Sodium Channel Dysfunction inEpilepsy and Migraine
Sodium Channel Dysfunction inEpilepsy and Migraine
Edited by professor Yasser Metwally
www.yassermetwally.com
www.yassermetwally.com
PhysiologyGeneration and propagation of action potentials
PharmacologyTargets for local anesthetics, anticonvulsants
GeneticsInherited disorders of muscle, heart, brain, nerve
PhysiologyGeneration and propagation of action potentials
PharmacologyTargets for local anesthetics, anticonvulsants
GeneticsInherited disorders of muscle, heart, brain, nerve
Voltage-Gated Sodium ChannelsVoltage-Gated Sodium Channels
Muscle Sodium Channelopathies (SCN4A)Hyperkalemia periodic paralysisParamyotonia congenitaPotassium-aggravated myotoniaHypokalemic periodic paralysis type 2Painful congenital myotoniaMyasthenic syndrome Malignant hyperthermia susceptibility Cardiac Sodium Channelopathies (SCN5A)Congenital long QT syndrome (Romano-Ward)Idiopathic ventricular fibrillation (Brugada syndrome)Isolated cardiac conduction system diseaseAtrial standstillCongenital sick sinus syndromeSudden infant death syndromeDilated cardiomyopathy, conduction disorder, supraventricular arrhythmiaBrain Sodium Channelopathies (SCN1A, SCN2A, SCN1B)Generalized epilepsy with febrile seizures plusSevere myoclonic epilepsy of infancy (Dravet syndrome)Intractable childhood epilepsy with frequent generalized tonic-clonic seizuresBenign familial neonatal-infantile seizuresFamilial hemiplegic migrainePeripheral Nerve Sodium Channelopathies (SCN9A)Familial primary erythermalgiaCongenital indifference to pain
Muscle Sodium Channelopathies (SCN4A)Hyperkalemia periodic paralysisParamyotonia congenitaPotassium-aggravated myotoniaHypokalemic periodic paralysis type 2Painful congenital myotoniaMyasthenic syndrome Malignant hyperthermia susceptibility Cardiac Sodium Channelopathies (SCN5A)Congenital long QT syndrome (Romano-Ward)Idiopathic ventricular fibrillation (Brugada syndrome)Isolated cardiac conduction system diseaseAtrial standstillCongenital sick sinus syndromeSudden infant death syndromeDilated cardiomyopathy, conduction disorder, supraventricular arrhythmiaBrain Sodium Channelopathies (SCN1A, SCN2A, SCN1B)Generalized epilepsy with febrile seizures plusSevere myoclonic epilepsy of infancy (Dravet syndrome)Intractable childhood epilepsy with frequent generalized tonic-clonic seizuresBenign familial neonatal-infantile seizuresFamilial hemiplegic migrainePeripheral Nerve Sodium Channelopathies (SCN9A)Familial primary erythermalgiaCongenital indifference to pain
Generalized epilepsy with febrile seizures plusSCN1B, SCN1A, SCN2A
Severe myoclonic epilepsy of infancySCN1A (NaV1.1)
Intractable childhood epilepsy with generalized tonic-clonic seizuresSCN1A (NaV1.1)
Benign familial neonatal-infantile seizuresSCN2A (NaV1.2)
Familial hemiplegic migraineSCN1A (NaV1.1)
Familial erythromelalgiaSCN9A (NaV1.7)
Congenital indifference to painSCN9A (NaV1.7)
Generalized epilepsy with febrile seizures plusSCN1B, SCN1A, SCN2A
Severe myoclonic epilepsy of infancySCN1A (NaV1.1)
Intractable childhood epilepsy with generalized tonic-clonic seizuresSCN1A (NaV1.1)
Benign familial neonatal-infantile seizuresSCN2A (NaV1.2)
Familial hemiplegic migraineSCN1A (NaV1.1)
Familial erythromelalgiaSCN9A (NaV1.7)
Congenital indifference to painSCN9A (NaV1.7)
Disorders of Neuronal Sodium ChannelsDisorders of Neuronal Sodium Channels
Generalized Epilepsy with Febrile Seizures Plus(GEFS+)
Generalized Epilepsy with Febrile Seizures Plus(GEFS+)
Phenotype
Familial epilepsy syndrome characterized by childhood onset of typical febrile seizures that often persist beyond age 6 years accompanied by afebrile generalized seizures exhibiting variablephenotypes (generalized tonic-clonic, absence, myoclonic, atonic, and myoclonic-astatic).
