Pw. Gunning et al., alpha-Skeletal actin induces a subset of muscle genes independently of muscle differentiation and withdrawal from the cell cycle, J CELL SCI, 114(3), 2001, pp. 513-524
Muscle differentiation is characterized by the induction of genes encoding
contractile structural proteins and the repression of nonmuscle isoforms fr
om these gene families. We have examined the importance of this regulated o
rder of gene expression by expressing the two sarcomeric muscle actins char
acteristic of the differentiated state, i.e. alpha -skeletal and alpha -car
diac actin, in C2 mouse myoblasts, Precocious accumulation of transcripts a
nd proteins for a group of differentiation-specific genes was elicited by a
lpha -skeletal actin only: four muscle tropomyosins, two muscle actins, des
min and MyoD, The nonmuscle isoforms of tropomyosin and actin characteristi
c of the undifferentiated state continued to be expressed, and no myosin he
avy or light chain or troponin transcripts characteristic of muscle differe
ntiation were induced, Stable transfectants displayed a substantial reducti
on in cell surface area and in the levels of nonmuscle tropomyosins and bet
a -actin, consistent with a relationship between the composition of the act
in cytoskeleton and cell surface area. The transfectants displayed normal c
ell cycle progression. We propose that alpha -skeletal actin can activate a
regulatory pathway linking a subset of muscle genes that operates independ
ently of normal differentiation and withdrawal from the cell cycle.