A GLRA1 null mutation in recessive hyperekplexia challenges the functional role of glycine receptors. |
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Authors: | W Brune R G Weber B Saul M von Knebel Doeberitz C Grond-Ginsbach K Kellerman H M Meinck and C M Becker |
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Institution: | Zentrum für Molekulare Biologie, Universität Heidelberg, Germany. |
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Abstract: | Dominant missense mutations in the human glycine receptor (GlyR) alpha 1 subunit gene (GLRA1) give rise to hereditary hyperekplexia. These mutations impair agonist affinities and change conductance states of expressed mutant channels, resulting in a partial loss of function. In a recessive case of hyperekplexia, we found a deletion of exons 1-6 of the GLRA1 gene. Born to consanguineous parents, the affected child is homozygous for this GLRA1(null) allele consistent with a complete loss of gene function. The child displayed exaggerated startle responses and pronounced head-retraction jerks reflecting a disinhibition of vestigial brain-stem reflexes. In contrast, proprio- and exteroceptive inhibition of muscle activity previously correlated to glycinergic mechanisms were not affected. This case demonstrates that, in contrast to the lethal effect of a null allele in the recessive mouse mutant oscillator (Glra1 spd-ot), the loss of the GlyR alpha 1 subunit is effectively compensated in man. |
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