Novel calcineurin A (PPP3CA) variant associated with epilepsy, constitutive enzyme activation and downregulation of protein expression

Eur J Hum Genet. 2019 Jan;27(1):61-69. doi: 10.1038/s41431-018-0254-8.

Małgorzata Rydzanicz ¹, Małgorzata Wachowska ², Erik C Cook ³, Paweł Lisowski ⁴ ⁵, Bożena Kuźniewska ⁶, Krystyna Szymańska ⁷, Sebastian Diecke ⁵, Alessandro Prigione ⁵, Krzysztof Szczałuba ¹, Aleksandra Szybińska ⁸, Agnieszka Koppolu ¹ ⁹, Victor Murcia Pienkowski ¹ ⁹, Joanna Kosińska ¹, Małgorzata Wiweger ⁸, Grażyna Kostrzewa ¹, Małgorzata Brzozowska ¹⁰, Dorota Domańska-Pakieła ¹¹, Elżbieta Jurkiewicz ¹², Piotr Stawiński ¹, Agnieszka Gromadka ¹³, Piotr Zielenkiewicz ¹³, Urszula Demkow ², Magdalena Dziembowska ⁶, Jacek Kuźnicki ⁸, Trevor P Creamer ³, Rafał Płoski ¹⁴

Affiliations

1 Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland.
2 Department of Laboratory Diagnostics and Clinical Immunology of Developmental Age, Medical University of Warsaw, Warsaw, Poland.
3 Center for Structural Biology and Department of Molecular & Cellular Biochemistry, University of Kentucky, Lexington, USA.
4 Institute of Genetics and Animal Breeding of the Polish Academy of Sciences, Jastrzębiec, Poland.
5 Max-Delbrück-Center for Molecular Medicine (MDC) in the Helmholtz Association, Berlin, Germany.
6 Centre of New Technologies, University of Warsaw, Warsaw, Poland.
7 Department of Experimental and Clinical Neuropathology, Mossakowski Medical Research Center, Polish Academy of Sciences, Warsaw, Poland.
8 International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland.
9 Postgraduate School of Molecular Medicine, Medical University of Warsaw, Warsaw, Poland.
10 Department of Forensic Medicine, Medical University of Warsaw, Warsaw, Poland.
11 Department of Child Neurology and Epileptology, The Children's Memorial Health Institute, Warsaw, Poland.
12 Department of Diagnostic Imaging, The Children's Memorial Health Institute, Warsaw, Poland.
13 Department of Bioinformatics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
14 Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland. rploski@wp.pl.

PMID: 30254215 DOI: 10.1038/s41431-018-0254-8

Abstract

PPP3CA encodes calmodulin-binding catalytic subunit of Calcineurin, a ubiquitously expressed calcium/calmodulin-regulated protein Phosphatase. Recently de novo PPP3CA variants were reported as a cause of disease in 12 subjects presenting with epileptic encephalopathy and dysmorphic features. We describe a boy with similar phenotype and severe early onset epileptic encephalopathy in whom a novel de novo c.1324C>T (p.(Gln442Ter)) PPP3CA variant was found by whole exome Sequencing. Western blot experiments in patient's cells (EBV transformed lymphocytes and neuronal cells derived through reprogramming) indicate that despite normal mRNA abundance the protein expression level is strongly reduced both for the mutated and wild-type protein. By in vitro studies with recombinant protein expressed in E. coli we show that c.1324C>T (p.(Gln442Ter)) results in constitutive activation of the Enzyme. Our results confirm the role of PPP3CA defects in pathogenesis of a distinct neurodevelopmental disorder including severe epilepsy and dysmorphism and provide further functional clues regarding the pathogenic mechanism.

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