the fmr1 disorders (fragile x syndrome, etc). mary beth busby founding board member of the fragile x...
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The FMR1 disorders(Fragile X syndrome, etc)
The FMR1 disorders(Fragile X syndrome, etc)
• Mary Beth Busbyfounding board member of the Fragile X Research Foundation (FRAXA)
• Walter KaufmannDirector, Center for Genetic Disorders of Cognition and Behavior, Kennedy Krieger Institute, The Johns Hopkins University
• Karen UsdinChief, Gene Structure and Disease SectionLMCB, NIDDK
Understanding the molecular Understanding the molecular basis of the FMR1 gene basis of the FMR1 gene
disordersdisorders
Karen UsdinKaren Usdin
5’ UTR5’ UTR
exon 1exon 1 intron 1intron 1
(CGG)n(CGG)n
promotepromoterr
X chromosome
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FXPOI FXPOI
male
female
The Repeat Expansion Diseases
Myotonic Myotonic dystrophdystroph
yytype 1type 1
Myotonic Myotonic dystrophdystroph
yytype 1type 1
Also: SCA 8, SCA12, and HDL2Also: SCA 8, SCA12, and HDL2Also: SCA 8, SCA12, and HDL2Also: SCA 8, SCA12, and HDL2
FMR1 FMR1 disordersdisorders
FMR1 FMR1 disordersdisorders
Friedreich Friedreich ataxiaataxia
Friedreich Friedreich ataxiaataxia
Haw River SyndromeHaw River Syndrome(DRPLA)(DRPLA)
Haw River SyndromeHaw River Syndrome(DRPLA)(DRPLA)
HuntingtoHuntington diseasen diseaseHuntingtoHuntington diseasen disease
SCA 1, 2, 6, 7SCA 1, 2, 6, 7SCA 1, 2, 6, 7SCA 1, 2, 6, 7
Kennedy DiseaseKennedy Disease(SBMA)(SBMA)
Kennedy DiseaseKennedy Disease(SBMA)(SBMA)
Progressive Progressive myoclonus myoclonus epilepsyepilepsy
Progressive Progressive myoclonus myoclonus epilepsyepilepsy
FRAXE MRFRAXE MRFRAXE MRFRAXE MR
SCA10SCA10SCA10SCA10 Myotonic Myotonic dystrophydystrophy
type 2type 2
Myotonic Myotonic dystrophydystrophy
type 2type 2
ORPromoter 5’ UTR ORF 3’ UTRIntron
(CGG)n (CTG)n(CAG)n(GAA)n (ATTCT)n(C4GC4GCG)n (CCTG)n
gametogenesis
Premutation symptoms result from RNA “toxicity”
Premutation symptoms result from RNA “toxicity”
• The RNA is somehow deleterious
• the CGG-repeats may• trigger deleterious processes • sequester proteins that are
important for normal neuronal and ovarian function
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RNA “toxicity” hypothesisRNA “toxicity” hypothesis
• The RNA is somehow deleterious
• the CGG-repeats may initiate or trigger deleterious processes
• the CGG-repeats may sequester proteins that are important for normal neuronal and ovarian function
RNA interferenceRNA interference
Hannon (2002)
SK cells
DAPI
lamin
merge
SK cells+CGG88
Is FXTAS a laminopathy?Is FXTAS a laminopathy?
• mutations in Lamin A/C are associated with one form of Charcot-Marie-Tooth disease, a neurological disorder
• other mutations in Lamin A/C result in premature aging
Gene silencingin mammals
DNA methylation
Histone modifications
Science, 1991
5-azadeoxycytidine
What does FMRP do?What does FMRP do?
•learning difficulties•macroorchidism•altered circadian rhythms•rapid early growth rate•audiogenic seizures•anxiety
QuickTime™ and aVC Coding
QuickTime™ and aVC Coding
QuickTime™ and aVC Coding
QuickTime™ and aVC Coding
Qin and Beebe-Smith (NIMH)
WT
KO
FMRP structureFMRP structure
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NDF
RNAs bound by FMRPRNAs bound by FMRP
• FMR1• Glucocorticoid receptor• GABAA receptor subunits• CAMKIIα• MAP1B• Rac1• Calbindin• Vimentin• etc, etc
protein product
Protein gel
- FMRP
FMRPI3
04N
Increased rates of cerebral glucose metabolism in a mouse model of fragile X mental retardation
Increased rates of cerebral glucose metabolism in a mouse model of fragile X mental retardation
Qin, Kang, and Beebe Smith (2002) (NIMH)
WT
KO
Nissl staining [14C] DG
Results of “fishing” for FMRP interacting proteins
Results of “fishing” for FMRP interacting proteins
• FXR1P• FXR2P• CYFIP1 and CYFIP2• Poly(A)-binding protein• eIF2C2/AGO1 • Dicer • kinesin heavy chain
RNA interferenceRNA interference
Hannon (2002)
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axon
dendritesynapse
Grazyna Gorny
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Synaptic transmissionSynaptic transmission
FXS Un Dendritic Spine Structural Anomalies in Fragile-X Mental Retardation Syndrome
Irwin, Galvez and William T. Greenough
Cerebral Cortex (2000)
Results of “fishing” for FMRP interacting proteins
Results of “fishing” for FMRP interacting proteins
• FXR1P• FXR2P• CYFIP1 and CYFIP2• Poly(A)-binding protein• eIF2C2/AGO1 • Dicer • kinesin heavy chain
FMRP
RISC
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mGluR5 receptor
WTFX
MG+/-
FX/MG+/-
MinocyclineMinocycline
Metalloproteinase-9 (MMP-9)Metalloproteinase-9 (MMP-9)
Take home messagesTake home messages
• FXTAS and FXPOI result from repeat-induced hyperexpression of the FMR1 gene and the deleterious effects of high levels of CGG-repeat containing mRNA.
• FXS results from repeat-induced gene silencing.• silencing leads to a deficiency of FMRP, a protein
important for the regulation of translation in the synapses of neurons
• the resultant abnormal expression of proteins like mGluR5, GSK-3, GABAA and MMP-9 results in the symptoms of FXS
• normalizing expression of these proteins may provide targeted approaches to the treatment of FXS.
