H no widening of QRS had a rSr’ complex. This observation suggests that TRPM4 mutation screening should be considered in BrS when a widening of QRS or a rSr’ complex is observed, a condition which not rare in BrS cases. Similar to the families 22948146 with cardiac conduction blocks, no cases of left bundle branch block were observed.cellular and cell surface expression level of TRPM4 channels, WT and TRPM4 mutants were transiently transfected in HEK293 cells. Forty-eight hours post-transfection, the expression of TRPM4 channels at the total protein level and at the cell surface was assessed by quantitative Western blots (figure 6 and figure S3). Under our migration conditions, two distinct bands representing fully and core glycosylated forms of TRPM4 were observed. All mutants showed a significantly SPDP altered expression of TRPM4. The p.Pro779Arg and p.Lys914X mutants showed a decreased of total expression whereas p.Lys914X was comparable to background level. With an anti-HA antibody, a shorter band was visible in the total and the surface expression demonstrating that p.Lys914X results in the production of a truncated protein (figure S4). By contrast, the p.Thr873Ile mutant showed 
a significant increase inTable 2. Presentation of clinical and electrocardiographic features of TRPM4 variant carriers.Patient number Age at diagnostic 57 36 53 52 57 45 31 56 45 55 50 34 37 74 35 44 76 43 70 35 fainting no type 1 SD no type 1 ??fainting no type 1 ?ECG no type 2 ajmaline + ECG no type 1 ?ECG SD type 1 ?94 58 70 54 55 73 fainting no type 
2 ajmaline + 50 fainting no type 1 ?58 ECG no type 1 ?61 220 168 150 176 168 180 193 179 172 fainting no type 1 ?53 281 fainting no type 1 ?73 180 fainting no type 2 ?flecaine + 70 170 fainting SD type 1 ?105 138 113 100 120 106 120 100 120 100 105 130 87 104 107 fainting no type 1 ?58 200 140 ECG SD type 2 ?flecaine + 69 166 79 ECG no type 1 ?72 170 100 iRBBB rSr’ RBBB iRBBB iRBBB RBBB AV block+iRBBB AV block+RBBB ?RBBB+LAHB iRBBB iRBBB RBBB rSr’ iRBBB iRBBB chest pain Father: palpitations type 2 ajmaline + 80 160 100 iRBBB ECG no type 2 ajmaline + 84 166 104 ?ECG no type 2 ?flecaine + 64 160 100 iRBBB ECG no type 2 ?flecaine + 86 138 110 iRBBB Family history QT 340 400 340 320 364 349 420 346 360 400 455 360 365 480 325 372 400 369 360Mutations SexCircumstances of discoveryPharmacology Heart Spontaneous ECG challenge rateQRS PR interval durationConduction blocksQTc 407 410 402 388 399 374 415 458 391 434 423 360 359 440 407 366 432 360 370p.R144WMp.A432TMp.G555RFp.F773IMp.P779RMp.G844DMp.G844DMp.G844DMp.Q854RMp.Q854RMp.Q854RFp.T873IMp.K914XMp.K914XMp.K914XMp.L1075PMp.I1204LMp.I1204LMp.I1204LMp.I1204LMAV block: AtrioVentricular block, iRBBB and RBBB: incomplete and complete Right Bundle Branch Block, LAHB: Left Anterior HemiBlock, QTc: corrected QT interval (Bazett formula). Mutations in bold, predisposing factors in regular letters. TRPM4 RefSeq NM_017636.3, OMIM 60. doi:10.1371/journal.pone.0054131.tTRPM4 Mutations in Brugada SyndromeTRPM4 Mutations in Brugada SyndromeFigure 3. Biophysical properties of WT and mutants TRPM4 channel in whole-cell configuration. (A): Representative current tracings recorded in the whole cell conditions (ramp protocol under the 3397-23-7 biological activity traces) (B): Mean current density for WT and mutants estimated using the maximal current recorded during the ending step of 20 ms at Vm = +100 mV (see A) and reported to cell capacitance. *p,0.05, **p,0.01, ***p,0.001, ****p,0.0001, n.s.: not