Increased expression of TRPC5 in cortical lesions of the focal cortical dysplasia.

Focal cortical dysplasias (FCDs) are frequently associated with the medical refractory epilepsy in both children and adults. Transient receptor potential canonical channel 5 (TRPC5), a receptor-operated cation channel, has been well recognized as a regulator in the central nervous system. Here, we examined the expression and cellular distribution of TRPC5 in the specimens from patients with FCDIa (n = 14), FCDIIa (n = 12), and FCDIIb (n = 12) compared with the age-matched control cortex (CTX). TRPC5 mRNA and protein levels were significantly higher in FCDs compared with CTX. Immunohistochemical data showed that TRPC5 was strongly expressed in the misshapen cells, particularly in neuronal microcolumns, dysmorphic neurons, and balloon cells. Moreover, the double-label immunofluorescence analyses demonstrated that TRPC5 localized on NeuN-positive neurons. In addition, its co-localization with glutamate and gamma-aminobutyric acid (GABA) indicated that TRPC5 was distributed on both glutamatergic and GABAergic neurons. Taken together, these results suggested that increased expression of TRPC5 in FCDs and the cell-specific distribution patterns of TRPC5 in the misshapen neurons in FCDs could potentially contribute to the epileptogenesis of FCDs.