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Updated: Oct 9, 2026

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene
08:22

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene

Published on: September 16, 2019

The FMR2 gene, FRAXE and non-specific X-linked mental retardation: clinical and molecular aspects

J Gecz1

  • 1Department of Cytogenetics and Molecular Genetics, Centre for Medical Genetics, Women's and Children's Hospital, North Adelaide, SA, Australia. jgecz@mad.adelaide.edu.au

Annals of Human Genetics
|March 14, 2001
PubMed

Insights

FRAXE fragile site mental retardation, the most common X-linked form, is linked to the FMR2 gene. Repeat expansions in FRAXE silence FMR2, causing mild to borderline intellectual disability.

Area of Science:

  • Genetics
  • Neuroscience
  • Molecular Biology

Background:

  • FRAXE fragile site mental retardation is a prevalent X-linked condition with mild to borderline intellectual disability (IQ 50-85).
  • It is the most common form of non-specific X-linked mental retardation, affecting at least 1 in 50,000-100,000 males globally.
  • The FRAXE site is located near the FMR2 gene, and repeat expansions are known to silence its transcription.

Purpose of the Study:

  • To review current data on FRAXE-associated mental retardation and the FMR2 gene.
  • To contextualize these findings within recent discoveries of genes responsible for other non-specific X-linked mental retardation forms.
  • To explore the molecular mechanisms underlying FRAXE fragile site mental retardation.

Main Methods:

  • Literature review of genetic and molecular studies on FRAXE and FMR2.
  • Analysis of existing data on the prevalence and genetic basis of X-linked mental retardation.
  • Comparison of FMR2 gene characteristics with newly identified genes for non-specific X-linked mental retardation.

Main Results:

  • Hyperexpansion of the FRAXE CCG repeat leads to FMR2 gene transcriptional silencing.
  • The FMR2 gene's structure is known, but its function remains elusive.
  • Recent advances have identified genes involved in common signaling pathways for other forms of non-specific X-linked mental retardation.

Conclusions:

  • FRAXE-associated mental retardation is primarily caused by FMR2 gene silencing due to CCG repeat expansions.
  • Understanding FMR2's function is crucial for elucidating the pathophysiology of FRAXE mental retardation.
  • Continued research into X-linked mental retardation genes may reveal shared molecular pathways.

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