MATR3 and distal myopathy: Given the low expression of MATR3 in the skeletal muscle and spinal cord of normal adult mice and that MATR3 gene trap mice were not reported to display a phenotype akin to ALS or distal myopathy [14], we sought to determine whether increasing expression of WT or mutant MATR3 through transgenesis would produce ALS or myopathic phenotypes.