A De Novo Mutation in the Sodium-Activated Potassium Channel KCNT2 Alters Ion Selectivity and Causes Epileptic Encephalopathy
Sushmitha Gururaj,
Elizabeth Emma Palmer,
Garrett D. Sheehan,
Tejaswi Kandula,
Rebecca Macintosh,
Kevin Ying,
Paula Morris,
Jiang Tao,
Kerith-Rae Dias,
Ying Zhu,
Marcel E. Dinger,
Mark J. Cowley,
Edwin P. Kirk,
Tony Roscioli,
Rani Sachdev,
Michael E. Duffey,
Ann Bye,
Arin Bhattacharjee
Affiliations
Sushmitha Gururaj
Pharmacology and Toxicology, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA
Elizabeth Emma Palmer
Sydney Children’s Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia; Genetics of Learning Disability Service, Waratah, NSW 2298, Australia
Garrett D. Sheehan
Pharmacology and Toxicology, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA
Tejaswi Kandula
Sydney Children’s Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia
Rebecca Macintosh
Sydney Children’s Hospital, Randwick, NSW 2031, Australia
Kevin Ying
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
Paula Morris
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
Jiang Tao
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
Kerith-Rae Dias
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
Ying Zhu
Genetics of Learning Disability Service, Waratah, NSW 2298, Australia; SEALS Pathology, Randwick, NSW 2031, Australia
Marcel E. Dinger
University of New South Wales, Sydney, NSW 2031, Australia; Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
Mark J. Cowley
University of New South Wales, Sydney, NSW 2031, Australia; Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2298, Australia
Edwin P. Kirk
Sydney Children’s Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia; SEALS Pathology, Randwick, NSW 2031, Australia
Tony Roscioli
Sydney Children’s Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia; SEALS Pathology, Randwick, NSW 2031, Australia
Rani Sachdev
Sydney Children’s Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia
Michael E. Duffey
Physiology and Biophysics, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA
Ann Bye
Sydney Children’s Hospital, Randwick, NSW 2031, Australia; University of New South Wales, Sydney, NSW 2031, Australia
Arin Bhattacharjee
Pharmacology and Toxicology, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA; Program for Neuroscience, University at Buffalo - The State University of New York, Buffalo, NY 14214, USA; Corresponding author
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. : Gururaj et al. report a KCNT2 mutation in a patient with epileptic encephalopathy and employ electrophysiological analyses to establish channel properties that could underlie epileptogenesis: namely, inhibition by high [Cl−]i and loss of exclusive selectivity to K+. Furthermore, primary neurons expressing Ph240Leu display a hyperexcitable phenotype. Keywords: seizures, epileptic encephalopathy, ion channels, potassium channels, Slick, KCNT2, selectivity, Xenopus oocytes, Slack, KCNT1
