Molecular analysis of fragile X syndrome

Curr Protoc Hum Genet. 2014 Jan 21:80:9.5.1-9.5.19. doi: 10.1002/0471142905.hg0905s80.

Abstract

The gene responsible for Fragile X syndrome, fragile X mental retardation-1 (FMR1), contains an unstable sequence of CGG trinucleotide repeats in its promoter region. Expansions of >200 trinucleotide repeats are considered full mutations and typically lead to abnormal methylation of the region, resulting in loss of FMR1 expression. Males with loss of FMR1 protein are expected to be affected by Fragile X syndrome, while females may or may not clinically manifest features of the condition. The protocols in this unit outline the complementary use of polymerase chain reaction (PCR) and methylation-sensitive Southern blot hybridization to accurately measure trinucleotide repeat size and methylation status. These protocols are also used to evaluate CGG repeat size in two adult-onset conditions known for their association with FMR1 premutation alleles, Fragile X Tremor/Ataxia (FXTAS) syndrome and Premature Ovarian Failure (POF).

Keywords: Fragile X; clinical; diagnostic; molecular; testing.

MeSH terms

  • Ataxia / diagnosis*
  • Ataxia / genetics*
  • Base Composition / genetics
  • Blotting, Southern
  • Female
  • Fragile X Mental Retardation Protein / genetics*
  • Fragile X Syndrome / diagnosis*
  • Fragile X Syndrome / genetics*
  • Gene Deletion
  • Genetic Predisposition to Disease
  • Genetic Testing / methods*
  • Humans
  • Male
  • Polymerase Chain Reaction / methods
  • Primary Ovarian Insufficiency / diagnosis
  • Promoter Regions, Genetic
  • Tremor / diagnosis*
  • Tremor / genetics*
  • Trinucleotide Repeat Expansion / genetics*

Substances

  • FMR1 protein, human
  • Fragile X Mental Retardation Protein

Supplementary concepts

  • Fragile X Tremor Ataxia Syndrome