Pax3 Inhibits Myogenic Differentiation of Cultured Myoblast Cells

doi:10.1074/jbc.270.20.11719

Pax3 Inhibits Myogenic Differentiation of Cultured Myoblast Cells (*)

From the (1) Divisions of Cardiology and
(2) Genetics, Brigham and Women's Hospital and Harvard Medical School, Howard Hughes Medical Institute, Boston, Massachusetts 02115 and the
(3) Department of Experimental Oncology, Saint Jude Children's Research Hospital, Memphis, Tennessee 38101

^§To whom correspondence should be addressed:
Thorn 910, HHMI, Brigham and Women's Hospital, 20 Shattuck St., Boston, MA 02115.
Tel.: 617-732-5979; Fax: 617-738-5575.

Abstract

Pax3 is an evolutionarily conserved transcription factor expressed in the lateral dermomyotome, a region that gives rise to limb muscle progenitors. Mutations in Pax-3 account for the mouse mutant Splotch which develops without limb musculature. We demonstrate that Pax3 can inhibit myogenic differentiation of C2C12 myoblasts normally induced by exposure to low serum. Specific missense mutations that affect the DNA binding characteristics of the two distinct DNA binding domains of Pax3 abolish this effect. Furthermore, we show that Pax3 can inhibit myogenic differentiation of 10T1/2 fibroblasts transfected with MyoD, but not of 10T1/2 cells transfected with myogenin. This anti-myogenic property is shared by a PAX3-forkhead fusion protein resulting from a t(2;13) chromosomal translocation found in pediatric alveolar rhabdomyosarcomas. These results suggest that Pax3 may suppress the terminal differentiation of migrating limb myoblasts and that the PAX3-forkhead fusion may contribute to the phenotype of alveolar rhabdomyosarcoma by preventing terminal differentiation.

Footnotes

↵* This work was supported by the Howard Hughes Medical Institute, National Institutes of Health Grant CA-23099, Cancer Center Core Grant CA-21765, and the American Lebanese Syrian Associated Charities. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

bHLH

basic helix-loop-helix

HA

hemagglutinin

EMSA

electrophoretic mobility shift assays

CAT

chloramphenicol acetyltransferase

SEAP

secreted alkaline phosphatase.
↵²J. A. Epstein and R. L. Maas, unpublished results.