|
Fragile X syndrome (FXS) is the most common inherited form of mental retardation in males with an estimated frequency of 1/4000.
Symptoms include:
- moderate to severe mental retardation
- macroorchidism
- elongated face
- immature-appearing dendritic spines
- hyperactivity
- increased sensory sensitivity
- autistic behavior
- seizures
|  |
|
|
|
FXS is usually caused by the expansion of a CGG repeat sequence in the fragile X mental retardation gene (FMR1) on the X chromosome. Normally the CGG repeat sequence has 4-55 repeats. The fragile X premutation is characterized by a CGG repeat sequence of 55-200. In this range the repeat sequence is unstable and tends to expand in succeeding generations. When the sequence length expands to greater than 200 repeats, FMR1 |
| |
|
is silenced, and, as a consequence, its protein product, fragile X mental retardation protein (FMRP) is absent. This is known as FXS or the full mutation.
|
|
|
Fragile X premutation carriers are at risk for:
- fragile X associated tremor ataxia syndrome (FXTAS)
- premature ovarian insufficiency (POI) in female carriers
- attention deficit hyperactivity disorder (ADHD)
- autistic spectrum disorder (ASD)
- mild cognitive impairments
Questions addressed in our ongoing work:
- How does the lack of FMRP results in the symptoms of FXS?
- What is the function of FMRP in the normal brain?
|
|
|
