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Pursuing a PhD: My Journey of Discovery and Future Research Directions
Krekwit Shinlapawittayatorn, MD, PhDCardiac Electrophysiology Research & Training Center (CERT)
Department of Physiology, Chiang Mai University
November 21st, 2011
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Introduction: Education
• 2004 Doctor of Medicine (M.D.)Chiang Mai UniversityChiang Mai, Thailand
• 2006-2011 Ph.D. (Physiology & Biophysics)Case Western Reserve UniversityCleveland, OH, USA
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Case Western Reserve University (CWRU) and Department of Physiology and Biophysics
• CWRU was founded in 1826.
• CWRU is a private research university located in Cleveland, OH, USA.
• The University is associated with 16 Nobel Laureates.
• The department is currently ranked #9 based on NIH funding.
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Dissertation
Modulations of Sodium Channel Long QT and Brugada Syndrome Mutations
by a Common Sodium Channel Polymorphism
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Genetic Defects of Cardiac Ion Channels: From the Bench to Bedside
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Cardiac Sodium Channelopathies: One Gene, Many Diseases
SCN5A (Gene)
Nav1.5 (Protein)
Sudden Infant Death
Syndrome
Still Birth
Brugada
Syndrome
Cardiac Conduction Defect
Sick Sinus Syndrome
Dilated Cardiomyopath
y
Atrial Fibrillation
Gain-of-function
Loss-of-function
Long QT 3 Syndrome
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Same Genetic Mutation, Different Genetic Disease Phenotype???
1 2 3
Variable Expressivity
Incomplete Penetrance
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Why do phenotypes show differences in penetrance and expressivity???
Unresolved Question:
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Pedigree of an Asymptomatic Family Carrying a Gain-of-Function Mutation of Sodium Channels
Shinlapawittayatorn et al., Heart Rhythm 2011;8(3):455-62
H558R H558R
H558R H558R+P2006A H558R H558R+P2006A
H558R+P2006A
1 2
1 2
I
II
H558R H558R
H558R H558R+P2006 H558R H558R+P2006A
H558R+P2006A
1 2
1 2
I
II
P2006AH558R
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General hypothesis
This led us to hypothesize that sodium channel H558R polymorphism may contribute to the genotype-phenotype discordance observed in
heritable arrhythmias by acting as diseases modifying gene.
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2 Peer Reviewed Articles From PhD Project
1. Shinlapawittayatorn K, Dudash L, Poelzing S, Ficker E, and Deschênes I. Cardiac Sodium Channel Fragments Spanning H558R Polymorphism Rescue Defective Trafficking of a Brugada Syndrome Mutation. Circ Cardiovasc Genet 2011;4(5):500-9. (IF = 4.043)
2. Shinlapawittayatorn K, Du X, Liu H, Ficker E, Kaufman ES, Deschênes I. A Common SCN5A Polymorphism Restores the Biophysical Defects of SCN5A Mutations. Heart Rhythm 2011;8(3):455-62. (IF = 4.246)
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4 Other Peer Reviewed Articles
1. Shinlapawittayatorn K, Deschênes I. Sodium Channel Polymorphisms and Arrhythmogenic Events: Pro-Arrhythmic or Anti-Arrhythmic? (in preparation)
2. Shinlapawittayatorn K, Sorrentino S, Forleo C, Anaclerio M, Iacoviello M, Guida P, Favale S, Ficker E, Santis DD, Nalin I, Deschênes I. Evidence for a Novel Gene (KCNQ1) Underlying Brugada Syndrome. (in preparation)
3. Abu Jawdeh BG, Khan S, Deschênes I, Hoshi M, Goel M, Lock JT, Shinlapawittayatorn K, Babcock G, Lakhe-Reddy S, DeCaro G, Yadav SP, Mohan ML, Naga Prasad SV, Schilling WP, Ficker E, and Schelling JR. Phosphoinositide Binding Differentially Regulates NHE1 Na+/H+ Exchanger-Dependent Proximal Tubule Cell Survival. J Biol Chem 2011 (in press, IF = 5.328)
4. Hsu K, Han J, Shinlapawittayatorn K, Deschênes I, Marbán E. Membrane Potential Depolarization As a Triggering Mechanism for Vpu-Mediated HIV-1 Release. Biophysical Journal 2010;99(6):1718-25. (IF = 4.218)
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1 Editorial Comments
1. Shinlapawittayatorn K, Deschênes I. Alteration of Tyrosine Kinase Signaling: Another Player in the Arrhythmogenesis of Atrial Fibrillation? Heart Rhythm 2010;7(9):1253-4. (IF = 4.246)
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10 Peer Reviewed Abstracts
1. Shinlapawittayatorn K, Du X, Liu H, Nassal DM, Liu H, Enweane P, Deschênes I. A Novel Loss-of-Function Mechanism for Brugada Syndrome Sodium Channel Mutations. Heart Rhythm 2011.
2. Shinlapawittayatorn K, Nassal DM, Liu H, Ficker E, Deschênes I. Dominant-Negative Suppression of Sodium Channel Activity By a Brugada Syndrome Mutation Observed in Cardiomyocytes. Biophys J 2011.
3. Kuri B, Nassal DM, Shinlapawittayatorn K, Ficker E, Deschênes I. Identification of KChIP2 in Guinea Pig Heart. Biophys J 2011.
