BACKGROUND: Duchenne Muscular Dystrophy (DMD) is a severe, progressive, 
neuromuscular disorder of childhood. While a number of serum factors have been 
identified as potential biomarkers of DMD, none, as yet, are proteins within the 
dystrophin-associated glycoprotein (DAG) complex.
OBJECTIVE: We have developed an immobilized serum ELISA assay to measure the 
expression of a constitutively cleaved and secreted component of the DAG 
complex, the N-terminal domain of α dystroglycan (αDG-N), and assayed relative 
expression in serum from muscular dystrophy patients and normal controls.
METHODS: ELISAs of immobilized patient or mouse serum and Western blots were 
used to assess αDG-N expression.
RESULTS: Immobilization of diluted serum on ELISA plates was important for this 
assay, as methods to measure serum αDG-N in solution were less robust. αDG-N 
ELISA signals were significantly reduced in DMD serum (27±3% decrease, n = 9, 
p < 0.001) relative to serum from otherwise normal controls (n = 38), and 
calculated serum αDG-N concentrations were reduced in DMD relative to normal 
(p < 0.01) and Becker Muscular Dystrophy (n = 11, p < 0.05) patient serum. By 
contrast, ELISA signals from patients with Inclusion Body Myositis were not 
different than normal (4±3% decrease, n = 8, p = 0.99). αDG-N serum signals were 
also significantly reduced in utrophin-deficient mdx mice as compared to mdx and 
wild type mice.
CONCLUSIONS: Our results are the first demonstration of a component of the DAG 
complex as a potential serum biomarker in DMD. Such a serum measure could be 
further developed as a tool to help reflect overall muscle DAG complex 
expression or stability.