1. CAN GENETIC STUDIES HELP TO BETTER UNDERSTAND & TO REDUCE RISK FOR SIDS? Carl E. Hunt, MD First Candle Symposium March 24, 2009

2. OBJECTIVES Review Genetic Risk Factors for sudden, unexpected deaths in infancy (SUDI) Review Genetic Risk Factors for sudden, unexpected deaths in infancy (SUDI) Relation of genetic risk factors to environmental risk factors Relation of genetic risk factors to environmental risk factors Gene-environmentGene-environment Final Perspectives Final Perspectives How genetic research related to SUDI does help usHow genetic research related to SUDI does help us LimitationsLimitations Next stepsNext steps

3. GENETIC RISK FACTORS

4. 26 Genes For Which Distribution of polymorphisms Differs in SIDS* Cardiac Channelopathies: EIGHT Cardiac Channelopathies: EIGHT Serotonin (5-HT): THREE Serotonin (5-HT): THREE Autonomic Nervous System Autonomic Nervous System Development EIGHT Infection & Inflammation: SIX Infection & Inflammation: SIX Energy Production: ONE Energy Production: ONE TOTAL 26 *Hunt CE, Hauck FR. SIDS: Gene-environment interactions, in Clinical Care in Inherited Syndromes, ed. R Brugada, J Brugada, P Brugada. Springer- Verlag London Ltd. Guilford, UK, in press.

5. CARDIAC CHANNELOPATHIES (8) (Arrhythmia Susceptibility Genes) Long QT Syndrome (LQTS), SQTS Long QT Syndrome (LQTS), SQTS Sodium channel (SCN5A)Sodium channel (SCN5A) Sodium channel-interacting proteinsSodium channel-interacting proteins CAV3 CAV3 SCN4B SCN4B GPD1-L GPD1-L Potassium channel (KCNQ1,KCNH2, KCNE2)Potassium channel (KCNQ1,KCNH2, KCNE2) RyR2-encoded cardiac ryanodine receptor ( CPVT1 )RyR2-encoded cardiac ryanodine receptor ( CPVT1 ) Normal resting ECG Normal resting ECG

6. Genetic Risk Factors, cont. Serotonin (5-HT) (3) Important neurotransmitter Important neurotransmitter Polymorphisms in 3 genes: Polymorphisms in 3 genes: 5-HT transporter protein (5-HTT)5-HT transporter protein (5-HTT) Intron 2 of SLC6A4Intron 2 of SLC6A4 VNTR polymorphism VNTR polymorphism 5-HT FEV gene5-HT FEV gene

7. Genetic Risk Factors, cont. Autonomic Nervous System Development (8) Paired-like homeobox 2A PHOX2A)Paired-like homeobox 2A PHOX2A) PHOX2BPHOX2B Rearranged during transfection factor (RET)Rearranged during transfection factor (RET) Endothelin converting enzyme-1 (ECE1)Endothelin converting enzyme-1 (ECE1) T-cell leukemia homeobox (TLX3)T-cell leukemia homeobox (TLX3) Engrailed-1 (EN 1)Engrailed-1 (EN 1) Tyrosine hydroxylase (THO1)Tyrosine hydroxylase (THO1) Monoamine oxidase A (MAOA)Monoamine oxidase A (MAOA)

8. Genetic Risk Factors, cont. Infection & Inflammation (6) ( Activated Immune System) Complement C4A (partial deletion) Complement C4A (partial deletion) Complement C4B (partial deletion) Complement C4B (partial deletion) Interleukin-10 (IL 10) (low levels) Interleukin-10 (IL 10) (low levels) IL-6* IL-6* Mixed results, but multiple polymorphismsMixed results, but multiple polymorphisms VEGF* (Dashash M. Human Immunol 2006) VEGF* (Dashash M. Human Immunol 2006) TNF-alpha (Ferrante L, et al. Human Immunol 2008) TNF-alpha (Ferrante L, et al. Human Immunol 2008) *Increased levels in CSF in SIDS victims

9. DEFINITIONS GENOTYPE GENOTYPE Genetic make-up, with various combinations of polymorphismsGenetic make-up, with various combinations of polymorphisms PHENOTYPE PHENOTYPE Clinical manifestation of a genotype or combined manifestation of several different genotypesClinical manifestation of a genotype or combined manifestation of several different genotypes May not be evident on routine physical examination or routine clinical testingMay not be evident on routine physical examination or routine clinical testing

10. PHENOTYPES Cardiac Channelopathies Phenotype presumed, but not confirmed Phenotype presumed, but not confirmed May be concealed (latent)* and require provocation May be concealed (latent)* and require provocation Sympathetic stressSympathetic stress Epinephrine infusion** Epinephrine infusion** Sleep Sleep AcidosisAcidosis HypoxiaHypoxia *Plant LD et al. JCI 2006; Tester DJ, et al. Heart Rhythm 2007 *Plant LD et al. JCI 2006; Tester DJ, et al. Heart Rhythm 2007 **Ackerman MJ. Heart Rhythm 2008

