GBE1 and glycogen storage disease due to glycogen branching enzyme deficiency: For example, the GBE1 variant responsible for the autosomal recessive trait Glycogen Branching Enzyme deficiency (GBED) has a much higher than expected frequency (~ 13%) in Western pleasure horses51, a subtype of the American Quarter Horse breed, than would be expected based on disease frequency in the Quarter Horse breed as a whole8.