4. Du X, Enweana P, Shinlapawittayatorn K, Liu H, Deschênes I. A Novel Mechanism of Action for Sodium Channel Brugada Syndrome Mutations. Heart Rhythm 2010;7(11):1716.
5. Shinlapawittayatorn K, Du X, Liu H, Ficker E, Deschênes I. Do Sodium Channel α-α. Interactions Contribute to Loss-of-Function Observed in Brugada Syndrome? Biophys J 2010.
6. Sorrentino S, Shinlapawittayatorn K, Forleo C, Anaclerio M, Iacoviello M, Nalin I, De Santis D, Zaccaria M, Ficker E, Guida P, Deschênes I, Favale S. Evidence for a Novel Gene (KCNQ1) Underlying Brugada Syndrome. Societa Italiana di Cardiologia-70○ Congresso Nazionale 2009.
7. Sorrentino S, Shinlapawittayatorn K, Forleo C, Anaclerio M, Iacoviello M, De Santis D, Nalin I, Ficker E, Favale S, Deschênes I. A Novel Gene (KCNQ1) Is Involved in Brugada Syndrome. ESC Congress 2009.
8. Shinlapawittayatorn K, Sorrentino S, Anaclerio M, Guida P, Iacoviello M, Favale S, Ficker E, Forleo C, Deschênes I. Evidence for a Novel Gene (KCNQ1) Underlying Brugada Syndrome. Heart Rhythm 2009.
9. Shinlapawittayatorn K, Du X, Liu H, Kaufman ES, Deschênes I. A Common SCN5A Polymorphism Restores the Biophysical Defects of LQT3 Mutations. Biophys J 2009.
10. Shinlapawittayatorn K, Kaufman ES, Deschênes I. SCN5A Polymorphism Decreases Arrhythmogenic Events in a Family Carrying a LQT3 Mutation. Biophys J 2008;94:3087.
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Honors and Awards
• 2011 Finalist of Student Research Achievement Award (Category: Membrane Biophysics), 55nd Annual Meeting of the Biophysical Society, Baltimore, Maryland, USA
• 2009 First Place Graduate Student Poster Presentation (Department Annual Retreat), Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, USA
• 2009 First Place of the Trainee’s Poster Presentation Competition (Research Festival), MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio, USA
• 2008 American Heart Association Pre-doctorol Fellowship Award (Percentile Rank: 0.93), American Heart Association, Great Rivers Affiliate, USA
• 2008 Finalist of Student Research Achievement Award (Category: Membrane Biophysics), 52nd Annual Meeting of the Biophysical Society, Long Beach, California, USA
• 2007 First Place of the Trainee’s Oral Presentation Competition (Genetic Basis of Cardiovascular Disease), MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio, USA
• 2007 Recknagel Graduate Student Best Academic Record, Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, USA
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Future Directions
• Patch clamp recording facility (research and training)
- Isolated cardiomyocytes
- Drug screening
- Molecular autopsy
- Personalized medicine: patient-specific iPSC
• TRF research grant for new scholar
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Acknowledgements
MetroHealth Medical Center
Case Western Reserve University
Ph.D. Thesis Guidance CommitteeThomas M. Nosek, PhDGeorge R. Dubyak, PhDStephen W. Jones, PhDKevin J. Donahue, MDKenneth R. Laurita, PhDRobert D. Harvey, PhDIsabelle Deschênes, PhD
Chiang Mai Medical School
CERT CenterNipon Chattipakorn, MD, PhD
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Thank You For Your Attention
“nor is there any better way to advance the proper practice of medicine than to give our minds to the discovery of the usual form of nature, by careful
investigation of the rarer forms of disease”
William Harvey (1657)
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Cardiac Voltage-Gated Sodium Channel (Gene: SCN5A, Protein: Nav1.5)
α (260 kD)
NH2COOH
++
++
++
++
COOH COOH
NH2NH2DI DII DIII DIV
β2 β1
β (36 kD)
S1 S2S3 S4S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6
S4 segments:Voltage sensors
S5-S6 loops: Pore of the channel
Domains III-IV linker: Inactivation gate
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Heterologous Expression of Nav1.5
HEKcells
Patch clamp
Fluorescence
HEKcells
HEKcells
1 day
Nav1.5
GFP-IRES
Vector
SCN5A-WT
SCN5A-P2006A
SCN5A-H558R-P2006A
HEK293 cells
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Using Fluorescence Resonance Energy Transfer (FRET) to Examine Sodium Channel Folding
CFP
Donor
YFP
Acceptor
Excitation
FRET
EmissionFRETc = (IDA – aIAA –
dIDD)/IDD
CNC
N
FRET
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Persistent sodium current
Model of Rescued a Gain-of-Function Mutation by the H558R Polymorphism
Ventricular myocytes action potential
0 nA
30
0
-30
-60
-90
Mem
bra
ne
po
ten
tial
(m
V)
Peak sodium current
4
0
1 2
4
3
Na+
Defective Inactivation
Na+
Stabilized Inactivation
Inward
Outward
INa
ICa
IK
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Fragment Design
COOH
NH2
++
++
++
++
282
558
N548
L567R558
R558-20aaR558-20aaG538
S577
R558
R558-40aaR558-40aa
DI DII DIII DIV
Nav1.5
N548
L567H558
H558-20aaH558-20aa