The evolution of humans included introduction of an inactivating deletion in the CMAH gene, which eliminated biosynthesis of N-glycolylneuraminic acid from all human cells. Here we show that this human-specific sialylation change contributes to the marked discrepancy in phenotype between the mdx mouse model for Duchenne muscular dystrophy (DMD) and the human disease. Despite lacking dystrophin protein in almost all muscle cells, mdx mice show slower development, relative to overall lifespan, or reduced severity of a number of clinically relevant disease phenotypes compared to DMD patients. This is especially true for loss of ambulation, cardiac and respiratory muscle weakness, and loss of lifespan, all major phenotypes contributing to DMD morbidity and mortality. All these phenotypes occur at an earlier age or to a greater degree in mdx mice bearing a human-like mutation in the mouse Cmah gene. Altered phenotypes correlate with changes in two mechanisms; reduced strength and expression of the dystrophin-associated glycoprotein complex and increased activation of complement. Activation of complement may be driven by the increased expression of anti-Neu5Gc antibodies in Cmah−/−mdx animals and ultimately by uptake of N-glycolylneuraminic acid, a foreign glycan in humans and Cmah-deficient mice, from dietary sources. Cmah-deficient mdx mice represent a new small animal model for DMD that better approximates the human glycome and its contributions to muscular dystrophy.

Mendell JR, Janssen PM. Overexpression of Galgt2 in skeletal muscle prevents injury resulting from eccentric contractions in both mdx and wild-type mice.

A number of recent studies have demonstrated therapeutic effects of transgenes on the development of muscle pathology in the mdx mouse model for Duchenne muscular dystrophy, but none have been shown also to be effective in mouse models for laminin ␣2-deficient congenital muscular dystrophy (MDC1A). Here, we show that overexpression of the cytotoxic T cell (CT) GalNAc transferase (Galgt2) is effective in inhibiting the development of muscle pathology in the dy W mouse model of MDC1A, much as we had previously shown in mdx animals. Embryonic overexpression of Galgt2 in skeletal muscles using transgenic mice or postnatal overexpression using adenoassociated virus both reduced the extent of muscle pathology in dy W /dy W skeletal muscle. As with mdx mice, embryonic overexpression of the Galgt2 transgene in dy W /dy W myofibers inhibited muscle growth, whereas postnatal overexpression did not. Both embryonic and postnatal overexpression of Galgt2 in dy W /dy W muscle increased the expression of agrin, a protein that, in recombinant form, has been shown to ameliorate disease, whereas laminin ␣1, another disease modifier, was not expressed. Galgt2 overexpression also stimulated the glycosylation of a glycolipid with the CT carbohydrate, and glycolipids accounted for most of the CT-reactive material in postnatal overexpression experiments. These experiments demonstrate that Galgt2 overexpression is effective in altering disease progression in skeletal muscles of dy W mice and should be considered as a therapeutic target in

Overexpression of GALGT2 in skeletal muscle can stimulate the glycosylation of α dystroglycan and the upregulation of normally synaptic dystroglycan-binding proteins, some of which are dystrophin and laminin α2 surrogates known to be therapeutic for several forms of muscular dystrophy. This article describes the vascular delivery of GALGT2 gene therapy in a large animal model, the rhesus macaque. Recombinant adeno-associated virus, rhesus serotype 74 (rAAVrh74), was used to deliver GALGT2 via the femoral artery to the gastrocnemius muscle using an isolated focal limb perfusion method. GALGT2 expression averaged 44 ± 4% of myofibers after treatment in macaques with low preexisting anti-rAAVrh74 serum antibodies, and expression was reduced to 9 ± 4% of myofibers in macaques with high preexisting rAAVrh74 immunity (P < 0.001; n = 12 per group). This was the case regardless of the addition of immunosuppressants, including prednisolone, tacrolimus, and mycophenolate mofetil. GALGT2-treated macaque muscles showed increased glycosylation of α dystroglycan and increased expression of dystrophin and laminin α2 surrogate proteins, including utrophin, plectin1, agrin, and laminin α5. These experiments demonstrate successful transduction of rhesus macaque muscle with rAAVrh74.MCK.GALGT2 after vascular delivery and induction of molecular changes thought to be therapeutic in several forms of muscular dystrophy.

