Genetics of Congenital Heart Disease

1. Genetics of Congenital Heart Disease 张咸宁 zhangxianning@zju.edu.cn Tel：13105819271; 88208367 Office: A705, Research Building 2013/03

2. Required Reading Thompson &Thompson Genetics in Medicine, 7th Ed （双语版，2009） ● Pages 91-92、168-169、356

3. Learning Objectives To recognize familial patterns of CHD To understand developmental mechanisms of CHD To see CHDs as examples of the larger group of common disorders with common complex inheritance involving Single genes Multiple genes Environmental influences

4. Overview Introduction to Congenital Heart Disease (CHD) Developmental Mechanisms Flow Lesions Problems in Cell Migration Problems in Cell Death Abnormalities in Extracellular Matrix Abnormalities in Targeted Growth Summary

5. Introduction to CHD Relatively common birth defect Liveborn infants 4-8/1 000 Stillborns 10× higher or 8% Miscarriages 15% in abortuses <24 weeks gestation

6. Introduction to CHD Variety of causes Single gene Chromosomal Teratogen exposures Maternal rubella infection Gestational diabetes mellitus

7. Maternal Infections Rubella: 35% affected Maternal Diseases Diabetes Mellitus: 3-5% Maternal PKU: 10% Teratogenic Substances Alcohol: 25-35% Dilantin（苯妥英）: 2-3% Environmental Component

8. Gross Chromosomal Defects 5-8% of Defects Examples Trisomy 21: 35-50% Trisomy 18: 99% Turner syndrome: 20% Single-Gene Defects 3% of Defects Genetic Component

9. Familial Patterns of Recurrence CHD recurrence in a family Affected individuals may not have identical anatomical heart abnormality Will have lesions representing similarity in the developmental mechanism Should look for abnormalities outside of the cardiovascular system May indicate a syndromic association with CHD

10. Developmental Mechanisms Flow Lesions Problems in Cell Migration Problems in Cell Death Abnormalities in Extracellular Matrix Abnormalities in Targeted Growth

12. Is Isolated CHD a Multifactorial Trait? Table 8-12: Population Incidence and Recurrence Risks for Various Flow Lesions VSD = Ventricular Septal Defect PDA = Patent Ductus Arteriosus ASD = Atrial Septal Defect AS = Aortic Stenosis

13. Is Isolated CHD a Multifactorial Trait? For these flow lesions Sib relative risk ratio (λsib) Support familial aggregation Where genetic mutation not known Use empiric risk factors to counsel first degree relatives Rapid decrease in risk for second and third degree relatives to not much higher than population risks For families with CHD other than flow lesions Reassure that recurrence risk is no greater than population risk Prenatal ultrasound can be used as part of counseling and often reassurance before birth

14. Flow Lesions Large category of CHDs Approximately 50% of all CHDs Up to 25% of flow lesion CHDs, particularly tetralogy of Fallot, have del22q11.2 DiGeorge syndrome Velocardiofacial syndrome Conotruncal anomaly face syndrome

15. del22q11.2 Syndromes Autosomal dominant Variable expressivity Deletion of approximately 3 Mb Caused by homologous recombination of low copy repeat sequences One of the most common cytogenetic deletions with a significant phenotype 1 per 2 000 – 4 000 live births

16. 22q11.2 Rearrangements Fig 6-9

17. del22q11.2 Syndromes Phenotypes may include CHD Craniofacial abnormalities Mental retardation/developmental delay Reduced circulating lymphocytes Hypocalcemia Schizophrenia

18. del22q11.2 and CHD Responsible for between 5% and 12.5% of CHDs Particularly common in certain CHDs >40% of patients with tetralogy of Fallot (TOF) and pulmonary atresia (PA) >60% of patients with TOF and absent pulmonary valve

