Dual AAV amelioration of Lama2-null muscular dystrophy and neuropathy

The dy ^3K /dy ^3K Lama2 ^-/- mouse is a model for the severe form of LAMA2-related dystrophy and peripheral neuropathy (LAMA2-RD). In the dystrophic mice, a compensating laminin subunit, Lmα4, that lacks polymerization and α-dystroglycan-binding activity, replaces the missing Lmα2 subunit. It was previously found that an α4-laminin can be modified with two small laminin-binding linker proteins, i.e. αLNNdΔG2' and miniagrin to facilitate polymerization and α-dystroglycan binding respectively, to enable the key missing functions. Adeno-associated virus serotype 9 (AAV ₉ ) was used to deliver minigenes coding for the two proteins in dystrophic mice. AAV ₉ -αLNNdΔG2' utilized a universal CBh promoter while AAV ₉ -miniagrin utilized either the CBh promoter or muscle-specific SPc5-12 promoter. The phenotype in the dy ^3K /dy ^3K mice was evaluated following i.v. postnatal injection with either AAV ₉ -αLNNdΔG2' alone or in combination with AAV ₉ - αLNNdΔG2' + AAV _9- miniagrin. Double AAV treatment was found to substantially increase survival and ambulation, as well as increase forelimb grip-strength and improve muscle histology. Of note, the sciatic nerve amyelination characteristic of laminin α2-deficiency was prevented. While single treatment with αLNNdΔG2' was inferior to double treatment for muscle strength and survival, it corrected the radial sorting deficit equally, revealing that enablement of laminin polymerization is a sufficient requirement for myelination.

The dy ^3K /dy ^3K (Lama2 ^-/- ) mouse, a model for severe LAMA2-related dystrophy, expresses laminin-411 that is unable to polymerize or bind to α-dystroglycan (αDG). αLNNdΔG2' and miniagrin are laminin-411-binding proteins that enable polymerization and αDG binding. AAV ₉ delivery of genes coding for αLNNdΔG2' and miniagrin ameliorated the dystrophic phenotype in muscle and nerve (survival, growth, mobility, and grip-strength, muscle and nerve histopathology). Sciatic nerve amyelination was prevented by αLNNdΔG2' alone.