significant. Numbers.H no widening of QRS had a rSr’ complex. This observation suggests that TRPM4 mutation screening should be considered in BrS when a widening of QRS or a rSr’ complex is observed, a condition which not rare in BrS cases. Similar to the families 22948146 with cardiac conduction blocks, no cases of left bundle branch block were observed.cellular and cell surface expression level of TRPM4 channels, WT and TRPM4 mutants were transiently transfected in HEK293 cells. Forty-eight hours post-transfection, the expression of TRPM4 channels at the total protein level and at the cell surface was assessed by quantitative Western blots (figure 6 and figure S3). Under our migration conditions, two distinct bands representing fully and core glycosylated forms of TRPM4 were observed. All mutants showed a significantly altered expression of TRPM4. The p.Pro779Arg and p.Lys914X mutants showed a decreased of total expression whereas p.Lys914X was comparable to background level. With an anti-HA antibody, a shorter band was visible in the total and the surface expression demonstrating that p.Lys914X results in the production of a truncated protein (figure S4). By contrast, the p.Thr873Ile mutant showed a significant increase inTable 2. Presentation of clinical and electrocardiographic features of TRPM4 variant carriers.Patient number Age at diagnostic 57 36 53 52 57 45 31 56 45 55 50 34 37 74 35 44 76 43 70 35 fainting no type 1 SD no type 1 ??fainting no type 1 ?ECG no type 2 ajmaline + ECG no type 1 ?ECG SD type 1 ?94 58 70 54 55 73 fainting no type 2 ajmaline + 50 fainting no type 1 ?58 ECG no type 1 ?61 220 168 150 176 168 180 193 179 172 fainting no type 1 ?53 281 fainting no type 1 ?73 180 fainting no type 2 ?flecaine + 70 170 fainting SD type 1 ?105 138 113 100 120 106 120 100 120 100 105 130 87 104 107 fainting no type 1 ?58 200 140 ECG SD type 2 ?flecaine + 69 166 79 ECG no type 1 ?72 170 100 iRBBB rSr’ RBBB iRBBB iRBBB RBBB AV block+iRBBB AV block+RBBB ?RBBB+LAHB iRBBB iRBBB RBBB rSr’ iRBBB iRBBB chest pain Father: palpitations type 2 ajmaline + 80 160 100 iRBBB ECG no type 2 ajmaline + 84 166 104 ?ECG no type 2 ?flecaine + 64 160 100 iRBBB ECG no type 2 ?flecaine + 86 138 110 iRBBB Family history QT 340 400 340 320 364 349 420 346 360 400 455 360 365 480 325 372 400 369 360Mutations SexCircumstances of discoveryPharmacology Heart Spontaneous ECG challenge rateQRS PR interval durationConduction blocksQTc 407 410 402 388 399 374 415 458 391 434 423 360 359 440 407 366 432 360 370p.R144WMp.A432TMp.G555RFp.F773IMp.P779RMp.G844DMp.G844DMp.G844DMp.Q854RMp.Q854RMp.Q854RFp.T873IMp.K914XMp.K914XMp.K914XMp.L1075PMp.I1204LMp.I1204LMp.I1204LMp.I1204LMAV block: AtrioVentricular block, iRBBB and RBBB: incomplete and complete Right Bundle Branch Block, LAHB: Left Anterior HemiBlock, QTc: corrected QT interval (Bazett formula). Mutations in bold, predisposing factors in regular letters. TRPM4 RefSeq NM_017636.3, OMIM 60. doi:10.1371/journal.pone.0054131.tTRPM4 Mutations in Brugada SyndromeTRPM4 Mutations in Brugada SyndromeFigure 3. Biophysical properties of WT and mutants TRPM4 channel in whole-cell configuration. (A): Representative current tracings recorded in the whole cell conditions (ramp protocol under the traces) (B): Mean current density for WT and mutants estimated using the maximal current recorded during the ending step of 20 ms at Vm = +100 mV (see A) and reported to cell capacitance. *p,0.05, **p,0.01, ***p,0.001, ****p,0.0001, n.s.: not significant. Numbers.
