The Genetics of Alternating Hemiplegia of Childhood

A long and winding road

The Genetics of Alternating Hemiplegia of Childhood

A long and winding road

Matthew T. Sweney, MD MS

Clinical Instructor, University of Utah

AHC Family Meeting

7/22/11

Matthew T. Sweney, MD MS

Clinical Instructor, University of Utah

AHC Family Meeting

7/22/11

Overview Overview 

Introduction to AHC Significant Familial cases Early investigation Comparative Genomic Hybridization Whole Genome Sequencing

Introduction to AHC Significant Familial cases Early investigation Comparative Genomic Hybridization Whole Genome Sequencing

IntroductionIntroduction 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

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

Diagnostic CriteriaDiagnostic Criteria1. Onset of symptoms prior to 18 months of age2. Repeated attacks of hemiplegia involving either side of the

body3. Other paroxysmal disturbances, including tonic or dystonic

spells, oculomotor abnormalities and autonomic phenomena, during hemiplegic bouts or in isolation

4. Episodes of bilateral hemiplegia or quadriplegia as generalization of a hemiplegic episode or bilateral from the beginning

5. Immediate disappearance of symptoms upon sleeping, which later may resume after waking

6. Evidence of developmental delay and neurologic abnormalities including choreoathetosis, dystonia, or ataxia

1. Onset of symptoms prior to 18 months of age2. Repeated attacks of hemiplegia involving either side of the

body3. Other paroxysmal disturbances, including tonic or dystonic

spells, oculomotor abnormalities and autonomic phenomena, during hemiplegic bouts or in isolation

4. Episodes of bilateral hemiplegia or quadriplegia as generalization of a hemiplegic episode or bilateral from the beginning

5. Immediate disappearance of symptoms upon sleeping, which later may resume after waking

6. Evidence of developmental delay and neurologic abnormalities including choreoathetosis, dystonia, or ataxia

IntroductionIntroduction 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

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

University of Utah AHC databaseUniversity 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

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

University of Utah AHC database 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

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

Familial CasesFamilial Cases

TranslocationTranslocation

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

BAC 370G13 Contig

cos3-T75.9 kb

cos27-T38.4 kb

AA683210 R52874 KIAA0649 F11681 BAC-T7 BAC-sp6hNT neuron U46429 (brain) (infant brain) cpG island cos3-T7 24 kb 22.4 kb

cos3-T3 cos55-T7 AA778411 cos55-T3 Odorant (fetal heart) binding protein

Total length largest contig 83 kb cos55 37 kb

KIAA0649

LCN1c

human tearprealbumin

26.5 kb fragment with germ cell cDNA AI662518

Candidate GenesCandidate Genes

Translocation breakpoint MRPS2, mitochondrial ribosomal protein KIAA1422 (KCNT1), calcium activated K+

channel, near translocation breakpoint 9q KIAA0649--Function unknown Looks promising, right?…

Translocation breakpoint MRPS2, mitochondrial ribosomal protein KIAA1422 (KCNT1), calcium activated K+

channel, near translocation breakpoint 9q KIAA0649--Function unknown Looks promising, right?…

Unaffected CarriersUnaffected Carriers

Gene CandidatesGene 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. 

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. 

More GenesMore 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

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

Comparative Genomic HybridizationComparative Genomic Hybridization

AKA Microarray Analysis

Assesses copy number changes in DNA content

Uses 244,000 known probes

Covers genes and non-coding regions

AKA Microarray Analysis

Assesses copy number changes in DNA content

Uses 244,000 known probes

Covers genes and non-coding regions

CGHCGH

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

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

Current workCurrent 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

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

Why is this important?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

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

Where do we go from here?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

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

ConclusionsConclusions

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

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

AcknowledgmentsAcknowledgments

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

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