SLC6A5 and hereditary hyperekplexia: The genetic causes for startle disease have been defined, with the most common gene GLRA1 (encoding the GlyR α1 subunit) followed by SLC6A5 (glycine transporter 2) and GLRB (GlyR β subunit; Harvey et al., 2008; Chung et al., 2010; James et al., 2013).