Fragile X

Fragile site/break just above the tip of the long arm of the X chromosome
FMR1 gene codes for Fragile X Mental Retardation Protein (FMRP)
If there is an expansion >200 repeats, methylation occurs which causes the DNA around the gene to become heterochromatin, inhibiting translation
Lack of FMRP leads to excessive production of dendritic proteins
Thus, dysregulation of glutaminergic signalling
This leads to reduced neuronal plasticity - consequences are learning and memory deficits & social problems, including social anxiety

Expansion

Normally CGG repeats can expand through male and female transmission
BUT when near the threshold - ie. when individual has a premutation expansion only occurs during female transmission
Normally, every 100 CGG repeats, there is an AGG repeat which helps anchor the DNA
Expansion can disrupt this anchoring

Fragile X Associated Tremor (FTAX)
Caused by abnormal mRNA gain of function

	Creado por Ellie Quinn hace más de 10 años

Apunte sobre Trinucleotide Repeat Expansion Disorders, creado por Ellie Quinn el 13/02/2014.