Trigeminal neuralgia (TN) is a rare form of chronic neuropathic pain characterized by spontaneous or elicited paroxysms of electric shock-like or stabbing pain in a region of the face. While most cases occur in a sporadic manner and are accompanied by intracranial vascular compression of the trigeminal nerve root, alteration of ion channels has emerged as a potential exacerbating factor. Recently, whole exome sequencing analysis of familial TN patients identified 19 rare variants in the gene CACNA1H encoding for Cav3.2T-type calcium channels. An initial analysis of 4 of these variants pointed to a pathogenic role. In this study, we assessed the electrophysiological properties of 13 additional TN-associated Cav3.2 variants expressed in tsA-201 cells. Our data indicate that 6 out of the 13 variants analyzed display alteration of their gating properties as evidenced by a hyperpolarizing shift of their voltage dependence of activation and/or inactivation resulting in an enhanced window current supported by Cav3.2 channels. An additional variant enhanced the recovery from inactivation. Simulation of neuronal electrical membrane potential using a computational model of reticular thalamic neuron suggests that TN-associated Cav3.2 variants could enhance neuronal excitability. Altogether, the present study adds to the notion that ion channel polymorphisms could contribute to the etiology of some cases of TN and further support a role for Cav3.2 channels.

• Klíčová slova
• CACNA1H, Calcium channel, Cav3.2 channel, Channelopathy, Ion channel, Trigeminal neuralgia,
• MeSH
• elektrofyziologické jevy MeSH
• lidé MeSH
• membránové potenciály MeSH
• neuralgie trigeminu * genetika   MeSH
• neurony MeSH
• vápníkové kanály MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• CACNA1H protein, human MeSH Prohlížeč
• vápníkové kanály MeSH

Developmental and epileptic encephalopathies (DEEs) are a group of severe epilepsies that are characterized by seizures and developmental delay. DEEs are primarily attributed to genetic causes and an increasing number of cases have been correlated with variants in ion channel genes. In this study, we report a child with an early severe DEE. Whole exome sequencing showed a de novo heterozygous variant (c.4873-4881 duplication) in the SCN8A gene and an inherited heterozygous variant (c.952G > A) in the CACNA1H gene encoding for Nav1.6 voltage-gated sodium and Cav3.2 voltage-gated calcium channels, respectively. In vitro functional analysis of human Nav1.6 and Cav3.2 channel variants revealed mild but significant alterations of their gating properties that were in general consistent with a gain- and loss-of-channel function, respectively. Although additional studies will be required to confirm the actual pathogenic involvement of SCN8A and CACNA1H, these findings add to the notion that rare ion channel variants may contribute to the etiology of DEEs.

• Klíčová slova
• CACNA1H, Calcium channel, Cav3.2 channel, Channelopathy, Encephalopathy, Epilepsy, Ion channels, Nav1.6 channel, SCN8A, Sodium channel,
• MeSH
• aktivační mutace MeSH
• bodová mutace MeSH
• duplikace genu MeSH
• epilepsie tonicko-klonická genetika   MeSH
• gating iontového kanálu genetika   fyziologie   MeSH
• genetická predispozice k nemoci MeSH
• lidé MeSH
• missense mutace MeSH
• mnohočetné abnormality genetika   MeSH
• napěťově řízený sodíkový kanál, typ 6 genetika   fyziologie   MeSH
• novorozenec MeSH
• refrakterní epilepsie genetika   MeSH
• rodokmen MeSH
• skolióza genetika   MeSH
• vápníkové kanály - typ T genetika   fyziologie   MeSH
• vývojové poruchy u dětí genetika   MeSH
• Check Tag
• lidé MeSH
• novorozenec MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• CACNA1H protein, human MeSH Prohlížeč
• napěťově řízený sodíkový kanál, typ 6 MeSH
• SCN8A protein, human MeSH Prohlížeč
• vápníkové kanály - typ T MeSH

Low-voltage-activated T-type calcium channels are important contributors to nervous system function. Post-translational modification of these channels has emerged as an important mechanism to control channel activity. Previous studies have documented the importance of asparagine (N)-linked glycosylation and identified several asparagine residues within the canonical consensus sequence N-X-S/T that is essential for the expression and function of Cav3.2 channels. Here, we explored the functional role of non-canonical N-glycosylation motifs in the conformation N-X-C based on site directed mutagenesis. Using a combination of electrophysiological recordings and surface biotinylation assays, we show that asparagines N345 and N1780 located in the motifs NVC and NPC, respectively, are essential for the expression of the human Cav3.2 channel in the plasma membrane. Therefore, these newly identified asparagine residues within non-canonical motifs add to those previously reported in canonical sites and suggest that N-glycosylation of Cav3.2 may also occur at non-canonical motifs to control expression of the channel in the plasma membrane. It is also the first study to report the functional importance of non-canonical N-glycosylation motifs in an ion channel.

• Klíčová slova
• Asparagine-linked glycosylation, Calcium channel, N-glycosylation, Non-canonical glycosylation, T-type channel, Trafficking, cav3.2 Channel,
• MeSH
• aminokyselinové motivy MeSH
• asparagin metabolismus   MeSH
• glykosylace MeSH
• lidé MeSH
• vápníkové kanály - typ T chemie   metabolismus   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• asparagin MeSH
• CACNA1H protein, human MeSH Prohlížeč
• vápníkové kanály - typ T MeSH

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the progressive loss of cortical, brain stem and spinal motor neurons that leads to muscle weakness and death. A previous study implicated CACNA1H encoding for Cav3.2 calcium channels as a susceptibility gene in ALS. In the present study, two heterozygous CACNA1H variants were identified by whole genome sequencing in a small cohort of ALS patients. These variants were functionally characterized using patch clamp electrophysiology, biochemistry assays, and molecular modeling. A previously unreported c.454GTAC > G variant produced an inframe deletion of a highly conserved isoleucine residue in Cav3.2 (p.ΔI153) and caused a complete loss-of-function of the channel, with an additional dominant-negative effect on the wild-type channel when expressed in trans. In contrast, the c.3629C > T variant caused a missense substitution of a proline with a leucine (p.P1210L) and produced a comparatively mild alteration of Cav3.2 channel activity. The newly identified ΔI153 variant is the first to be reported to cause a complete loss of Cav3.2 channel function. These findings add to the notion that loss-of-function of Cav3.2 channels associated with rare CACNA1H variants may be risk factors in the complex etiology of ALS.

• Klíčová slova
• ALS, Amyotrophic lateral sclerosis, Biophysics, CACNA1H, Calcium channel, Cav3.2 channel, Motor neuron disease, Mutation, T-type channel,
• MeSH
• amyotrofická laterální skleróza * genetika   MeSH
• dominantní geny MeSH
• genetická predispozice k nemoci * MeSH
• genetické asociační studie * MeSH
• heterozygot MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• mutace * genetika   MeSH
• sekvence aminokyselin MeSH
• sekvenování celého genomu MeSH
• strukturní homologie proteinů MeSH
• vápníkové kanály - typ T * chemie   genetika   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• CACNA1H protein, human MeSH Prohlížeč
• vápníkové kanály - typ T * MeSH