Fragile XS yndrome by noM8ZI4

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									Fragile X Syndrome
   (Martin-Bell Syndrome)

      Amber Boone
 page6.htm
 Mild to Moderate
  Mental Retardation
 Long, narrow face
 Large, protuberant
 Macroorchidism
  (enlarged testicles)
 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
 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
  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
  – 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
 FMR1 expression was turned
  on early in embroyonic
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
 Study on in vitro
   – 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
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    magnocellularis and hippocampus are the major sites of FMR-1 expression in the human fetal brain. Nature Genetics,
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