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. 2004 Apr;24(8):3514–3525. doi: 10.1128/MCB.24.8.3514-3525.2004

FIG. 6.

FIG. 6.

Rescue of the differentiation deficiency in TIS7−/− MSCs by forced expression of TIS7 or by laminin supplementation. (a) TIS7+/+ MSCs fused to form myotubes when exposed to differentiation medium (DM). (b) TIS7−/− MSCs displayed a significant loss of fusion potential when exposed to DM. (c) TIS7−/− MSCs infected with recombinant Celo-TIS7 virus (TIS7-CT cultures) and exposed to DM for 5 days exhibited increased numbers of differentiated myocytes, as detected with antiserum MF20 reactive with MHC, and the formation of elongated bipolar multinucleated myotubes was restored (day 3, MF20). (d) Laminin supplementation enhances the fusion potential of TIS7+/+ MSCs. (e) TIS7−/− cells supplemented with laminins exhibited increased numbers of differentiated myotubes, and the formation of multinucleated myotubes was restored. Note the malformed unpolar multinucleated myotubes in TIS7−/− cells supplemented with laminins. (f) The defect in TIS7−/− MSC cytomorphology in DM (supplemented with laminin) could be partially rescued by Celo-TIS7 virus infection. (g) The isotypic Celo-GFP virus control did not affect the fusion potential of TIS7+/+ MSCs. (h) The differentiation and fusion potential of TIS7−/− MSCs remained unaltered after infection with an isotypic Celo-GFP virus control. Bar, 20 μm. (i) Fusion indices indicated a fourfold increase in the fusion potential of TIS7-CT cells relative to uninfected TIS7−/− cells. Labels below columns correspond to the same labels in panels a to h; error bars indicate standard deviations. Fusion indices were calculated as described in the legend to Fig. 4. (j) Western blot analysis revealed the expression of TIS7 protein in TIS7+/+ MSCs and its absence in TIS7−/− MSCs or TIS7-CG cells. GFP expression was detected with anti-GFP antibody. However, pools of TIS7-CT cells expressed readily detectable TIS7 protein, as detected by the Myc tag in the Celo-TIS7 virus protein.