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Expression of phospholamban mRNA during early avian muscle morphogenesis is distinct from that of alpha-actin
1Department of Medicine, University of Chicago, Illinois 60637.
Insights
Phospholamban mRNA expression in chick embryos is distinct from alpha-actins. While phospholamban appears in the heart and somites, its limb bud expression is delayed and lower compared to alpha-actins, suggesting independent regulation during myogenesis.
Area of Science:
- Developmental Biology
- Molecular Biology
- Muscle Physiology
Background:
- Phospholamban is a key regulator of cardiac muscle function.
- Its expression patterns during embryonic development are not fully understood.
- Comparison with actin isoforms can reveal insights into muscle-specific gene regulation.
Purpose of the Study:
- To investigate the spatio-temporal expression of phospholamban mRNA during early chick embryo development.
- To compare phospholamban expression with alpha-cardiac and alpha-skeletal actin during myogenesis.
- To determine if phospholamban and actin expression are coordinated in developing muscles.
Main Methods:
- In situ hybridization to detect mRNA localization in chick embryos.
- Quantitative analysis of mRNA signal intensity.
- Northern blot analysis of muscle tissue and primary cell cultures.
Main Results:
- Phospholamban transcripts were detected in the developing heart (stage 14 ventricle, stage 20 atrium) and myotomes (stage 20).
- Limb bud expression of phospholamban, alpha-cardiac actin, and alpha-skeletal actin increased by stage 28+.
- Quantitative analysis showed lower phospholamban mRNA levels in limb buds compared to myotomes, with a different ratio than alpha-actins. Phospholamban mRNA was undetectable in embryonic chick pectoralis muscle.
Conclusions:
- Phospholamban mRNA expression is initiated at distinct developmental stages in different muscle lineages.
- The expression of phospholamban mRNA appears to be regulated independently of alpha-actins in developing limb buds.
- These findings highlight differential gene regulatory mechanisms during early myogenesis.
Abstract:
We have studied the expression of phospholamban during the early development of chick embryos by in situ hybridization and have compared it to that of alpha-cardiac and alpha-skeletal actin. In adult cross-striated 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 presumptive 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 rudiments all three mRNAs were barely detectable through stage 24, but increased by stage 28+. However, quantitative analysis of signal intensity at stage 28+ indicated that less phospholamban mRNA is present in the limb bud than in the myotome since for phospholamban the ratio of the signal density in the myotome to that in the limb rudiments was about twice the value of the ratio determined for the alpha-actins. Northern blot analysis of embryonic day 11 chick fast pectoralis muscle showed that phospholamban mRNA was not detected in vivo while alpha-cardiac actin mRNA was. Moreover, no phospholamban mRNA was detected in primary cultures derived from pectoralis muscle of the same age. In concert with previous observations that phospholamban is not detectable at stage 30-32 in wing or thigh muscle, these results suggest that phospholamban mRNA is expressed independently of the alpha-actins in the limb buds during early myogenesis.