3 years ago

A De Novo Mutation in the Sodium-Activated Potassium Channel KCNT2 Alters Ion Selectivity and Causes Epileptic Encephalopathy

A De Novo Mutation in the Sodium-Activated Potassium Channel KCNT2 Alters Ion Selectivity and Causes Epileptic Encephalopathy
Arin Bhattacharjee, Rani Sachdev, Edwin P. Kirk, Mark J. Cowley, Michael E. Duffey, Tony Roscioli, Tejaswi Kandula, Marcel E. Dinger, Paula Morris, Rebecca Macintosh, Kevin Ying, Kerith-Rae Dias, Ann Bye, Garrett D. Sheehan, Sushmitha Gururaj, Jiang Tao, Elizabeth Emma Palmer, Ying Zhu

Summary

Early infantile epileptic encephalopathies (EOEE) are a debilitating spectrum of disorders associated with cognitive impairments. We present a clinical report of a KCNT2 mutation in an EOEE patient. The de novo heterozygous variant Phe240Leu SLICK was identified by exome sequencing and confirmed by Sanger sequencing. Phe240Leu rSlick and hSLICK channels were electrophysiologically, heterologously characterized to reveal three significant alterations to channel function. First, [Cl]i sensitivity was reversed in Phe240Leu channels. Second, predominantly K+-selective WT channels were made to favor Na+ over K+ by Phe240Leu. Third, and consequent to altered ion selectivity, Phe240Leu channels had larger inward conductance. Further, rSlick channels induced membrane hyperexcitability when expressed in primary neurons, resembling the cellular seizure phenotype. Taken together, our results confirm that Phe240Leu is a "change-of-function" KCNT2 mutation, demonstrating unusual altered selectivity in KNa channels. These findings establish pathogenicity of the Phe240Leu KCNT2 mutation in the reported EOEE patient.

Publisher URL: http://www.cell.com/cell-reports/fulltext/S2211-1247(17)31408-0

DOI: 10.1016/j.celrep.2017.09.088

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