19. DGS TDR(Typically Deleted Region) 3 Mb deletion Loss of approximately 30 genes Smaller 1.5 Mb deletion Seen in approximately 10% of patients TBX1 maps in DGS TDR Encodes transcription factor involved in pharyngeal arch development Haploinsufficiency implicated in DGS Mutated in patients with similar phenotype who do not have del22q11.2

20. Apoptosis and CHD TBX1 may be involved in apoptosis, a mechanism known to be involved in normal cardiac and lymphocyte development Foxp1 in mice Required for remodeling of endocardial cushions (portions of ventricular septum and cardiac outflow tract) To position aortic and pulmonary vessels normally by eliminating certain cells to shift the cushions’ positions Apoptosis occurs during immune system development To eliminate lymphocytic lineages that react to self Required for protection against autoimmune disease

21. Apoptosis and CHD If TBX1 causes the conotruncal defects (e.g. TOF) associated with del22q11.2, and if the mechanism is apoptosis, then what does that do to our “developmental mechanisms” outlined at the beginning del22q11.2 causes the largest proportion of flow lesions, but may be a problem in cell death

22. 4-m.o. Female Infant CHF from a Large VSD Dysmorphic Appearance Family History: Sib and Half-Sib with CHD Mother with Multiple Psychiatric Admissions Case #1 Truncus Arteriosus TOF VSD

23. DiGeorge (not DiGeorge’s) Syndrome Features Include: Cardiac: Conotruncal Defects Immunologic: Thymic Aplasia or Hypoplasia Hypocalcemia: Parathyroid Absence or Hypoplasia Dysmorphism: Hypertelorism, Short Philtrum, Cupid’s Bow Mouth, Ear Anomalies DiGeorge Syndrome

24. Features Include: Cardiac: VSD, Tetralogy of Fallot, Rt. Aortic Arch Cleft Palate: Overt or Submucosal Development Delay: Mild-to-Moderate, esp. Speech Dysmorphisms: Prominent Nose, Abnormal Ears, Abundant Hair, Tapered Fingers VeloCardioFacial (VCF) Syndrome

25. VCF/DG SYNDROMESClinical Overlap Cleft Palate Dev. Delay VCF Facies Cleft Palate Dev. Delay DGS CHD Dev. Delay VCF Facies

27. Problems in Cell Migration:Patent Ductus Arteriosus (PDA) • 1 in 2 000 Fullterm Infants • 10% of CHD • 2:1 Female to Male Ratio • Multifactorial Etiology: Genes and Environment

28. Familial PDA 2-y.o. Palestinian Boy Patent Ductus Arteriosus Positive Family History PDA PDA

29. Neural Crest Cell Migration and Cardiac Development

30. Cardiac GeneticsPopulation Perspective Developing Innovative Therapies Postnatal Interventions Marfan Syndrome: Anti-TGF Prenatal Interventions Folate Improving Clinical Trials Research Cardiology Emulating Heme/Onc Primary Endpoints - Function, Not Survival Better Statistical Power

32. First, exome-centered and whole-genome next-generation sequencing • Second, epigenetics and transcriptomics • Third, systems biology

33. GWAS: the genetic variants identified often explain 10% of the variation in a trait or disease!

34. Epigenetics and Transcriptomics • Research is increasingly acknowledging that static DNA sequence variation explains only a fraction of the inherited phenotype. Therefore, we expect that multiple epigenetic and gene expression signatures will be related to CVD in experimental and clinical settings.

35. Complex relationships between the genome, epigenetic and transcriptional regulations, the proteome, and the metabolome that produce CVD phenotypes.

36. Summary: CHD Relatively common birth defect 4-8/1 000 live births Familial CHD May not have identical anatomic abnormality Variety of developmental mechanisms Undergoing revision as we understand molecular pathogenesis

37. CHD Recurrence risk If familial, identify inheritance pattern If not familial, use empiric risk data del22q11.2 is a common cause of CHD Up to 25% of flow lesions Flow lesions represent 50% of all CHD Therefore, 12.5% of all CHD