Phenotype
Familial epilepsy syndrome characterized by childhood onset of typical febrile seizures that often persist beyond age 6 years accompanied by afebrile generalized seizures exhibiting variablephenotypes (generalized tonic-clonic, absence, myoclonic, atonic, and myoclonic-astatic). Genetics
GEFS+ Type I 19q13.1Voltage-gated Na channel ß1 subunit, SCN1B
GEFS+ Type II 2q22-24Voltage-gated Na channel α subunit, SCN1A, SCN2A
GEFS+ Type III 5q31.1-33.1GABA receptor subunit γ2, GABRG2
Genetics
GEFS+ Type I 19q13.1Voltage-gated Na channel ß1 subunit, SCN1B
GEFS+ Type II 2q22-24Voltage-gated Na channel α subunit, SCN1A, SCN2A
GEFS+ Type III 5q31.1-33.1GABA receptor subunit γ2, GABRG2
19
SCN1B
2
SCN1ASCN2A
D188V T875MV1353L
R1657C
R1648HI1656M
K1270T
++++
++++
++++
W1204R
V1428AA1685V
N
C
SCN1A Mutations in GEFS+SCN1A Mutations in GEFS+
All GEFS+ mutations are missense
Heterologous Expression of SCN1AHeterologous Expression of SCN1A
tsA201 cells
pCMV-SCN1A
EGFP
hβ2
pGFP-IRES-hβ2
CD8
hβ1
pCD8-IRES-hβ1
+ CD8-antibody beads
2 days+ fluorescence
Principles of Na Channel GatingPrinciples of Na Channel Gating
resting
OutOut
InIn
Na+Na+
active
Na+Na+
fast-inactivated
Na+Na+
I Na1 μA
-10
-120 mV 1 msV
resting
OutOut
InIn
Na+Na+
active
Na+Na+
fast-inactivated
Na+Na+
Principles of Na Channel GatingPrinciples of Na Channel Gating
% persistent current vs. transient current
0.2 % (n = 4)0.9 % (n = 8, p < 0.01)1.5 % (n = 4, p < 0.001)4.2 % (n = 4, p < 0.0005)
Properties of SCN1A GEFS+ MutantsProperties of SCN1A GEFS+ MutantsR1648H, T875M, W1204RR1648H, T875M, W1204R
GEFS+ mutants exhibit increased persistent INa
Christoph Lossin, Dao Wang
Voltage (mV)
-120 -80 -40 0 40
Voltage ramp -120 to +
40 mV (20 mV/sec)
WT-SCN1A + hβ1 + hβ2
R1648H + hβ1 + hβ21 Sec
50 p
A
Responses to Voltage Ramp
R1648H exhibits inappropriate activation
Properties of SCN1A GEFS+ MutantsProperties of SCN1A GEFS+ Mutants
WT-SCN1A single channel analysisWT-SCN1A single channel analysis
B
Amplitude, pA-3 -2 -1 0
Eve
nts
0
1000
2000
3000
4000
5000
6000A
2 pA5 ms
0 mV
• WT-SCN1A channels inactivate rapidly and completelyCarlos Vanoye
Properties of SCN1A GEFS+ MutantsProperties of SCN1A GEFS+ Mutants
R1648H single channel analysisR1648H single channel analysis
A B
C D2 pA
5 ms2 pA
5 ms
0 mV -10 mV
• Late re-opening of R1648H channels explains persistent current• Bursting behavior is rare
Properties of SCN1A GEFS+ MutantsProperties of SCN1A GEFS+ Mutants
R1648H single channel analysisR1648H single channel analysis
• Late re-opening of R1648H channels explains persistent current• Bursting behavior is rare
Severe Myoclonic Epilepsy of Infancy(SMEI, Dravet syndrome)
Severe Myoclonic Epilepsy of Infancy(SMEI, Dravet syndrome)
Phenotype
Rare, often sporadic convulsive syndrome characterized by febrile seizures during the first year of life, followed by intractable generalized epilepsy, impaired psychomotor development and ataxia. Classic anti-convulsant agents (dilantin, carbamazapine) may worsen seizures. “Borderline” SMEI (SMEB) associated with less severe seizures and less developmental impairments, absence of myoclonic seizures. Sometimes diagnosed in adulthood.
