T. Toyofuku et al., EXPRESSION OF PHOSPHOLAMBAN MESSENGER-RNA DURING EARLY AVIAN MUSCLE MORPHOGENESIS IS DISTINCT FROM THAT OF ALPHA-ACTIN, Developmental dynamics, 196(2), 1993, pp. 103-113
We have studied the expression of phospholamban during the early devel
opment of chick embryos by in situ hybridization and have compared it
to that of alpha-cardiac and alpha-skeletal actin. In adult cross-stri
ated muscles there is only one phospholamban gene and it is expressed
exclusively in the heart and slow muscles. In the heart phospholamban
transcripts were first detected at stage 14 in the region of presumpti
ve ventricle and at stage 20 in the atrium. In the myotomal portion of
the somites phospholamban mRNA was first detected at stage 20, which
lagged behind the appearance of the alpha-actins. In the limb rudiment
s all three mRNAs were barely detectable through stage 24, but increas
ed by stage 28+. However, quantitative analysis of signal intensity at
stage 28+ indicated that less phospholamban mRNA is present in the li
mb bud than in the myotome since for phospholamban the ratio of the si
gnal density in the myotome to that in the limb rudiments was about tw
ice the value of the ratio determined for the alpha-actins. Northern b
lot analysis of embryonic day 11 chick fast pectoralis muscle showed t
hat phospholamban mRNA was not detected in vivo while alpha-cardiac ac
tin mRNA was. Moreover, no phospholamban mRNA was detected in primary
cultures derived from pectoralis muscle of the same age. In concert wi
th previous observations that phospholamban is not detectable at stage
30-32 in wing or thigh muscle, these results suggest that phospholamb
an mRNA is expressed independently of the alpha-actins in the limb bud
s during early myogenesis. (C) 1993 Wiley-Liss, Inc.