Distribution of the epilepsy-related Lgi1 protein in rat cortical neurons.

The Lgi1 protein is involved in the pathogenesis of autosomal dominant lateral temporal epilepsy because mutations in the leucine-rich, glioma-inactivated 1 (LGI1) gene have been found in affected subjects and families; however, the function of Lgi1 is still unclear. Definition of the fine intracellular distribution of Lgi1 in normal cortical tissue would add in understanding its role and envisage pathogenetic mechanisms. Therefore, we analyzed normal rat cortex for Lgi1 by combining biochemistry, immunohistochemistry and immunoelectron microscopy. Our results demonstrate that Lgi1 is a cytoplasmic protein distributed both in the soma and in the processes of neurons: it occurs on the rough endoplasmic reticulum, the site of synthesis, in the Golgi complex, where it undergoes glycosylation, and in close proximity to neurotubules and neurofilaments, especially in the axons, but it is scarce at synapses and the neurilemma. Lgi1 association with axonal cytoskeletal structures would imply Lgi1 is either transported along axons by motor proteins, or playing some role as a carrier in the axonal Xux, or it could be involved in the regulation of cytoskeletal organization.