Genetics
Transmission is not evident in most cases; de novo SCN1A mutations.
SMEI 2q22-24 Voltage-gated Na channel α subunit, SCN1A
Phenotype
Rare, often sporadic convulsive syndrome characterized by febrile seizures during the first year of life, followed by intractable generalized epilepsy, impaired psychomotor development and ataxia. Classic anti-convulsant agents (dilantin, carbamazapine) may worsen seizures. “Borderline” SMEI (SMEB) associated with less severe seizures and less developmental impairments, absence of myoclonic seizures. Sometimes diagnosed in adulthood.
Genetics
Transmission is not evident in most cases; de novo SCN1A mutations.
SMEI 2q22-24 Voltage-gated Na channel α subunit, SCN1A
++++
++++
++++
L986F
F891C
R921CL1255P
V1380M
W1424R
Q1440R
R1648C
G1664R
T1899I
N
C
frameshift or nonsensemissense
SCN1A Mutations in SMEISCN1A Mutations in SMEI
F1661S
G1749E
M924IV934A
del F1289
Most SMEI mutations are nonsense or frameshift
Effect of SCN1A TruncationEffect of SCN1A Truncation
X
p.A1067T
c.3608delAPremature stop codon
1 2 3 4
Western Blot probed with anti-SCN1A antibody
Human cerebellum lysates normalized for protein content
1: SMEI patient (5yo female)2: Age-matched control (5yo female)3: 24yo male control4: 28yo male control
Erin McArdle
Severity Spectrum of Epilepsies Associated with Na Channel Mutations
Severity Spectrum of Epilepsies Associated with Na Channel Mutations
GEFS+GEFS+ SMEISMEI
LessLess MoreMoreClinical SeverityClinical Severity
Gain-of-FunctionGain-of-Function Loss-of-FunctionLoss-of-Function
Provisional genotype-phenotype correlationProvisional genotype-phenotype correlation
V1353LR1657C
I1656M
++++
++++
++++
A1685VN
C
SCN1A Mutations in GEFS+SCN1A Mutations in GEFS+
V1353L and A1685V are nonfunctional
Functional heterogeneity of GEFS+ mutations
Christoph Lossin, Tommy Rhodes
Properties of SCN1A GEFS+ MutantsProperties of SCN1A GEFS+ MutantsI1656M, R1657CI1656M, R1657C
Functional heterogeneity of GEFS+ mutations
I1656MR1657C
WT-SCN1A
Variable current density Shift in activation curve
I1656M and R1657C do NOT exhibit increased persistent INa
++++
++++
++++
L986F
R1648C
G1674RN
C
SCN1A Mutations in SMEISCN1A Mutations in SMEI
F1661S
G1749E
8 – non-functional
Characterization of 13 SMEI alleles
5 - dysfunctional
G177E
I227S R393HH939Q
C959R
delF1289
T1909I
Y426N
Properties of SCN1A SMEI MutantsProperties of SCN1A SMEI MutantsG1749E, R1648C, F1661SG1749E, R1648C, F1661S
2 ms
0.2 nA
F1661SG1749E
2 ms
0.2 nA
0.5 nA
2 ms
WT-SCN1A
2 ms
0.5 nA
R1648C
Tommy Rhodes, Iori Ohmori
Properties of SCN1A SMEI MutantsProperties of SCN1A SMEI MutantsG1749E, R1648C, F1661SG1749E, R1648C, F1661S
2 ms
WT-SCN1AG1749ER1648CF1661S
Variable impairment of inactivation
TTX-sensitive late current at 200 msec:WT 0.4 ± 0.1%G1749E 0.5 ± 0.1%R1648C 3.6 ± 0.3%F1661S 3.8 ± 0.3%
50 ms
0 50 100 150 200-10
-8
-6
-4
-2
0
Nor
mal
ized
Cur
rent
(%)
Pulse Duration (ms)
WT-SCN1AG1749E
F1661SR1648C
