Role of Genetic Testing for Sudden Death Predisposing Heart Conditions in Athletes
Sudden death in a young competitive athlete occurs with a prevalence of approximately 1 per 100,000 athletes per year [2, 3]. Despite its rarity, the sudden death of an athlete is devastating to both the family and community.
KeywordsGenetic Testing Sudden Cardiac Death Brugada Syndrome Sudden Unexpected Death Catecholaminergic Polymorphic Ventricular Tachycardia
To directly determine a DNA sequence, a primer binds to the region of interest on the sample DNA and initiates polymerization of DNA which is terminated in small amounts after each nucleotide addition. Each resulting oligonucleotide is labeled with a fluorescent tag identifying the sequence of the final nucleotide. The collection of fluorescent products is separated based on size, where the smallest fragment represents the first sequenced nucleotide, and the sequence is determined by the order of the nucleotide-specific fluorescent signals. Generally, this can yield a DNA sequence up to 800 nucleotides per reaction.
DNA sequence of a gene that is present in the mature mRNA after splicing removal of introns. Generally, the exonic DNA sequence ultimately codes for the corresponding amino acid sequence of the protein. There is exonic sequence at the termini of the mature mRNA of variable lengths which do not code for protein in this manner and remain untranslated (5′ and 3′ untranslated regions).
The basic hereditary unit of life which, in humans, is composed of a DNA sequence traditionally containing “coding” exonic sequence that is ultimately transcribed into mRNA and translated into protein as well as intervening “noncoding” intronic sequences which are removed during transcription and do not code for protein.
The hereditary information of an organism encoded by nucleic acid including all chromosomes. In humans, there are two complete homologous sets of DNA – one paternal and one maternal – and are thus considered diploid genomes.
The cells within an organism that pass genetic information to progeny. In humans, this refers to sperm and egg cells specifically.
A gene’s DNA sequence that is removed during splicing of the mature mRNA and does not ultimately code for protein during translation.
Changes in the DNA sequence of an organism. In humans, mutations can generally be described as synonymous (does not ultimately alter the coding protein sequence) or nonsynonymous (does ultimately alter the original coding sequence). Nonsynonymous mutations include missense (altering a single amino acid), nonsense (changes an amino acid to a stop codon which truncates the protein), and insertion/deletion (addition or subtraction of DNA which often shifts the open reading frame of the gene resulting in an altered, “frame-shifted,” protein sequence after that point and usually an early truncation of the protein). For the hypertrophic cardiomyopathy-associated missense mutation, TNNT2-R92W, for example, the DNA mutation has changed an arginine amino acid (R) to a tryptophan (W) at position 92 of the protein troponin T which is encoded by TNNT2.
A conglomeration of recently developed DNA sequencing methodologies capable of sequencing over 20 × 109 nucleotides per reaction depending on the platform .
Sample (patient) DNA is fluorescently labeled and exposed to a microarray chip containing thousands of short sequences of DNA (oligonucleotides) corresponding to mutated sequences of the genes of interest. If a mutation is present in the patient, it will bind (hybridize) to the known oligonucleotide on the chip and deliver an identifiable fluorescent signal.
- 16.Dalal D, Molin LH, Piccini J, Tichnell C, James C, Bomma C, Prakasa K, Towbin JA, Marcus FI, Spevak PJ, Bluemke DA, Abraham T, Russell SD, Calkins H, Judge DP. 2006. Clinical features of arrhythmogenic right ventricular dysplasia/cardiomyopathy associated with mutations in plakophilin-2. Circulation. 113(13):1641–1649.PubMedCrossRefGoogle Scholar
- 17.van Tintelen JP, Entius MM, Bhuiyan ZA, Jongbloed R, Wiesfeld ACP, Wilde AAM, van der Smagt J, Boven LG, Mannens MMAM, van Langen IM, Hofstra RMW, Otterspoor LC, Doevendans PAFM, Rodriguez L-M, van Gelder IC, Hauer RNW. 2006. Plakophilin-2 mutations are the major determinant of familial arrhythmogenic right ventricular dysplasia/cardiomyopathy. Circulation. 113(13):1650–1658.PubMedCrossRefGoogle Scholar
