Preview:
Citation preview
- 1. Fragile X Syndrome Some Recent Advances Dr Khalid Mansour
Priory Cefn Carnau Roger Ballen 1993: Dresie and Casie
- 2. Introduction: X-Linked LD
- 3. FXS: X-Linked LD (Lubs et al, 2012) LD: 23% of the
population in the industrialized world (Male to female ratio: 1.3 :
1) X-Linked LD: 5%10% of LD in males. FXS: 50% of X-linked LD.
(Rousseau et al., 1995). 160 X-Linked LD disorders: 102 genes, 81
syndromal & 35 non-syndromal; 78 mapped. 120 known fragile
sites in the human genome > 6 sites on X chromosome > 3
linked to LD (Lukusa & Fryns, 2008). FXS-A = FSX = Martin-Bell
syndrome: Band Xq27.3. > CGG repeats expansion > Gene (FMR1
& FMR4) > Protein (FMRP) > classical FXS FXS-E = FRAXE:
(Gcz 2000) Band Xq27 > CCG repeats expansion > Gene (FMR2
& FMR3) (synonym AFF2) > Protein (???) > non-syndromic
X-linked LD FXS-F = FRAXF: Band Xq28 > CGG repeats expansion
> Gene (???) > Protein (???) > no clear phenotype has been
established.
- 5. FXS: History
- 6. FXS: History: 1 1938: Lionel Penrose first observed that
more males than females in the population have LD (1.25:1) > X
linked. 1943: Martin and Bell: described a described a family with
11 members with X-linked LD (fragile x symptoms) although they did
not know the cause > Martin-Bell Syndrome. 1953: Watson &
Crick > DNA structure. 1969: Herbert Lubs: the first one to see
the "marker X chromosome" in LD patients. 1970: Frederick Hecht:
coined the term "fragile site > FXS. 1977: Grant Sutherland >
Folate Deficient Medium 199 >specific FXS test JP Martin H
Lubs
- 7. FXS: History: 2 1991: Verkerk: FMR1 gene > FMRP 1991:
Kerr et al > Nonspecific X Linked Mental Retardation (XLMR).
1993: Ashley et al > Hyper-methylation > silencing FMR1 gene
1990s: S Warren & Colleagues > FMRP is a selective
(suppressant) mRNA-binding protein in dendrites. 1994: Bakker et al
> FMR1-KO Mice model generated. 1998: Murray et al > fragile
X- associated Premature Ovarian Failure.(also called FXPOI) S
Warren
- 8. 2001: Hagerman et al > Fragile X-associated Tremor/Ataxia
Syndrome (FXTAS) 2002: Huber et al > mGluR-LTD exaggerated in
FMR1-KO Mice 2004: Bear et al > mGluR theory of FXS. 2005: Yan
et al > MPEP improves FXS in animals. 2009: Clinical trials in
humans. FXS: History: 3 Randi J. Hagerman
- 9. FXS: Common Features
- 10. FXS: Common Physical Features Elongated face & Broad
forehead Large, prominent ears High arched palate Prominent jaw,
Dental crowding Macro-orchidism (post-pubertal) Strabismus (squint)
Murmur, Mitral valve prolapse, cardiomegaly, dilation of aorta
Hypotonia & joint laxity Flat feet, Hollow chest, Scoliosis
Michael Phelps
- 11. FXS: Behavioural Symptoms LD (100%) (IQ: 35-70): with
aging. ASD (50 60%) ADHD (30 60%) Epilepsy (5 20%) (mostly TLE) DSH
(10 30%) Aggression (15 35%) Prader-Willi phenotype. Sensory
processing disorder. Psychosis Speech abnormalities Motor
abnormalities
- 12. FXS: Statistics
- 13. FXS: The most common inherited LD (Paluszkiewicz et al,
2011). 10% of undiagnosed male LD cases 3% of undiagnosed female LD
cases The most leading genetic cause of autism (Paluszkiewicz et
al, 2011). Second most common cause of LD after Trisomy 21 (Down
Syn.) (Rousseau et al., 1995). FXS related milder problems (e.g.
dyscalculia, dyslexia, social phobia, and ADHD) may be more common
than FXS related LD (Hagerman et al, 2010) Fragile X Syndrome:
Statistics Medscape reference 2013
- 14. Statistics: USA Medscape reference 2013 Male FXS: 1 in
2500-4000. Male carriers: 1 in 250-800 Female FXS: 1 in 7000-8000.