Overexpression of the cytotoxic T cell (CT) GalNAc transferase (Galgt2) in the skeletal muscles of transgenic mdx mice inhibits the development of muscular dystrophy. The profound effect of Galgt2 on muscular dystrophy in transgenic mice, where overexpression is begins from embryonic stages, is complicated by its additional effects on muscle growth and neuromuscular structure. Here, we use Adeno-associated virus (AAV) to show that overexpression of Galgt2 in skeletal myofibers in the early postnatal period is equally effective in inhibiting muscular dystrophy, but that it does so without altering muscle growth or neuromuscular structure. Unlike embryonic overexpression, postnatal overexpression of Galgt2 did not reproducibly increase the expression of utrophin, synaptic laminins, or dystrophin-associated glycoproteins along infected myofibers. Moreover, Galgt2 overexpression inhibited muscular dystrophy to the same extent in utrophin-deficient mdx muscles as it did in utrophin-expressing mdx muscles. Thus, Galgt2 is a molecular target for therapy in DMD that can be utilized in a manner that separates its clinical benefit from its effects on development, and its clinical benefit is distinct from that achieved by utrophin.

Recent studies have shown that a number of genes that are not mutated in various forms of muscular dystrophy may serve as surrogates to protect skeletal myofibers from injury. One such gene is Galgt2, which is also called cytotoxic T cell GalNAc transferase in mice. In this study, we show that Galgt2 overexpression reduces the development of dystrophic pathology in the skeletal muscles of mice lacking ␣ sarcoglycan (Sgca), a mouse model for limb girdle muscular dystrophy 2D. Galgt2 transgenic Sgca ؊/؊ mice showed reduced levels of myofiber damage, as evidenced by i) normal levels of serum creatine kinase activity, ii) a lack of Evans blue dye uptake into myofibers, iii) normal levels of mouse locomotor activity, and iv) near normal percentages of myofibers with centrally located nuclei. In addition, the overexpression of Galgt2 in the early postnatal period using an adeno-associated virus gene therapy vector protected Sgca ؊/؊ myofibers from damage, as observed using histopathology measurements. Galgt2 transgenic Sgca ؊/؊ mice also had increased levels of glycosylation of ␣ dystroglycan with the CT carbohydrate , but showed no up-regulation of ␤ , ␥ , ␦ , or sarcoglycan. These data , coupled with results from our previous studies , show that Galgt2 has therapeutic effects in three distinct forms of muscular dystrophy and may , therefore , have a broad spectrum of therapeutic potential for the treatment of various myopathies.

We have previously reported that mice with muscular dystrophy, including mdx mice, develop embryonal rhabdomyosarcoma (eRMS) with a low incidence after 1 year of age and that almost all such tumours contain cancer-associated p53 mutations. To further demonstrate the relevance of p53 inactivation, we created p53-deficient mdx mice. Here we demonstrate that loss of one or both p53 (Trp53) alleles accelerates eRMS incidence in the mdx background, such that almost all Trp53−/− mdx animals develop eRMS by 5 months of age. To ascertain whether increased tumour incidence was due to the regenerative microenvironment found in dystrophic skeletal muscles, we induced muscle regeneration in Trp53+/+ and Trp53−/− animals using cardiotoxin (Ctx). Wild-type (Trp53+/+) animals treated with Ctx, either once every 7 days or once every 14 days from 1 month of age onwards, developed no eRMS; however, all similarly Ctx-treated Trp53−/− animals developed eRMS by 5 months of age at the site of injection. Most of these tumours displayed markers of human eRMS, including over-expression of Igf2 and phosphorylated Akt. These data demonstrate that the presence of a regenerative microenvironment in skeletal muscle, coupled with Trp53 deficiency, is sufficient to robustly induce eRMS in young mice. These studies further suggest that consideration should be given to the potential of the muscle microenvironment to support tumourigenesis in regenerative therapies for myopathies.

Vaccination has become an important therapeutic approach to the treatment of Alzheimer's disease (AD), however, immunization with Aβ amyloid can have unwanted, potentially lethal, side effects. Here we demonstrate an alternative peptide-mimotope vaccine strategy using the SDPM1 peptide. SDPM1 is a 20 amino acid peptide bounded by cysteines that binds tetramer forms of Aβ 1-40 -and Aβ 1-42 -amyloid and blocks subsequent Aβ amyloid aggregation. Immunization of mice with SDPM1 induced peptide mimotope antibodies with the same biological activity as the SDPM1 peptide. When done prior to the onset of amyloid plaque formation, SDPM1 vaccination of APPswePSEN1(A246E) transgenic mice reduced amyloid plaque burden and Aβ 1-40 and Aβ 1-42 levels in the brain, improved cognitive performance in Morris water maze tests, and resulted in no increased T cell responses to immunogenic or Aβ peptides or brain inflammation. When done after plaque burden was already significant, SDPM1 immunization still significantly reduced amyloid plaque burden and Aβ 1-40/1-42 peptide levels in APPswePSEN1(A246E) brain without inducing encephalitogenic T cell responses or brain inflammation, but treatment at this stage did not improve cognitive function. These experiments demonstrate the efficacy of a novel vaccine approach for Alzheimer's disease where immunization with an Aβ 1-40/1-42 amyloidspecific binding and blocking peptide is used to inhibit the development of neuropathology and cognitive dysfunction.