Fragile XS yndrome by noM8ZI4

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									Fragile X Syndrome
   (Martin-Bell Syndrome)

      Amber Boone
 www.fragilex.org.uk/ page6.htm
               Characteristics
 Mild to Moderate
  Mental Retardation
 Long, narrow face
 Large, protuberant
  ears
 Macroorchidism
  (enlarged testicles)
               Background
 X-linked disease
 Mutation is located at Xq27.3
 FMR1 Gene
  – Polymorphic (CCG)n repeat in the 5’
    untranslated reagion of exon 1
  – Hypermethylation of a CpG island upstream of
    the mutation
    Finding the Causitive Gene
 Cloned the X Chromosome from a normal
  human into YACs
 Digested with EcoRI
  – Found a 5 Kb region that was unstable in
    pedigrees with Fragile X (pfxa1)
 Digested with PSTI
  – Narrowed the instability down to a 1 Kb region
    (pfxa2)
 Sequenced this region
Pfxa2 sequence
  Finding the Causitive Gene (cont)

 Used several RE to cut normal and Fragile
  X DNA isolated from human lymphnodes
  – Normal fragile X site varied from 45-95 bp
  – Infected individuals fragile X site was almost
    900 bp longer
 Finding the Causitive Gene (Cont)
 Physical map across
  the Fragile X region
  – Mostly done through
    Resriction Enzyme
    cleavage
  Finding the Causitive Gene (cont)
 Isolated a YAC in somatic cell hyprids containing
  part of the Fragile X site
 Bought a YAC library and used their clone as a
  probe
  – Obtained a YAC with the whole region
 Created a cosmid library from the YAC clone
 Cosmid subclones used to screen a cDNA library
  of human fetal brain RNA
  – The cosmids hybridized to a portion of a gene
    designated as FMR1
Pedigree of a family with the Fragile
      X mutation segregating
             FMR1 Expression
 Northern Blot of FMR1 was
  done on Human Tissue
  – Expressed in highest levels in
    the Brain and Testes
  – Slightly lower level in the
    Placenta, Lungs, Liver, and
    Kidneys
 FMR1 expression was turned
  on early in embroyonic
  development
Mouse Knockout
            More Findings
 Fragile X phenotype is caused from lack of
  FMRP expression
 FMRP was expressed in some men with full
  mutation, but no methylation
 Found alternatively spiced FMRP proteins in
  different locations in the body
                        Treatment
 Study on in vitro
  reactivation
   – Rare cases of individuals
     with the full mutation and
     unmethylation have shown
     that the problem is in the
     methylation, which inhibits
     the translation
   – 5-azadeoxycytidine to
     induce DNA demethylation
     in vitro
                                      Bibliography
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    magnocellularis and hippocampus are the major sites of FMR-1 expression in the human fetal brain. Nature Genetics,
    4: 147-152.
   Annemieke, J.M. et. al. (1991) Identification of a Gene (FMR1) containing a CGG Repeat coincident with a Breakpoint
    cluster Region Exhibiting Length. Cell, 65: 905-914.
   Bell, M. V., et al. (1991) Physical Mapping across the Fragile X: Hypermethylation andn Clinical Expression of the
    Fragile X Syndrome. Cell, 84: 861-866.
   Chiurazzi, P., et al., (1998) In vitro reactivation of the FMR1 gene involved in fragile X syndrome. Human Molecular
    Genetics, 7: 109-113.
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    Cell, 78: 23-33.
   Froster-Iskenius, U., et al., (1984) Transmission of the marker X syndrome trait by unaffected males: Conclusions from
    studies of large families. Human Genetics, 67: 419-427.
   Hinds, H. L., et al., (1993) Tissue specific expression of FMR-1 provides evidence for a functional role in fragile X
    syndrome. Nature Genetics, 3: 36-44.
   Jin, Peng, et al., (2004) Biochemical and genetic interaction between the fragile X mental retardation protein and the
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   Kirchgessner, C. U., et al., (1995) X inactivation of the FMR1 fragile X mental retardation gene. Journal of Medical
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   Kremer, E. J., et al., (1991) Mapping of DNA Instability at the Fragile X to a Trinucleotide Repeat Sequence p(CCG)n.
    Science, 252: 1711-1714.
   Mazroui, R., et al., (2002) Trapping of messenger RNA by Fragile X Mental Retardation protein into cytoplasmic
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   Ostra B. A., et al., (2001) The Fragile X gene and its function. Clinical Genetics, 60: 399-408.
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   Verheij, C., et al., (1995) Characterization of FMR1 proteins isolated from different tissues. Human Molecular Genetics,
    4: 895-901.

								
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