F-function could lead to a hyperpolarization of the membrane potential, and so reduce cellular excitability and conduction. These putative mechanisms of action may be the basis of the observed phenotypic overlap found in patients with SCN5A loss-of-function variants and TRPM4 variants. In addition to direct effects of TRPM4 mutations cardiac excitability, one has to consider that these mutants may also have complex effects leading to BrS related to the fact that TRPM4 is expressed in a variety of tissues [27]. Mutations may influence neuro-hormonal regulation or cardiac development [28]. Altogether, this study suggests a role of TRPM4 in BrS accounting for 2.7 to 6 of cases. In contrast to the first 4 TRPM4 mutations reported in patients with conduction blocks [15,16], the electrophysiological consequences of the mutations resulting in BrS is more diverse at least 2 mutations resulting in decreased current density, 2 mutations with no electrophysiological anomalies in 25331948 this experimental setting, and 2 previously reported mutations with increased current. The complexity of the induced disturbances in MedChemExpress JNJ-7706621 channel electrophysiology and trafficking is increased by the genetic heterogeneity of BrS. In particular, further studies are warranted to improve our understanding of the interaction between channels that are permeable to sodium and potassium.Supporting InformationFigure S1 Activation time. Activation time of the current was determined in the whole-cell configuration using a pulse protocol from Vm = 0 to +80 mV. Currents were fitted to a double exponential to estimate time for half activation. A: Current trace for WT under a pulse protocol as showed under the trace. B: Mean time for half activation for WT and mutants. No significant differences were seen between mutants and WT. (TIF) Figure S2 Number of channels per patch detected in buy KB-R7943 inside-out configuration. Mean number of TRPM4 channels detected in each inside-out patch at Vm = +40 mV (pipette and bath: 145 mM NaCl, 1023 M Ca2+). No detectable current was observed for K914X. Number of experiments on top of bars. (TIF) Figure S3 Original western blot pictures that were including more mutants than presented in figure 6. Panels are from top to bottom: total expression and anti-TRPM4 antibody, total expression and anti-actin antibody; surface expression and anti-TRPM4 antibody; surface expression and anti-actin antibody. Lanes are from left-hand side to right-hand side: empty plasmid, size marker, wild type TRPM4, and the following TRPM4 mutants: L138P, R164W, A432T, G737R, P779R, G844D, T873I, K914X, L941M, L1075P and E7K. (TIF) Figure S4 Original pictures of western blots showing total and surface expression revealed with an anti-HA antibody. These are the original Western blot pictures that included the same lanes as in figure S3. The method used is slightly different than in western blot of figure 6 and S3 in particular an anti-HA antibody was used instead of an antiTRPM4 antibody. Note that a shorter band is clearly visible on the L914X mutant line suggesting a truncated TRPM4 mutant present in the total expression but also in the surface expression. (TIF)AcknowledgmentsThe authors are greatly indebted to patients and their families. They also thank clinicians and nurses for patients’ enrollment.Author ContributionsConceived and designed the experiments: HA JJS RG PB. Performed the experiments: HL 26001275 SC CS NS LS JM GM. Analyzed the data: HL SC CS NS LS VP JM GM ML HA JJS RG PB. Contributed.F-function could lead to a hyperpolarization of the membrane potential, and so reduce cellular excitability and conduction. These putative mechanisms of action may be the basis of the observed phenotypic overlap found in patients with SCN5A loss-of-function variants and TRPM4 variants. In addition to direct effects of TRPM4 mutations cardiac excitability, one has to consider that these mutants may also have complex effects leading to BrS related to the fact that TRPM4 is expressed in a variety of tissues [27]. Mutations may influence neuro-hormonal regulation or cardiac development [28]. Altogether, this study suggests a role of TRPM4 in BrS accounting for 2.7 to 6 of cases. In contrast to the first 4 TRPM4 mutations reported in patients with conduction blocks [15,16], the electrophysiological consequences of the mutations resulting in BrS is more diverse at least 2 mutations resulting in decreased current density, 2 mutations with no electrophysiological anomalies in 25331948 this experimental setting, and 2 previously reported mutations with increased current. The complexity of the induced disturbances in channel electrophysiology and trafficking is increased by the genetic heterogeneity of BrS. In particular, further studies are warranted to improve our understanding of the interaction between channels that are permeable to sodium and potassium.Supporting InformationFigure S1 Activation time. Activation time of the current was determined in the whole-cell configuration using a pulse protocol from Vm = 0 to +80 mV. Currents were fitted to a double exponential to estimate time for half activation. A: Current trace for WT under a pulse protocol as showed under the trace. B: Mean time for half activation for WT and mutants. No significant differences were seen between mutants and WT. (TIF) Figure S2 Number of channels per patch detected in inside-out configuration. Mean number of TRPM4 channels detected in each inside-out patch at Vm = +40 mV (pipette and bath: 145 mM NaCl, 1023 M Ca2+). No detectable current was observed for K914X. Number of experiments on top of bars. (TIF) Figure S3 Original western blot pictures that were including more mutants than presented in figure 6. Panels are from top to bottom: total expression and anti-TRPM4 antibody, total expression and anti-actin antibody; surface expression and anti-TRPM4 antibody; surface expression and anti-actin antibody. Lanes are from left-hand side to right-hand side: empty plasmid, size marker, wild type TRPM4, and the following TRPM4 mutants: L138P, R164W, A432T, G737R, P779R, G844D, T873I, K914X, L941M, L1075P and E7K. (TIF) Figure S4 Original pictures of western blots showing total and surface expression revealed with an anti-HA antibody. These are the original Western blot pictures that included the same lanes as in figure S3. The method used is slightly different than in western blot of figure 6 and S3 in particular an anti-HA antibody was used instead of an antiTRPM4 antibody. Note that a shorter band is clearly visible on the L914X mutant line suggesting a truncated TRPM4 mutant present in the total expression but also in the surface expression. (TIF)AcknowledgmentsThe authors are greatly indebted to patients and their families. They also thank clinicians and nurses for patients’ enrollment.Author ContributionsConceived and designed the experiments: HA JJS RG PB. Performed the experiments: HL 26001275 SC CS NS LS JM GM. Analyzed the data: HL SC CS NS LS VP JM GM ML HA JJS RG PB. Contributed.