Properties of SCN1A SMEI MutantsProperties of SCN1A SMEI MutantsG1749E, R1648C, F1661SG1749E, R1648C, F1661S
R1648C and F1661S exhibit persistent INa
Familial Hemiplegic MigraineFamilial Hemiplegic Migraine
Phenotype
Familial hemiplegic migraine is an inherited subtype of migraine with aura. Attacks are characterized by the presence of hemiparesis or hemiplegia, either isolated or associated with other aura symptoms such as hemianopic blurring of vision, unilateral paresthesias or numbness, and dysphasia. These symptoms usually last 30 to 60 minutes and are followed by a severe pulsatile headache lasting a few hours.
Genetics
Autosomal dominant
FHM1 19p13 Calcium channel α subunit, CACNA1AFHM2 1q21-q23 Na-K ATPase α2 subunit, ATP1A2FHM3 2q22-24 Voltage-gated Na channel α subunit, SCN1A
Phenotype
Familial hemiplegic migraine is an inherited subtype of migraine with aura. Attacks are characterized by the presence of hemiparesis or hemiplegia, either isolated or associated with other aura symptoms such as hemianopic blurring of vision, unilateral paresthesias or numbness, and dysphasia. These symptoms usually last 30 to 60 minutes and are followed by a severe pulsatile headache lasting a few hours.
Genetics
Autosomal dominant
FHM1 19p13 Calcium channel α subunit, CACNA1AFHM2 1q21-q23 Na-K ATPase α2 subunit, ATP1A2FHM3 2q22-24 Voltage-gated Na channel α subunit, SCN1A
SCN1A – a novel locus for familial hemiplegic migraineSCN1A – a novel locus for familial hemiplegic migraine
Dichgans, et al., Lancet 2005
Recovery at –100 mV
Voltage-dependence ofrecovery from inactivation
Expression in SCN5A
Properties of SCN1A Mutant in FHMProperties of SCN1A Mutant in FHM
Functional properties of Q1489K
Abnormal voltage-dependence of activation-4 mV shift in conductance vs voltage
Abnormal fast inactivation*increased persistent currentimpaired recovery from inactivation
Enhanced slow inactivation*Enhanced use-dependence
* Novel features
Kris Kahlig, Tommy Rhodes
1 10 100 10000.2
0.4
0.6
0.8
1.0
WT Q1489K
Nor
mal
ized
Cur
rent
Recovery period [ms]
Impaired recovery from inactivation
– 120 mV
-10 mV
∆t
WT Q1489Kτ1 (ms) 2.0 ± 0.1 1.5 ± 0.1 (P< 0.02)τ2 (ms) 54 ± 9.6 76 ± 5.0 (P < 0.05)A2 (%) 20 ± 1.0 32 ± 1.0 (P < 0.001)
50 ms
WT
Q1489K
WT 0.4%Q1489K 1.48 %
Increased persistent sodium current
Properties of SCN1A Mutant in FHMProperties of SCN1A Mutant in FHM
Kris Kahlig, Tommy Rhodes
Properties of SCN1A Mutant in FHMProperties of SCN1A Mutant in FHM
Abnormal use-dependence
0 20 40 60 80 100 120 140
0.25
0.5
0.75
1
Nor
mal
ized
cur
rent
Frequency (Pulses/Second)
WT Q1489K
Properties of SCN1A Mutant in FHMProperties of SCN1A Mutant in FHM
0 20 40 60 80 100 120 140
0.25
0.5
0.75
1
R1648H R1648C WT Q1489KN
orm
aliz
ed c
urre
nt
Frequency (Pulses/Second)
Epilepsy
Migraine
Abnormal use-dependence
Cortical Spreading Depression (CSD) of LeãoCortical Spreading Depression (CSD) of Leão
Cortical spreading depression, a transient depolarization wave that moves across the cortex, explains migraine aura.
