Downstream utrophin enhancer is required for expression of utrophin in skeletal muscle

 

Jun Tanihata

Faculty of Human Sciences, Waseda University

 

Duchenne muscular dystrophy is caused by the absence of the muscle cytoskeletal protein dystrophin (DYS). Utrophin (UTR) is an autosomal homologue of DYS, and overexpression of UTR is expected to compensate for the DYS deficit. Recent study showed that the UTR gene containing the UTR core promoter did not drive transgene expression in skeletal muscles. To clarify the regulatory mechanism of UTR expression, we generated a nuclear localization signal-tagged LacZ transgenic (Tg) mouse, in which the LacZ gene was driven by the downstream UTR enhancer (DUE) and the UTR promoter. The transgene mRNA expression levels were examined by RT-PCR and quantitative RT-PCR. Several tissues were stained with H&E and X-gal. The transgene expression patterns were consistent with endogenous UTR in several tissues including skeletal muscles. Transgene expression was up-regulated more in regenerating muscle than in non-regenerating muscle. We also established primary cultures of myogenic cells from this Tg mice and found that UTR up-regulation during muscle differentiation depends on the DUE motif. In conclusion, DUE is indispensable for UTR expression in skeletal muscle and primary myogenic cells from this Tg mice provide a high through-put screening system for drugs for up-regulate UTR expression.

 

Key words: Duchenne muscular dystrophy, utrophin, enhancer