Functional substitution by TAT-utrophin in dystrophin-deficient mice.
BACKGROUND
The loss of dystrophin compromises muscle cell membrane stability and causes Duchenne muscular dystrophy and/or various forms of cardiomyopathy. Increased expression of the dystrophin homolog utrophin by gene delivery or pharmacologic up-regulation has been demonstrated to restore membrane integrity and improve the phenotype in the dystrophin-deficient mdx mouse. However, the lack of a viable therapy in humans predicates the need to explore alternative methods to combat dystrophin deficiency. We investigated whether systemic administration of recombinant full-length utrophin (Utr) or DeltaR4-21 "micro" utrophin (muUtr) protein modified with the cell-penetrating TAT protein transduction domain could attenuate the phenotype of mdx mice.


RESULTS
Recombinant TAT-Utr and TAT-muUtr proteins were expressed using the baculovirus system and purified using FLAG-affinity chromatography. Age-matched mdx mice received six twice-weekly intraperitoneal injections of either recombinant protein or PBS. Three days after the final injection, mice were analyzed for several phenotypic parameters of dystrophin deficiency. Injected TAT-muUtr transduced all tissues examined, integrated with members of the dystrophin complex, reduced serum levels of creatine kinase (11,290+/-920 U versus 5,950+/-1,120 U; PBS versus TAT), the prevalence of muscle degeneration/regeneration (54%+/-5% versus 37%+/-4% of centrally nucleated fibers; PBS versus TAT), the susceptibility to eccentric contraction-induced force drop (72%+/-5% versus 40%+/-8% drop; PBS versus TAT), and increased specific force production (9.7+/-1.1 N/cm(2) versus 12.8+/-0.9 N/cm(2); PBS versus TAT).


CONCLUSIONS
These results are, to our knowledge, the first to establish the efficacy and feasibility of TAT-utrophin-based constructs as a novel direct protein-replacement therapy for the treatment of skeletal and cardiac muscle diseases caused by loss of dystrophin.
Sonnemann
Kevin J
KJ
Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America.
Heun-Johnson
Hanke
H
Turner
Amy J
AJ
Baltgalvis
Kristen A
KA
Lowe
Dawn A
DA
Ervasti
James M
JM
D000818:Animals; D003402:Creatine Kinase / Q000097:blood; D016189:Dystrophin / Q000172:deficiency* / Q000235:genetics; D015696:Gene Products, tat / Q000235:genetics; D051379:Mice; D018101:Mice, Inbred mdx; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009137:Muscular Dystrophy, Animal / Q000188:drug therapy* / Q000473:pathology; D020388:Muscular Dystrophy, Duchenne / Q000188:drug therapy* / Q000473:pathology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D049411:Utrophin / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*
D016189:Dystrophin; D015696:Gene Products, tat; D011993:Recombinant Fusion Proteins; D049411:Utrophin; D003402:Creatine Kinase