Female carriers: 1 in 130-250 Females with FXS: less LD and less
physical characteristics. Males with FXS: more likely to be
sensitive to environmental factors. Mortality rate: not
affected
- 15. FXS: Aetiology
- 16. FXS: Aetiology Medscape reference 2013 FXS Chromosomes >
constriction of band Xq27.3. > site of Fragile X Mental
Retardation-1 Gene (FMR1) FMR1 gene > produces Fragile X Mental
Retardation Protein (FMRP) FMRP > a widely expressed
mRNA-binding Translational Regulator with reportedly hundreds of
potential targets.
- 17. 1- DNA: Double stranded helix > Nucleotides >
Nucleobase 2- RNA: 3-Proteins:
- 18. FXS: FMR1 gene Medscape reference 2013 In FXS a full
mutation in the FMR1 gene > Hyper-methylation of FMR1 gene >
FMRP is not manufactured: (^Degree of methylation > ^degree of
severity of FXS). Most commonly 29 - 30 repeats Premutation Full
Mutation
- 19. FMRP: regulatory protein of messenger RNA (mRNA) in neurons
and dendrites Lack of FMRP > downgraded receptors in synapses.
> suppression of neuronal transmission > slow transmission in
the brain cells > poor brain development FXS: FMR1 gene Medscape
reference 2013
- 20. 55-199 repeats: PREMUTATION > enhanced production of
FMR1-mRNA (2 8 times normal levels). > Primary Ovarian
Insufficiency (40s-50s) > Fragile X-associated Tremor/Ataxia
Syndrome (FXTAS). (60s-70s) 200 repeats or more: FULL MUTATION >
Hyper methylation of the repeats in the FMR1 region > Reduced or
absent FMR1- mRNA > Decreased or absent Fragile X Mental
Retardation Protein (FMRP) > FXS. FXS: Mutations &
Premutation
- 21. FXS: Mode of Inheritance
- 22. FXS: Mode of Inheritance Medscape reference 2013 Females
with full mutation: Unaffected mildly affected (LD, autism or
physical features of FXS). (? X Inactivation) 50% boys: FXS 50%
girls: carriers with full mutation. Females with premutations:
20-25%: Primary Ovarian Insufficiency. 4-8%: FXTAS Increased risk
of autoimmune disorders (hypothyroidism & fibromyalgia). CGG
triplets are UNSTABLE > boys and girls > full mutation or
premutations.
- 23. Males with a full mutation: Individuals: have full FXS.
Sons: are unaffected > only get Y chromosome Daughters:
mutations or premutation to one X chromosome (sperm: MOSAICS). Most
closely resembles X- linked dominance with partial penetrance (see
Dobyns et al 2004). FXS: Mode of Inheritance Medscape reference
2013
- 24. Males with premutations: Individuals: Unaffected Mild FXS
(LD, autism or physical features of FXS). 40%: FXTAS in old age.
Daughters: exact premutation (no MOSAICS). FXPOI, FXTAS +/- mild
FXS. Sons: unaffected (only get Y chromosome). FXS: Mode of
Inheritance Medscape reference 2013
- 25. - Most patients (98%) with FXS > CGG triplet expansion -
Few patients (2%) > other abnormalities e.g. POINT MUTATION or
DELETION of the FMR1 gene. FXS: Mode of Inheritance Medscape
reference 2013
- 26. FXS: Mosaic Patterns Mosaic patterns > common in males
> unstable number of repeats over generations > pattern of
inheritance difficult to predict. (Allele) Size mosaic: different
sizes of the repeat expansion in different cells. Most common form
of mosaic males. Sperm mosaic: different sperms have different
sizes of the repeat expansions. Methylation mosaic: Incomplete
methylation of a full mutation.