- 18.Pilichou K, Nava A, Basso C, Beffagna G, Bauce B, Lorenzon A, Frigo G, Vettori A, Valente M, Towbin J, Thiene G, Danieli GA, Rampazzo A. 2006. Mutations in desmoglein-2 gene are associated with arrhythmogenic right ventricular cardiomyopathy. Circulation. 113(9):1171–1179.PubMedCrossRefGoogle Scholar
- 23.Ackerman M, Tester D, Jones G, Will M, Burrow C, Curran M. 2003. Ethnic differences in cardiac potassium channel variants: implications for genetic susceptibility to sudden cardiac death and genetic testing for congenital long QT syndrome. Mayo Clin Proc. 78(12):1479–1487.PubMedCrossRefGoogle Scholar
- 24.Ackerman MJ, Splawski I, Makielski JC, Tester DJ, Will ML, Timothy KW, Keating MT, Jones G, Chadha M, Burrow CR, Stephens JC, Xu C, Judson R, Curran ME. 2004. Spectrum and prevalence of cardiac sodium channel variants among black, white, Asian, and Hispanic individuals: Implications for arrhythmogenic susceptibility and Brugada/long QT syndrome genetic testing. Heart Rhythm. 1(5):600–607.PubMedCrossRefGoogle Scholar
- 26.Wilde AA, Jongbloed RJ, Doevendans PA, Duren DR, Hauer RN, van Langen IM, van Tintelen JP, Smeets HJ, Meyer H, Geelen JL. 1999. Auditory stimuli as a trigger for arrhythmic events differentiate HERG- related (LQTS2) patients from KVLQT1-related patients (LQTS1). J Am Coll Cardiol. 33(2):327–332.PubMedCrossRefGoogle Scholar
- 27.Moss AJ, Robinson JL, Gessman L, Gillespie R, Zareba W, Schwartz PJ, Vincent GM, Benhorin J, Heilbron EL, Towbin JA, Priori SG, Napolitano C, Zhang L, Medina A, Andrews ML, Timothy K. 1999. Comparison of clinical and genetic variables of cardiac events associated with loud noise versus swimming among subjects with the long QT syndrome. Am J Cardiol. 84(8):876–879.PubMedCrossRefGoogle Scholar
- 30.Khositseth A, Ackerman MJ. Clinical evaluation, risk stratification, and management of congenital long QT syndrome. In: Gussak I, Antzelevitch C, eds. Contemporary Cardiology: Cardiac Repolarization: Bridging Basic and Clinical Science. Totowa: Humana; 2003.Google Scholar
- 31.Priori SG, Napolitano C, Memmi M, Colombi B, Drago F, Gasparini M, DeSimone L, Coltorti F, Bloise R, Keegan R, Cruz Filho FE, Vignati G, Benatar A, DeLogu A. 2002. Clinical and molecular characterization of patients with catecholaminergic polymorphic ventricular tachycardia [see comment]. Circulation. 106(1):69–74.PubMedCrossRefGoogle Scholar
- 35.Probst V, Denjoy I, Meregalli PG, Amirault JC, Sacher F, Mansourati J, Babuty D, Villain E, Victor J, Schott JJ, Lupoglazoff JM, Mabo P, Veltmann C, Jesel L, Chevalier P, Clur SA, Haissaguerre M, Wolpert C, Le Marec H, Wilde AA. 2007. Clinical aspects and prognosis of Brugada syndrome in children. Circulation. 115(15):2042–2048.PubMedCrossRefGoogle Scholar
- 36.London B, Michalec M, Mehdi H, Zhu X, Kerchner L, Sanyal S, Viswanathan PC, Pfahnl AE, Shang LL, Madhusudanan M, Baty CJ, Lagana S, Aleong R, Gutmann R, Ackerman MJ, McNamara DM, Weiss R, Dudley SC, Jr. 2007. Mutation in glycerol-3-phosphate dehydrogenase 1-like gene (GPD1-L) decreases cardiac Na+ current and causes inherited arrhythmias. Circulation. 116(20):2260–2268.PubMedCrossRefGoogle Scholar
- 37.Watanabe H, Koopmann T, Le Scouarnec S, Yang T, Ingram C, Schott J, Demolombe S, Probst V, Anselme F, Escande D, Wiesfeld A, Pfeufer A, Kääb S, Wichmann H, Hasdemir C, Aizawa Y, Wilde A, Roden D, Bezzina C. 2008. Sodium channel beta1 subunit mutations associated with Brugada syndrome and cardiac conduction disease in humans. J Clin Invest. 118(6):2260–2268.PubMedGoogle Scholar
- 38.Antzelevitch C, Pollevick GD, Cordeiro JM, Casis O, Sanguinetti MC, Aizawa Y, Guerchicoff A, Pfeiffer R, Oliva A, Wollnik B, Gelber P, Bonaros EP, Jr., Burashnikov E, Wu Y, Sargent JD, Schickel S, Oberheiden R, Bhatia A, Hsu LF, Haissaguerre M, Schimpf R, Borggrefe M, Wolpert C. 2007. Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death. Circulation. 115(4):442–449.PubMedCrossRefGoogle Scholar
- 39.Delpon E, Cordeiro JM, Nunez L, Bloch Thomsen PE, Guerchicoff A, Pollevick GD, Wu Y, Kanters JK, Larsen CT, Burashnikov E, Christiansen M, Antzelevitch C. 2008. Functional effects of KCNE3 mutation and its role in the development of Brugada syndrome. Circ Arrhythm Electrophysiol. 1(3):209–218.PubMedCrossRefGoogle Scholar
- 42.Brugada R, Hong K, Dumaine R, Cordeiro J, Gaita F, Borggrefe M, Menendez TM, Brugada J, Pollevick GD, Wolpert C, Burashnikov E, Matsuo K, Wu YS, Guerchicoff A, Bianchi F, Giustetto C, Schimpf R, Brugada P, Antzelevitch C. 2004. Sudden death associated with short-QT syndrome linked mutations in HERG. Circulation. 109:30–35.PubMedCrossRefGoogle Scholar