The International Journal of Developmental Biology

Int. J. Dev. Biol. 50: 47 - 54 (2006)

Comparative expression analysis of Pax3 and Pax7 during mouse myogenesis

David Horst1,4, Svetlana Ustanina2, Consolato Sergi3, Gregor Mikuz3, Herbert Juergens1, Thomas Braun2 and Eugene Vorobyov4,*

1Klinik und Poliklinik für pädiatrische Hämatologie/Onkologie, Universitätsklinikum Münster, Germany, 2Max Planck Institut für Herz- und Lungenforschung, Bad Nauheim, Germany, 3Institut für Pathologie, Medizinische Universität Innsbruck, Austria and 4Institut für Humangenetik, Universitätsklinikum Münster, Germany


Pax3 and Pax7 are closely related transcription factors involved in the commitment of myogenic precursors in the developing trunk. However, it is not yet clear whether these genes are required for myogenic cell specification in the head and for post-somitic myogensis per se. In part, this uncertainty is due to the scarce information about their normal time course and pattern of expression. Here, we present a systematic immunohistochemical in situ analysis of spatiotemporal characteristics of Pax3 and Pax7 protein expression in comparison to that of MyoD and myogenin in the developing trunk and head muscles. The observed patterns of expression suggest that Pax3 is not involved in myogenesis in the head and its post-somitic expression in the trunk and limb muscles is mostly repressed after stage E13.5. In contrast, Pax7 expression is shared among all striated muscles and exhibits a uniform pattern. Pax7 is expressed only in mononucleated cells that either differentiate into myotubes or later form satellite cells. During development of head muscles, expression of Pax7 follows expression of MyoD and myogenin, implying that Pax7 is not required to induce the initial steps of the myogenic program in the head. In Pax7 homozygous mutants, in which muscle development proceeds normally, expression of Pax3 is indistinguishable from its wild-type pattern (i. e. absent), suggesting that after stage E13.5 myogenesis does not require Pax3 and Pax7. These data challenge the concept that Pax3 and Pax7 determine a persistent lineage of myogenic precursors in pre-natal and post-natal muscle development.


Pax3, Pax7, myogenesis, development

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