The human gephyrin (GPHN) gene: structure, chromosome localization and expression in non-neuronal cells

Gephyrin was first described as a peripheral membrane protein of 93 kDa anc horing the glycine receptor (GlyR) to subsynaptic microtubules and cytoskel eton. Analysis of knock-out mice demonstrated that gephyrin has additional functions in GABA(A) receptor localization at the synapse and in the biosyn thetic pathway of the molybdenum cofactor (Moco). Here we describe a human non-neuronal gephyrin cDNA and the exon/intron organization of the human ge phyrin gene. We found the coding region to consist of 27 exons and to span approximately 800 kb on the long arm of chromosome 14. This structure is al most identical to that of the mouse gephyrin gene except that sequences cor responding to three exons described in rat and mouse could not be identifie d in human. Mutations of the GlyR subunits and of gephyrin lead to severe n euromotor phenotypes in human and mouse. Hyperekplexia involves most freque ntly a mutation in the GlyR alpha1 subunit in humans. However, inactivation of the Moco biosynthesis pathway results in very similar symptomatology. T he recent characterization of a deletion of two exons of the gephyrin gene in a patient with symptoms typical of Moco deficiency confirmed that the in volvement of gephyrin in these pathologies cannot be excluded. The precise localization of the gephyrin gene allowed us to exclude it from being a can didate for the autosomal dominant spastic paraplegia, the locus of which ma ps to 14q between markers D14S259 and D14S1018. A description of its struct ure and exon boundaries should lay the groundwork for further analysis of i ts expression in humans. (C) 2001 Published by Elsevier Science B.V. All ri ghts reserved.