Download Mutations in gamma adducin lead to an inherited

The Genomics of Cerebral Palsy:
genetic insights beg new questions
of a once well-understood disease
Michael Kruer, MD
Sanford Children’s
Health Research Center
Conflicts of Interest
• No disclosures
CP definition
• “Cerebral palsy (CP) describes a group of permanent disorders
of the development of movement and posture, causing
activity limitation, that are attributed to nonprogressive
disturbances that occurred in the developing fetal or infant
brain.”1
1 Rosenbaum, et al. DMCN 2007 109:8-14.
Forms of cerebral palsy
• Spastic
– Hemiplegic
– Paraplegic/Diplegic
– Quadriplegic
• Dyskinetic
– Dystonic
– Choreoathetotic
• Ataxic
• Hypotonic
The quandry of CP with normal MRI
Cystic leukomalacia
In utero stroke
Do single gene defects
causing CP exist?
• Not related to major cortical malformation,
genetic syndrome, metabolic disorder, or
thrombophilia
• Typically spastic diplegia or quadriplegia
• Distinct from hereditary spastic paraplegia?
Many patients with spastic diplegia have a normal MRI (41.9%)
Those who do have abnormal MRIs often have nonspecific findings
“These findings suggest unknown pathophysiologic processes”
A single gene form of CP
So when does rare = common?
Does CP mirror other common neurodevelopmental
disorders such as intellectual disability or autism?
Do hundreds of CP genes exist?
Bedside to bench…
Familial cerebral palsy
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4 affected children born to Jordanian parents
Early hypotonia, motor and language delay
Spastic diplegia ----> spastic quadriplegia
Borderline IQ ----> moderate ID
One child had epilepsy
Subtle white matter anomalies
Next steps
• Extensive workup, including muscle and skin
biopsy, was normal
– Patient-derived fibroblasts were available
• Family structure facilitated a homozygosity
mapping/exome sequencing approach
Identity by Descent
Potential relevance
- Axon outgrowth & connectivity
- Synaptic maintenance
- Neuronal migration
Adducin domains
Mutation of a highly conserved residue could
affect oligomerization
Experimental validation is crucial
Impaired colocalization in ADD3 mutant cells
ADD3 p.G367D fibroblasts demonstrate unchecked
actin polymerization indicative of
impaired actin capping
ADD p.G367D fibroblasts show increased proliferation and
migration consistent with impaired actin capping
Drosophila hts mutants recapitulate key
features of human phenotype
Molecular basis of
genetic CP paradigm
Impaired actin
capping
Excessive actin
polymerization
Abnormal
neuronal
migration
Heterotopias
Aberrant
neurite
extension
Abnormal
synaptic
connectivity
Abnormal
neuronal
networks
Spastic
cerebral
palsy
Intellectual
disability
A common molecular pathogenesis?
• Other “CP genes”
– KANK1: actin-capping ankyrin-repeat domain protein
– Adaptor protein-4?
– Synaptic role?
KANK1
F-actin
nucleus
???
KANK1
Adducin
G-actin
Adducin
Initial Conclusions
• ADD3 mutations impair actin capping and lead
to abnormal cell migration, synaptic
connectivity and a cerebral palsy phenotype
• Several ‘CP genes’ may intersect in a common
pathway
• Many additional single gene causes of CP
likely await discovery
MORE QUESTIONS
What distinguishes inherited CP from
hereditary spastic paraplegia?
• CP, by nature, is a nonprogressive disorder
while HSP is a progressive disease
• Clinical teaching has held that patients with
CP are likely to respond better to surgery,
Botox, and medical interventions
• However, little literature supports this notion
Can actin-capping defects be rescued?
Misakinolide A
Toxicity profile?
Can abnormal connectivity be rescued?
Animal model
• Can the defects seen in flies lacking adducin
be rescued by misA treatment?
Untreated
Treated
Next steps: How common are
genetic forms of CP?
• Cerebral Palsy Genetics collaborative
network
Study outline
Multiinstitution
collaborative
100 sporadic CP patients
Idiopathic CP
No vascular lesions
No major malformations
Exome
sequencing
Data mining/
bioinformatic
analysis
Participation
Centralized IRB
Potential participants identified by collaborating clinician
Study flyer given
Interested family contacts CPGC research coordinator by email
Study coordinator explains study purpose & protocol
Consent forms and buccal swab kits sent to family’s home
Samples & signed consents received at Sanford Research
Ongoing gene discovery studies
• Lethargy, hypotonia, poor feeding
• Lactic acidosis
• Renal tubular defect
Ultrasounds from 26 week estimated
gestational age infant
MRI from term sister
Same periventricular cystic leukomalacia
Control
Patient
Spastic diplegic CP
Acknowledgements
Collaborators
• Doris Kretzschmar
• Patrick Chinnery
• Bob Steiner
• Randy Woltjer
• Henry Houlden
• Catherine Mooney
• Coro Paisan-Ruiz
• Peter Blasco
• Barry Russman
• Mark Merkens
Funding
• NIH NINDS
• American Academy of
Neurology
• American Academy of
Cerebral Palsy &
Developmental Medicine
• Child Neurology
Foundation
CP Genetics Collaborative Network
Collaborators
• Donna Hurley
• Deb Gaebler
• Barry Russman
• Jilda Vargus-Adams
• Peter Blasco
• Tim Feyma
• Ann Tilton
• Kazuhiro Haginoya
• Dinah Reddihough
KRUER LAB
Contact: Michael Kruer
[email protected]