A 1.3 kb promoter fragment confers spatial and temporal expression of utrophin A mRNA in mouse skeletal muscle fibers Mark A. Stocksley a,1 , Joe V. Chakkalakal a,1 , Amanda Bradford a , Pedro Miura a , Yves De Repentigny b , Rashmi Kothary a,b , Bernard J. Jasmin a,b, * a Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ont., Canada K1H 8M5 b Ottawa Health Research Institute, Ottawa Hospital, Ottawa, Ont., Canada, K1H 8L6 Received 12 January 2005; received in revised form 2 March 2005; accepted 4 March 2005 Abstract Upregulation of utrophin in muscle is currently being examined as a potential therapy for Duchenne muscular dystrophy patients. In this context, we generated transgenic mice harboring a 1.3 kb human utrophin A promoter fragment driving expression of the lacZ gene. Characterization of reporter expression during postnatal muscle development revealed that the levels and localization of b-galactosidase parallel expression of utrophin A transcripts. Moreover, we noted that the utrophin A promoter is more active in slow soleus muscles. Additionally, expression of the reporter gene was regulated during muscle regeneration in a manner similar to utrophin A transcripts. Together, these results show that the utrophin A promoter-lacZ construct mirrors expression of utrophin A mRNAs indicating that this utrophin A promoter fragment confers temporal and spatial patterns of expression in skeletal muscle. This transgenic mouse will be valuable as an in vivo model for developing and testing molecules aimed at increasing utrophin A expression. q 2005 Elsevier B.V. All rights reserved. Keywords: Duchenne muscular dystrophy; Utrophin; Transgenic promoter reporter mouse; Neuromuscular junction; Muscle regeneration; Postnatal development 1. Introduction Duchenne muscular dystrophy (DMD) is the most common inherited disorder of skeletal muscle and results from mutations/deletions in the dystrophin gene, which prevent production of full-length dystrophin molecules (for review see [1–3]). Although the genetic defect causing DMD was identified nearly 20 years ago, there is still no cure available to stop the relentless progression of this devastating neuromuscular disorder. Of the various therapeutic strategies that are being developed, upregulation of utrophin, the autosomal homologue of dystrophin, has received consider- able attention over the last few years (for review see [4,5]). This can be partially attributed to the fact that utrophin can functionally compensate for the absence of dystrophin in mouse model systems of DMD [6–10] and, that as a component of the neuromuscular junction, utrophin likely plays an important role in the stabilization and maturation of the postsynaptic membrane domain [11–15]. Because of its potential as a therapeutic strategy for DMD and its role at the neuromuscular junction, several studies have focused on the identification of regulatory events that control expression of utrophin under a variety of conditions. In this context, we now know that two distinct full-length utrophin mRNAs differing in their 5 0 ends are transcribed from two different promoters [16]. These mRNAs code for proteins termed utrophin A and B that differ in their N-termini. Utrophin A is the isoform preferentially expressed in skeletal muscle fibers [17,18], whereas utrophin B appears restricted to vascular endothelial cells [17]. To date, most of the studies examining transcriptional events have focused on the utrophin A promoter. This promoter is TATA-less and lies within a CpG island [19,20]. Neuromuscular Disorders 15 (2005) 437–449 www.elsevier.com/locate/nmd 0960-8966/$ - see front matter q 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nmd.2005.03.008 * Corresponding author. Tel.: C613 562 5800x8383; fax: C613 562 5636. E-mail address: jasmin@uottawa.ca (B.J. Jasmin). 1 These authors are to be considered as co-first authors.