11. CARDIAC CHANNELOPATHIES Screening PRO PRO Could theoretically “prevent” 5-10 % of SIDSCould theoretically “prevent” 5-10 % of SIDS CON (problems to overcome) CON (problems to overcome) Cost of testingCost of testing Accuracy of interpretationAccuracy of interpretation Frequency of false negative ECGsFrequency of false negative ECGs Managing of false positive ECGsManaging of false positive ECGs May raise socioeconomic and psychosocial problems May raise socioeconomic and psychosocial problems Effectiveness and safety of treatment for those positive with LQTSEffectiveness and safety of treatment for those positive with LQTS

12. Phenotypes, cont. Serotonin (5-HT) No matched phenotypes and genotypes No matched phenotypes and genotypes Potential phenotypes Potential phenotypes Cardiorespiratory regulationCardiorespiratory regulation 5-HTT knockout mice*: reduced ventilatory response to CO 2 (especially males) 5-HTT knockout mice*: reduced ventilatory response to CO 2 (especially males) Other autonomic regulationOther autonomic regulation Other…..?Other…..? Li A, Nattie E. J Physiol 2008

13. Phenotypes, cont. Autonomic Nervous System Polymorphisms No matched phenotypes/genotypes No matched phenotypes/genotypes Consistent with Consistent with Clinical studies (limited) in young infants later dying of SIDSClinical studies (limited) in young infants later dying of SIDS Clinical studies in ALTE and preterm infantsClinical studies in ALTE and preterm infants Postmortem studies indicating abnormalities in CNS areas involved with autonomic and cardio-respiratory regulation*Postmortem studies indicating abnormalities in CNS areas involved with autonomic and cardio-respiratory regulation* *Morley ME et al. Am J Med Genetics Part A. 2008

14. Phenotypes, cont. Infection & Inflammation No matched phenotypes/genotypes No matched phenotypes/genotypes Consistent with epidemiology studies indicating increased frequency of infections in SIDS infants Consistent with epidemiology studies indicating increased frequency of infections in SIDS infants Identified polymorphisms: Identified polymorphisms: Gain-of-function in pro-inflammatory cytokinesGain-of-function in pro-inflammatory cytokines Loss-of-function in anti-inflammatory cytokinesLoss-of-function in anti-inflammatory cytokines

15. GENE INTERACTIONS

16. Gene Interactions Gene Interactions Gene-environment Gene-environment “Genetics loads the gun and environment pulls the trigger*”“Genetics loads the gun and environment pulls the trigger*” “Genes predispose, environment disposes”“Genes predispose, environment disposes” *Dr. Francis Collins, Past Director, National Human Genome Research Institute, NIH

17. Smoking Cardiac ion channel polymorphism ANS polymorphism 5-HTT polymorphism Complement or Interleukin polymorphism Soft bedding Prone or side sleeping Environmental risk factorsGenetic risk factors Prematurity Sudden Infant Death Impaired autonomic regulation and arousal Hunt & Hauck, in press

18. FUTURE DIRECTIONS Research to Practice (Translation) Antemortem phenotyping essential Antemortem phenotyping essential ScreeningScreening InterventionIntervention Broaden our focus to include other sudden death groups Broaden our focus to include other sudden death groups Sudden Intrauterine Unexplained Death (SIUD)Sudden Intrauterine Unexplained Death (SIUD) 1-2% of pregnancies end in stillbirth 1-2% of pregnancies end in stillbirth Many shared features with SUDI and SIDS Many shared features with SUDI and SIDS Sudden Unexplained Death in Childhood (SUDC)Sudden Unexplained Death in Childhood (SUDC) 0.013 per 1 000 live births 0.013 per 1 000 live births Sudden unexplained death in epilepsySudden unexplained death in epilepsy

19. SUMMARY The “Take Home” Message on Genetic Research Provides biologic mechanisms for SUDI when no “apparent” explanation at autopsy Provides biologic mechanisms for SUDI when no “apparent” explanation at autopsy Genetic autopsies not yet feasibleGenetic autopsies not yet feasible Especially important in those rare occurrences of multiple SUDI in families Especially important in those rare occurrences of multiple SUDI in families Helps to understand how environmental risk factors may lead to SUDI in infants genetically predisposed Helps to understand how environmental risk factors may lead to SUDI in infants genetically predisposed MAJOR CHALLENGE: MAJOR CHALLENGE: Not yet feasible to recognize in early infancy which infants are genetically predisposed to SUDI if & when confronted with relevant environmental risksNot yet feasible to recognize in early infancy which infants are genetically predisposed to SUDI if & when confronted with relevant environmental risks

20. SUMMARY, cont. The “Take Home” Message on Genetic Research SUDI is a complex disorder SUDI is a complex disorder No single causeNo single cause Complex interactions between genetic and environmental risk factorComplex interactions between genetic and environmental risk factor No immediate help for families No immediate help for families Highlights the importance of minimizing environmental risk factors that are modifiableHighlights the importance of minimizing environmental risk factors that are modifiable Expanding knowledge of genetic risk factors will progressively lead to improved understanding regarding potential strategies for clinical testing and (ultimately) intervention Expanding knowledge of genetic risk factors will progressively lead to improved understanding regarding potential strategies for clinical testing and (ultimately) intervention