Development Genes and Evolution

, Volume 214, Issue 8, pp 380–392 | Cite as

Transcription of MyoD and myogenin in the non-contractile electrogenic cells of the weakly electric fish, Sternopygus macrurus

  • Jung A. Kim
  • Colleen B. Jonsson
  • Tiffany Calderone
  • Graciela A. Unguez
Original Article


The MyoD family of basic helix-loop-helix (bHLH) myogenic regulatory factors (MRFs) are transcriptional activators of skeletal muscle gene expression and are pivotal in inducing the full myogenic program. The expression of these factors after muscle differentiation is complete and the mechanism by which they modulate (or maintain) the muscle phenotype is less well understood. The myogenically derived electric organ (EO) of the electric fish Sternopygus macrurus is an excellent model to address this question. The electrocytes, i.e., the electrogenic cells of the EO, are not contractile but they do retain some muscle proteins. In order to examine the molecular regulatory pathways that control the muscle-to-electrocyte cell conversion, we have cloned the MyoD and myogenin cDNAs from S. macrurus. Clustal-based alignments showed that the functional domains observed in mammalian MyoD and myogenin are highly conserved in these MRF homologs. Expression analyses revealed that mature electrocytes, which retain the muscle proteins dystrophin, desmin, acetylcholine receptors (AChRs), α-actin, and α-actinin, also transcribe the MyoD and myogenin genes. RT-PCR studies confirmed that expression of these MRFs is confined to the myogenic lineage. Surprisingly, the levels of MyoD and myogenin transcripts in skeletal muscle and EO could not be used to predict the level to which a cell manifests the muscle program. We conclude that expression of multiple MRFs is not sufficient to induce non-contractile cells to fully express the skeletal muscle program. These data also suggest that the MRF transcriptional program in S. macrurus may be distinct from MRF-dependent myogenesis in other vertebrate systems.


MyoD Myogenin Electrocytes Electric fish 



This research was supported by National Institute of Health Grants S06-GM08136-27 and RR16480-01 (G.A.U.). We are grateful to Michael Peck and Xiaolin Xu for technical assistance in early studies of cloning and northern blot analysis; Dr. Dominique Mornet (Institut Bousson-Bertrand, Montpellier, France) for dystrophin antibodies; and Steve Konieczny and Harold Zakon for critical reading of the manuscript.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Jung A. Kim
    • 1
  • Colleen B. Jonsson
    • 2
  • Tiffany Calderone
    • 1
    • 3
  • Graciela A. Unguez
    • 1
  1. 1.Department of BiologyNew Mexico State UniversityLas CrucesUSA
  2. 2.Department of Biochemistry and Molecular BiologySouthern Research InstituteBirminghamUSA
  3. 3.UT-MDAnderson Cancer CenterHoustonUSA

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