Reduced Expression of GABA A Receptor Alpha2 Subunit Is Associated With Disinhibition of DYT-THAP1 Dystonia Patient-Derived Striatal Medium Spiny Neurons

Selma Staege; Anna Kutschenko; Hauke Baumann; Hannes Glaß; Lisa Henkel; Thomas Gschwendtberger; Norman Kalmbach; Martin Klietz; Andreas Hermann; Katja Lohmann; Philip Seibler; Florian Wegner

doi:10.3389/fcell.2021.650586

Reduced Expression of GABA _A Receptor Alpha2 Subunit Is Associated With Disinhibition of DYT-THAP1 Dystonia Patient-Derived Striatal Medium Spiny Neurons

Front Cell Dev Biol. 2021 May 21:9:650586. doi: 10.3389/fcell.2021.650586. eCollection 2021.

Authors

Selma Staege^{1

2}, Anna Kutschenko¹, Hauke Baumann³, Hannes Glaß⁴, Lisa Henkel^{1

2}, Thomas Gschwendtberger^{1

2}, Norman Kalmbach¹, Martin Klietz¹, Andreas Hermann^{4

5}, Katja Lohmann³, Philip Seibler³, Florian Wegner^{1

2}

Affiliations

¹ Department of Neurology, Hannover Medical School, Hanover, Germany.
² Center for Systems Neuroscience, Hanover, Germany.
³ Institute of Neurogenetics, University of Lübeck, Lübeck, Germany.
⁴ Translational Neurodegeneration Section "Albrecht-Kossel", Department of Neurology, University of Rostock, Rostock, Germany.
⁵ German Center for Neurodegenerative Diseases Rostock/Greifswald, Rostock, Germany.

Abstract

DYT-THAP1 dystonia (formerly DYT6) is an adolescent-onset dystonia characterized by involuntary muscle contractions usually involving the upper body. It is caused by mutations in the gene THAP1 encoding for the transcription factor Thanatos-associated protein (THAP) domain containing apoptosis-associated protein 1 and inherited in an autosomal-dominant manner with reduced penetrance. Alterations in the development of striatal neuronal projections and synaptic function are known from transgenic mice models. To investigate pathogenetic mechanisms, human induced pluripotent stem cell (iPSC)-derived medium spiny neurons (MSNs) from two patients and one family member with reduced penetrance carrying a mutation in the gene THAP1 (c.474delA and c.38G > A) were functionally characterized in comparison to healthy controls. Calcium imaging and quantitative PCR analysis revealed significantly lower Ca²⁺ amplitudes upon GABA applications and a marked downregulation of the gene encoding the GABA _A receptor alpha2 subunit in THAP1 MSNs indicating a decreased GABAergic transmission. Whole-cell patch-clamp recordings showed a significantly lower frequency of miniature postsynaptic currents (mPSCs), whereas the frequency of spontaneous action potentials (APs) was elevated in THAP1 MSNs suggesting that decreased synaptic activity might have resulted in enhanced generation of APs. Our molecular and functional data indicate that a reduced expression of GABA _A receptor alpha2 subunit could eventually lead to limited GABAergic synaptic transmission, neuronal disinhibition, and hyperexcitability of THAP1 MSNs. These data give pathophysiological insight and may contribute to the development of novel treatment strategies for DYT-THAP1 dystonia.

Keywords: DYT-THAP1; GABAA receptor; calcium dynamics; genetic dystonia; induced pluripotent stem cells; patch-clamp electrophysiology; striatal medium spiny neurons.