- 27. X Inactivation / Dosage Compensation
- 28. FX- Associated syndromes
- 29. Fragile X-associated tremor ataxia syndrome (FXTAS): 33-46%
of men, with permutations, older than 50 years. 4-8% in older women
with permutations . Other signs of neurodegeneration: Brain
atrophy, Middle cerebellar peduncle lesions. Intranuclear
inclusions Peripheral neuropathy, Autonomic dysfunction Clinical
features of FXTAS include: Cerebellar ataxia, Dementia, Anxiety,
Irritability, Depression, Incontinence, Impotence,
- 30. Fragile X-associated Primary Ovarian Insufficiency :
Reported in 20-25% of women with permutations; 30-fold increase
compared with the general population. Women with a diagnosis of
ovarian insufficiency: 2-15% have a permutation of FXS. Directly
related to the number of CGG repeats: Premature ovarian failure
Early menopause Irregular menses, Decreased fertility, Elevated
FSH
- 31. FXS: Genetic Tests
- 32. Cytogenetic Testing: Conventional cytogenetic testing or
(chromosome analysis), (karyotyping): Molecular Cytogenetics
Testing via Fluorescence in-Situ Hybridization (FISH) Microarray
Comparative Genomic Hybridization (aCGH) Testing DNA/Genetic Tests:
florescent/ radioactive probes Polymerase chain reaction (PCR): The
Rapid Polymerase Chain Reaction-Based Screening test Southern Blot
Analysis, Immunocytochemical testing: The methylation-specific
melting curve analysis (MS-MCA): Willemsen Antibody Test. Genetic
Tests Medscape reference 2013
- 33. Genetic Tests Specific Chromosome Disorder: karyotyping /
Chromosome analysis. Specific genetic disorder: Diagnosis: PCR or
Southern Blot Analysis. FISH: labels the gene on the chromosome.
Screening: Immunocytochemical testing e.g. Willemsen Antibody Test.
The Rapid PCR-Based Screening test No specific genetic disorder:
Microarray Comparative Genomic Hybridization (aCGH) Testing.
- 34. FXS: Screening Tests Sabaratnam & Thakker, 2003;
Medscape reference 2013 Polymerase Chain Reaction (PCR): Is the
routine screening test used on FXS. Faster, less expensive &
requires a minimal sample, Effective for small premutations but not
very sensitive in full mutations. The Rapid PCR-Based Screening
test (Blood Spot Test ) (Tassone et al, 2008): Both males and
females 55 to 200 CGG repeats & full-mutation ranges. Rapid
detection using even 1% of the DNA from a single dried blood spot.
Screening large populations. Costs $5 : $1 per sample. Flora
Tassone
- 35. ASURAGEN Amplide FMR1 PCR
- 36. FXS: Drug Treatment
- 37. FXS: Drug Treatment
- 38. FXS: Drug Treatment
- 39. 39
- 40. 40
- 41. Plasticity: Long-Term Potentiation (LTP) & Long-Term
Depression (LTD)
- 42. In the normal state: mGluR activation by glutamate (glu)
results in activation of dendritic translation through the
phospholipase C (PL-C) cascade. FMRP levels increase with
translational activation, and FMRP then inhibits translation,
acting as the negative feedback or brake on the translational
mechanism.
- 43. When FMRP is missing in FXS: mGluR-mediated translation
lacks the negative feedback balance > excessive: Synthesis of
specific synaptic proteins, Internalization of AMPA receptors,
Other synaptic changes > Excessive long-term depression. >
persistently weak and immature synapses.
- 44. MPEP & other mGluR5 ve modulator > blocks
mGluR-mediated LTD Lithium: blocks inositol phosphate (IP)
turnover, and blocking PL-C mediated signal transduction, also
inhibits GSK3 activity > block in part excessively activated
mGluR-mediated translation. CX516 or other Ampakines: increases
AMPA activity directly & redistributes AMPA receptors to the
synaptic membrane through activation of BDNF.
