Constitutive PS1 expression leads to suppression of myogenic
differentiation and augmentation of Pax7 expression. The effects of PS1 on
satellite cell function were examined by constitutively expressing PS1 using
expression vectors. (A,B) Primary satellite-cell-derived myoblasts were
transfected with either control pMSCV-IRES-GFP (Cont) or
pMSCV-PS1-IRES-GFP (PS1) vectors and, 48 hours later, immunostained
for eGFP (to identify transfected cells) and either MyHC (A) or MyoD (B)
(arrowheads indicate GFP+MyoD– cells in
PS1-vector-transfected cells). (D,E) Constitutive PS1 expression significantly
reduced the percentage of transfected cells that co-expressed either MyHC (D),
or MyoD (E). (C,F) Constitutive PS1 expression also increased the percentage
of satellite-cell-derived myoblasts expressing Pax7. (F) Although exposure of
control pMSCV-IRES-GFP-transfected cells to 1 μM DAPT reduced the
percentage of Pax7-expressing cells, DAPT inhibition of γ-secretase did
not prevent the significant increase of Pax7 in transfected cells containing
pMSCV-PS1-IRES-GFP vector. Data from at least three independent
experiments is shown ± s.d. Asterisks in D-F indicate that data are
significantly different from control values (P<0.05). Scale bars:
100 μm (A) and 30 μm (B,C).