Jl. Wiedenman et al., MUSCLE-SPECIFIC AND INDUCIBLE EXPRESSION OF 293-BASE PAIR BETA-MYOSINHEAVY-CHAIN PROMOTER IN TRANSGENIC MICE, American journal of physiology. Regulatory, integrative and comparative physiology, 40(3), 1996, pp. 688-695
The DNA regulatory element(s) involved in beta-myosin heavy chain (bet
a-MHC) induction by the physiological stimulus of mechanical overload
have not been identified as yet. To delineate regulatory sequences tha
t are required for mechanical overload induction of the beta-MHC gene,
transgenic mouse lines were generated that harbor transgenes containi
ng serial deletions of the human beta-MHC promoter to nucleotides -293
(beta 293), -201 (beta 201), and -141 (beta 141) from the transcripti
on start site (+1). Mechanically overloaded adult plantaris and soleus
muscles contained 11- and 1.9-fold increases, respectively, in endoge
nous beta-MHC-specific mRNA transcripts (Northern blot) compared with
sham-operated controls. Expression assays (chloramphenicol acetyltrans
ferase specific activity) revealed that only transgene beta 293 expres
sion was muscle specific in both fetal and adult mice and was induced
in the plantaris (10- to 27-fold) and soleus (2- to 2.5-fold) muscles
by mechanical overload. Histochemical staining for myosin adenosinetri
phosphatase activity revealed a fiber-type transition of type II to ty
pe I in the overloaded plantaris and soleus muscles. These transgenic
data suggest that sequences located between nucleotides -293 and +120
may be sufficient to regulate the endogenous beta-MHC gene in response
to developmental signals and to the physiological signals generated b
y mechanical overload in fast- and slow-twitch muscles.