Cortical spreading depression, a transient depolarization wave that moves across the cortex, explains migraine aura.
Leão, J Neurophysiol 1944
Role of CSD in Migraine PathogenesisRole of CSD in Migraine Pathogenesis
Summary and ConclusionsSummary and Conclusions
• Mutations in brain voltage-gated Na channels are associatedwith a diverse group of human epilepsy syndromes and rarecases of familial migraine.
• Functional defects range from loss- to gain-of-function
• Relationship between clinical syndrome and biophysicalphenotypes is complex
• Other genetic, developmental and environmental factorsmay influence the clinical expression channel mutations
• Computational modeling offers opportunities to define themechanistic basis for Na channel dysfunction and may helpwith the design of targeted therapies.
• Mutations in brain voltage-gated Na channels are associatedwith a diverse group of human epilepsy syndromes and rarecases of familial migraine.
• Functional defects range from loss- to gain-of-function
• Relationship between clinical syndrome and biophysicalphenotypes is complex
• Other genetic, developmental and environmental factorsmay influence the clinical expression channel mutations
• Computational modeling offers opportunities to define themechanistic basis for Na channel dysfunction and may helpwith the design of targeted therapies.
Role of CSD in Migraine PathogenesisRole of CSD in Migraine PathogenesisVoltage-Gated Sodium ChannelsVoltage-Gated Sodium ChannelsMuscle Sodium Channelopathies (SCN4A)Muscle Sodium Channelopathies (SCN4A)Disorders of Neuronal Sodium ChannelsDisorders of Neuronal Sodium ChannelsGeneralized epilepsy with febrile seizures plusSCN1B, SCN1A, SCN2AGeneralized epilepsy with febrile seizures plusSevere myoclonic epilepsy of infancySevere myoclonic epilepsy of infancyIntractable childhood epilepsy with generalized tonic-clonic seizures1.1)Intractable childhood epilepsy with generalized tonic-clonic seizuresBenign familial neonatal-infantile seizuresVVSCN1A (Na1.2)Familial hemiplegic migraineVSCN2A (Na1.1)Familial erythromelalgiaVSCN1A (Na1.7)Congenital indifference to pain1.7)V1BBenign familial neonatal-infantile seizures1.2)SCN2A (NaBenign familial neonatal-infantile seizures1.2)SCN2A (NaFamilial hemiplegic migraineFamilial hemiplegic migraine1.1)SCN1A (NaFamilial erythromelalgiaFamilial erythromelalgia1.7)SCN9A (NaCongenital indifference to painCongenital indifference to pain1.7)SCN9A (Na
Generalized Epilepsy with Febrile Seizures PlusGeneralized Epilepsy with Febrile Seizures PlusSevere Myoclonic Epilepsy of InfancySevere Myoclonic Epilepsy of InfancyFamilial Hemiplegic MigraineFamilial Hemiplegic MigraineRole of CSD in Migraine PathogenesisRole of CSD in Migraine PathogenesisSummary and ConclusionsSummary and Conclusions=============My web site