¹Gencell S.A.S., 72-82 Rue Léon Geoffroy, 94408 Vitry sur Seine Cedex, France

Correspondence: Vincent Thuillier, Fax: +33 1 5893 2422. E-mail: vincent.thuillier@gencell.com

^*Present address: Aventis Pharma, 13 Quai Jules Guesde, 94403 Vitry sur Seine, France.

^†Present address: Cytokinetics, 280 East Grand Avenue, South San Francisco, CA 94080, USA.

^‡Present address: Exelixis, Inc., 170 Harbor Way, P.O. Box 511, South San Francisco, CA 94083-0511, USA.

^§Present address: Genfit, Parc Eurasanté–Lille Métropole, 885 Rue Eugène Avinée, 59120 Loos, France.

Received 14 November 2003; Accepted 19 February 2004.

Abstract

We have developed a gene switch based on the human transcription factor peroxisome proliferator-activated receptor (PPAR) and its activation by rosiglitazone. However, ectopic expression of PPAR has been demonstrated to convert myogenic cells into adipocyte-like cells and, more generally, may interfere with the physiology of the target tissue. Consequently we modified the DNA-binding specificity of PPAR, resulting in a transcription factor that we named PPAR^*. We demonstrated by histological and molecular assessment of cell phenotype that the overexpression of PPAR^* did not alter the myogenic differentiation program of G8 myoblasts. We showed that PPAR^* does not transactivate promoters containing PPAR-responsive elements but transactivates promoters containing PPAR^*-responsive elements that are at least 80% identical to a 20-bp consensus. We improved the rosiglitazone-dependent gene switch by tuning PPAR^* expression with a scaffold/matrix attachment region and by expressing both PPAR^* and the reporter gene under the control of PPAR^*-responsive elements. Treatment of cultured murine muscle cells (myotubes) with rosiglitazone induced reporter gene expression from assay background up to the level attained by a CMV I/E promoter–enhancer. These results indicate the potential of the PPAR^* gene switch for use in gene therapy applications.