Kv3.1 channelopathy: a novel loss-of-function variant and the mechanistic basis of its clinical phenotypes

Figure 1. The MRI features of the novel R317S variant. (A-D) The axial FLAIR showed multiple signal abnormalities in bilateral frontal, temporal, parietal occipital lobes. Hypointense lesions were seen on T1-weighted imaging (E) and on DWI (F).

Figure 2. Functional characterization of R317S variant. (A) Representative whole-cell current traces recorded from Xenopus laevis oocytes injected with the same amount of cRNA encoding Kv3.1 wild-type (WT) or mutant, R317S, or their 1:1 mixture mimicking the heterozygous expression. Currents were recorded during 0.5 s voltage steps ranging from −60 to +60 mV. (B) Current amplitudes assessed at the end of the voltage step to +60 mV and normalized to the mean current amplitude of WT recorded on the same experimental day. WT (n=136), R317S (n=45), ****, P<0.0001, using Mann-Whitney test. (C) Current amplitudes of WT + H2O (n=111) and WT + R317S (n=26) analyzed at the end of the voltage step to +60 mV and normalized to the mean current amplitude of WT + H2O recorded on the same day. ****, P<0.0001, using unpaired t-test. (D) Conductance-voltage relationships for the WT transcripts and R317S variant expressed alone or together with the WT. V0.5 values in mV: WT 22.6±1.9 (n=36), R317S 16.1±2.6 (n=17) and R317S + WT 21.7±2.9 (n=17) were not significantly different (one-way ANOVA with Dunnett’s multiple comparisons test).

Figure 3. In silico analysis and structural analysis of Kv3.1 potassium channel involved p.R317S mutation. (A) Top view of ribbon representation of the Kv3.1 potassium channel model and the voltage sensor domains were highlighted in dash-line circle colored in blue. (B) Side view of ribbon representation of the Kv3.1 potassium channel model and lipid bilayer were highlighted in dash-line colored in grey. (C) Rotational view of ribbon representation of the selective filter region of Kv3.1 potassium channel model. (D) The amino acid sequence alignment of selective filter regions showed the high degree conservation of these key Arginine (R0–R6) residues. (E) The schematic representation of Kv3.1 potassium channel model by cartoon diagram.

Figure 4. Structural analysis of Kv3.1 potassium channel involved known variants for MEAK, DEE, DE and myoclonus phenotypes. (A-C) The close view of different variants at positions of p.Arg317Ser, p.Arg320His and p.Arg421Val showed minimal disturbance for the adjacent configuration. (D-F) The close view of different variants at positions of p.Arg317His, p.Cys208Tyr and p.Thr399Met showed large steric hinderance, which likely disturb the protein structure or stability.