The Genetics of Alternating Hemiplegia of Childhood A long and winding road

1. The Genetics of Alternating Hemiplegia of ChildhoodA long and winding road Matthew T. Sweney, MD MS Clinical Instructor, University of Utah AHC Family Meeting 7/22/11

2. Overview  • Introduction to AHC • Significant Familial cases • Early investigation • Comparative Genomic Hybridization • Whole Genome Sequencing

3. Introduction • Initial Characterization • Verret & Steele 1971 • 8 cases linked by hemiparesis and headache • Migraine variant • Disease evolution • Estimated 1-2 affected children per 1 million • Eye movements, focal dystonia • Hemiparesis/plegia, ataxia • Developmental impact

4. Diagnostic Criteria • Onset of symptoms prior to 18 months of age • Repeated attacks of hemiplegia involving either side of the body • Other paroxysmal disturbances, including tonic or dystonic spells, oculomotor abnormalities and autonomic phenomena, during hemiplegic bouts or in isolation • Episodes of bilateral hemiplegia or quadriplegia as generalization of a hemiplegic episode or bilateral from the beginning • Immediate disappearance of symptoms upon sleeping, which later may resume after waking • Evidence of developmental delay and neurologic abnormalities including choreoathetosis, dystonia, or ataxia

5. Introduction • Diagnostic challenge • Relationship to known paroxysmal diseases • Familial Hemiplegic Migraine • Episodic Ataxias • Periodic Paralysis • Relationship to epilepsy • Typical events not epileptic • Suspected epileptic events in ~50% of cases • As yet unknown pathophysiology • Suspected channelopathy

6. University of Utah AHC database • Affected individuals referred by Physicians, Family Support Organizations • Clinical data and DNA/cell line collection via IRB approved protocol since 1999 • Contact with patients by phone/written communication/in-person at regional meetings

7. University of Utah AHC database • Pediatrics, March 2009 • 172 patients consented to enrollment • 103 patients met diagnostic criteria • Largest database of AHC patients in the world • Familial cases • 5 kindreds with multiple children affected • Others reported, however inadequate medical records or no blood specimen available

8. Familial Cases

9. Translocation • T(3;9)(p14.3;q34.3)

10. BAC 370G13 Contig human tear prealbumin AA683210 R52874 KIAA0649 F11681 BAC-T7 BAC-sp6 hNT neuron U46429 (brain) (infant brain) cpG island cos3-T7 24 kb 22.4 kb cos3-T7 5.9 kb KIAA0649 cos27-T3 8.4 kb cos3-T3 cos55-T7 AA778411 cos55-T3 Odorant (fetal heart) binding protein Total length largest contig 83 kb cos55 37 kb LCN1c 26.5 kb fragment with germ cell cDNA AI662518

11. Candidate Genes • Translocation breakpoint • MRPS2, mitochondrial ribosomal protein • KIAA1422 (KCNT1), calcium activated K+ channel, near translocation breakpoint 9q • KIAA0649--Function unknown • Looks promising, right?…

12. Unaffected Carriers

13. Gene Candidates • CACNA1A, Calcium channel associated with FHM, 19p13.2--bridge phenotypes? • ATP1A2, Positive lod score and shared haplotype for K7940; mutations in two families associated with FHM2 phenotype • SCN1A, mutations found in 3 families with familial hemiplegic migraine (FHM3) • SLC1A3-EAAT1, Glutamate transporter.  Joana Jen identified a point mutation in one sporadic affected individual. 

14. More Genes • CACNA1D, Brain expressed calcium channel, near translocation breakpoint 3p • SLC6A11, Distal 3p near breakpoint • ATP2B2, Near breakpoint in K4323 • CACNA1I, Calcium channel, Positive lod in K4323 • In all, from 1999 to 2008, 25 candidate genes screened

15. Comparative Genomic Hybridization • AKA Microarray Analysis • Assesses copy number changes in DNA content • Uses 244,000 known probes • Covers genes and non-coding regions

16. CGH • 10 subjects in small pilot trial • All met classic criteria • Numerous single-probe copy number variations shared across all 10 • No contiguous probe deletion or duplication shared by all subjects • No clear answers revealed

17. Current work • AHC: Pepsi Refresh Grant • $250,000 grant awarded for the purposes of identifying the genetic cause of AHC • 23 samples sent for whole genome sequencing • Sent via ISB to Complete Genomics, Inc • Provides sequenced data and variant reports • Preliminary data in August, 2011, complete analysis may take additional 6-12 months

18. Why is this important? • Sequencing represents the standard by which other modes are judged • Finally the cost of sequencing is practical • The service we use provide both genetic sequencing as well as preliminary statistical analysis • Data will hopefully serve as foundation for therapy or cure

19. Where do we go from here? • Wait for sequencing to be completed • Statistical analysis of the sequencing • Identify if it is one gene or combination of genes • Identify the function of those gene(s) and model them • Once the function is delineated, identify ways to modify/improve it

20. Conclusions • Complicated, rare disease • Highlights the rationally haphazard approach in a gene hunt • Exemplifies the challenges present with under-recognized disease, underfunded research, understaffed workforce • Presents great opportunity to make an impact

21. Acknowledgments • Kathryn J. Swoboda, MD • Pediatric Motor Disorders Group: Sandy Reyna, MD, Aga Lewelt, MD, Abby Smart, RN • Fran Filloux, MD, Stefan Pulst, MD, Art Brothman, PhD • Alternating Hemiplegia of Childhood Foundation