red) (J–L). Sustained expression of Pax7 (red) (M–O) in these cultures did not interfere with their differentiation. DAPI staining (blue) was used to visualize all nuclei.</p

CDSC-Pax7 Cells Efficiently Contribute to the Repair of Dystrophic Muscle

<div><p>(A) Wild-type muscle expressed dystrophin at the plasmalemma of all myofibers.</p> <p>(B) Dystrophin protein was not detected in muscle sections from <i>dystrophin</i>-deficient <i>mdx:nude</i> mice <i>(mdx:nu).</i></p> <p>(C–F) CDSC-Pax7 cells differentiated in vivo after transplantation, readily forming large numbers of dystrophin-expressing myofibers (green) in <i>mdx:nude</i> muscle (C and D). Serial cross sections showing the viral expression of Pax7 protein in central nuclei of regenerated fibers (red staining in [E]) confirmed the donor origin of dystrophin-positive myofibers (red staining in [F]).</p></div

CDSC-Pax7 Cells Express High Levels of Myf5 and Sca1

<div><p>(A) Western blot analysis of CDSC-Pax7 cells in proliferation conditions (day 0) and during differentiation (days 1–4) revealed high levels of Myf5 expression and low levels of MyoD expression. By contrast, satellite-cell-derived myoblasts (Wt-Mb) displayed the opposite profile of Myf5 and MyoD expression. Myogenin (Myg) was upregulated during the differentiation of CDSC-Pax7 and satellite-cell-derived myoblasts (Wt-diff). Note the sustained expression of Pax7 during the differentiation of CDSC-Pax7 cells. C3H10T1/2 (10T) lysate was used as a negative control.</p> <p>(B) RT-PCR analysis indicated that CDSC-Pax7 cells (two different lines) upregulated the endogenous <i>Pax7</i> mRNA. Satellite-cell-derived myoblasts (Wt-Mb) and Jurkat cells were used as positive and negative controls, respectively.</p> <p>(C) Flow cytometry indicated that CDSC-Pax7 cells lost expression of CD45 but retained high levels of Sca1. About 24% of satellite-cell-derived myoblasts (wt-myoblasts) expressed low levels of Sca1. (Black graph depicts staining with IgG-PE control antibody; red graph shows target staining using Sca1-PE or CD45-PE.)</p></div