- 45. Fenobam mGluR5 antagonist Open-label, single-dose trial in
12 adults. AFQ056 mGluR5 antagonist Phase II trials in adults and
adolescents and Phase I trials in children underway Acamprosate
Probable mGluR5 antagonist, Open-label study in 3 adult males.
Phase III trial in children underway RO4917523 mGluR5 antagonist
Phase II trials in adult males underway STX107 mGluR5 antagonist
Phase II trials in adult males in development Riluzole believed to
block presynaptic glutamate release. Open-label study in 6 adult
males: Memantine NMDA antagonist Chart review of 6 young adults
treated Minocycline MMP-9 inhibitor Phase II trials in children
recently completed. Lithium GSK3 inhibitor; increases BDNF
production Open-label study in 15 children and adults: Arbaclofen
GABABR agonist Phase II randomized, placebo-controlled trial in 63
children and adults: Phase III trials in children and adults
underway CX516 Positive modulation of AMPA receptors Randomized,
placebo-controlled trials in 49 adults: OT Neuropeptide involved in
pro- social behaviour Randomized, placebo-controlled trial in 10
young adult males: Donepezil Acetylcholinesterase antagonist
Open-label trial in 9 adults. Randomized controlled trial in young
adults underway
- 46. In mice (& other animals) with FXS, data supporting the
mGluR theory and drugs that correct mGluR overexpression are
robust, with many studies reporting phenotypic rescue' and
behaviour that is indiscernible from WT). Drug Trials: Conclusion
Politte et al, 2013
- 47. In human trials: Not the same Results of targeted treatment
trials have been encouraging but not striking. Treatment improves
behaviours; do not reverse physical phenotype. Trials >
increased methodological difficulties > significant potential
for bias In animals: Both reduced and enhanced NMDAR functioning
> ASD in mice. Why: Biological differences. More complex model:
FXS > diverse symptoms, LD, ASD, ADHD (??). FXS Drug Trials:
Conclusion Politte et al, 2013
- 48. Most favourable outcomes would be obtained with early
childhood intervention, The choice of target population in future
clinical trials should be carefully considered. Number of CGG
repeats Extent of methylation Associated pathology Stage of
development Still many other potential therapies are to be
discovered Drug Trials: Conclusion Politte et al, 2013
- 49. FXS: Management
- 50. Critical Period
- 51. Screening for FXS: Many FXS > late diagnoses >
missing the critical period. 50% of parents > another child or
pregnancy before diagnosis. Testing for FXS is recommended for FXS
families and high risk groups: Features of FXS and LD. LD. Autism.
Women with primary ovarian insufficiency. Aging adults with ataxia
or tremor combined with other features of FXTAS. Family history
consistent with FXS.
- 52. New-born screening for FXS > currently researched in
USA. Less-expensive screening methods have been developed >
Blood Spot Test (Tassone et al, 2008): less than $5 / test >
full mutation & premutation. If positive > further tests
e.g. PCR or Southern Blotting. Screening for FXS:
- 53. Risk for FXS > testing of the individual then family.
Referral to a geneticist and/or genetic counselling: Identify
individuals at risk Help with how information is conveyed to family
members. review reproductive options for future pregnancies,
including egg donation, prenatal diagnosis, adoption, and
pre-implantation genetic diagnosis through polar body analysis.
Help to be connected to support groups. Genetic Counselling
(Hagerman et al, 2009)
- 54. Educational Services (Hagerman et al, 2009) Research >
educational services, have been associated with better behavioural
outcomes and fewer autistic behaviours. Hagerman: I can make an FXS
child able to learn but I can not teach him. MIND institute >
New video games style educational programmes. Learning skills >
information.
- 55. Current research > IQ, symptoms and functioning of FXS
patients improve with positive elements in: Environment. Stress
management interventions. Sensory processing interventions.
Behavioural intervention teams / programmes. Psychotherapy or
Counselling. Speech therapy. Cognitive behavioural Therapy. Social
Skills-Oriented Group Therapy. REHABILITATIVE INTERVENTIONS
(Hagerman et al, 2009)
- 56. The Wheeler Family: TIME magazine: 2008 COMMENTS