A MISSENSE MUTATION IN THE GENE ENCODING THE ALPHA(1) SUBUNIT OF THE INHIBITORY GLYCINE RECEPTOR IN THE SPASMODIC MOUSE

Hereditary hyperekplexia, an autosomal dominant neurologic disorder characterized by an exaggerated startle reflex and neonatal hypertonia, can be caused by mutations in the gene encoding the alpha(1) subunit of the inhibitory glycine receptor (GLRA1). Spasmodic (spd), a recessive neurologic mouse mutant, resembles hyperekplexia phenotypically, and the two disease loci map to homologous chromosomal regions. Here we describe a Glra1 missense mutation in spd that results in reduced agonist sensitivity in glycine receptors expressed in vitro. We conclude that spd is a murine homologue of hyperekplexia and that mutations in GLRA1/Glra1 can produce syndromes with different inheritance patterns.