Development of a New Method to Prioritise Gene Analysis in Familial Hypertrophic Cardiomyopathy

1. Development of a New Method to Prioritise Gene Analysis in Familial Hypertrophic Cardiomyopathy Jayne Duncan West of Scotland Regional Genetics Service, Glasgow

2. Familial Hypertrophic Cardiomyopathy (FHC) • Autosomal dominant disorder showing variable penetrance and age of onset. • Affects approximately 1/500 adults and is the most common cause of sudden death in young healthy individuals. • So far mutations in over 20 genes have been associated with FHC

3. Primary Clinical Features of FHC • Left ventricular hypertrophy, “a thickening of the tissue due to increased size of the constituent cells”. • Myocyte/myofibrillar disarray caused by the abnormal shapes, intracellular connections and arrangement of the hypertrophic myocytes and fibrosis. 1 http://www.maxshouse.com 2 Arad et al 2002 Hum Mol Genet. 11. (20) 2499-2506

4. Genotype Phenotype Correlation

5. The Heterogeneous Nature of FHC • HCM is caused by dominant mutations in the sarcomeric genes. • de novo mutations occur rarely and account for approximately 10% of cases. • Mutations in the sarcomeric genes account for ~55% of cases of HCM. • Syndromes such as the Glycogen storage disorders and Friedreich ataxia can mimic HCM.

6. Glasgow Linkage Exclusion Analysis Method (GLEAM) • Glasgow Linkage Exclusion Analysis Method (GLEAM) • Novel method to prioritise gene analysis in heterogeneous disorders • A gene is excluded from analysis when affected relatives are oppositely homozygous for SNPs in and around the gene of interest

7. BB AB AA AB BB AB AB AA GLEAM • A and B represent alleles at a susceptibility locus for a dominantly inherited disorder affecting individuals II:2, II:3, III:1 and III4. • Since III:1 has no allele in common with II:3 or III:4 it effectively rules out this locus as being responsible for the disease in this family.

8. Genes analysed in the FHC Project

9. SNP Analysis Platform Sentrix Array Matrix • 96 fibre optic bundles on each plate • Each fibre contains a bead that corresponds to each SNP • Image taken from www.Illumina.com

10. Results- Raw Data Raw data for one patient sample

11. Results- Raw Data AB AA BB Clustered patient SNP data for a single SNP locus

12. Results- Genotype Comparisons

13. Results

14. Results

15. Interesting Case H15.1 H15.4 H15.7 H15.14 H15.15 H15.16 H15.12 TNNI3/ TNNI3/MYBPC3TNNI3TNNI3 TNNI3 TNNI3 MYBPC3MYBPC3

16. Interesting Case • Familial mutation in TNNI3 was not excluded in all affected family members. • Comparisons between H15.1, H15.4 and H15.7 did not exclude MYBPC3. • MYBPC3 was excluded when H15.1, H15.4 and H15.7 were compared against other family members who did not have this mutation. • Testing for the TNNI3 mutation in H15.7 would have been negative and suggested a second mutation prompting further analysis.

17. Conclusions • For all the pedigrees with one known mutation, this gene was not excluded in any of the analyses performed. • More genes tend to be excluded when more distantly related individuals such as first cousins or aunt/niece, nephew pairs are considered, rather than more closely related sibs • GLEAM can be used to determine the order in which genes are sequenced in heterogeneous disorders

18. Acknowledgements • Scottish Health Innovations Ltd • Dr Wai Lee & Dr Stewart Lang, British Heart Foundation, Glasgow Cardiovascular Research Centre, University of Glasgow. • Dr Petros Syrris, Department of Medicine, University College London