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MyoR is expressed in nonmyogenic cells and can inhibit their differentiation
Liming Yu1, Jerome Mikloucich, Niquiche Sangster
1Center for Functional Genomics, The University at Albany, East Campus, 1 University Place, A-202, Rensselaer, NY 12144, USA.
Abstract:
The development of skeletal muscle in mammals is promoted by the muscle-specific basic helix-loop-helix transcription factors of the MyoD family. Evidence also suggests that there are basic helix-loop-helix proteins that specifically inhibit skeletal myogenesis, including Mtwist, Mist1, and the most recently described, MyoR. It has been suggested that MyoR expression is limited to the precursors of the skeletal muscle lineage and acts as a transcriptional repressor of the muscle differentiation program. However, our results demonstrate that MyoR is expressed in several different, nonmuscle adult tissues. Furthermore, MyoR is expressed in the embryonic ectoderm of blastocyst stage mouse embryos, well before skeletal muscle specification and even before delineation of the mesodermal germ layer. Using embryonic ectoderm analogous stem cells, we demonstrate that in these nonmuscle cells, as in skeletal muscle precursor cells, expression of MyoR is inversely correlated with the extent of cellular differentiation as induced by retinoic acid. Our preliminary results indicate that overexpression of exogenous MyoR inhibits retinoic-acid-induced differentiation in EC cells and is lethal to early mouse embryos. Our results suggest a much broader role for MyoR in the repression and/or determination of embryonic cell differentiation.
Insights
MyoR, a protein previously thought to regulate muscle development, is found in various non-muscle tissues and early embryos. Its expression inhibits cellular differentiation, suggesting a broader role in embryonic development.
Area of Science:
- Developmental Biology
- Molecular Biology
- Genetics
Background:
- Basic helix-loop-helix transcription factors, like the MyoD family, are crucial for skeletal muscle development.
- Proteins such as Mtwist, Mist1, and MyoR are known to inhibit skeletal myogenesis.
- MyoR was hypothesized to be exclusively expressed in skeletal muscle precursors, acting as a repressor of muscle differentiation.
Purpose of the Study:
- To investigate the expression pattern and function of MyoR beyond its proposed role in skeletal muscle.
- To determine if MyoR plays a role in early embryonic development and non-muscle cell differentiation.
Main Methods:
- Analysis of MyoR expression in adult non-muscle tissues and early mouse embryos (blastocyst stage).
- Utilizing embryonic ectoderm-analogous stem cells to study MyoR's effect on differentiation induced by retinoic acid.
- Investigating the impact of exogenous MyoR overexpression on embryonic stem cells and early mouse embryos.
Main Results:
- MyoR expression was detected in multiple adult non-muscle tissues and in the embryonic ectoderm of blastocyst-stage mouse embryos.
- In both skeletal muscle precursor cells and embryonic ectoderm-analogous stem cells, MyoR expression inversely correlated with retinoic acid-induced differentiation.
- Overexpression of MyoR inhibited retinoic acid-induced differentiation in embryonic carcinoma (EC) cells and proved lethal to early mouse embryos.
Conclusions:
- MyoR is not limited to skeletal muscle precursors and exhibits a wider expression profile.
- MyoR functions as a repressor of cellular differentiation in various cell types and developmental stages.
- The findings suggest a significant role for MyoR in the repression and/or determination of embryonic cell differentiation, extending beyond myogenesis.