Fragile X syndrome and Autism Spectrum disorders
Fragile X syndrome is caused by genetic mutation which results in the absence or incorrect production of a protein called FMRP. Fragile X syndrome is the most common cause of inherited intellectual disability and is strongly associated with autism spectrum disorder characteristics.
Researchers in Belgium, Italy and Amsterdam have collaborated in order to investigate the role of FMRP in brain development. The researchers used mouse models of fragile X syndrome in which the production of FMRP had been switched off in the mice’s brains. They found that FMRP regulates the maturation and positioning of brain cells in the outer layer of the brain (the cortex) as mouse embryos are developing. The researchers were also able to unravel the molecular mechanism which allows FMRP to perform this regulation. Key to showing that FMRP is fundamentally important in this regulation, the researchers switched FMRP production back on in their mice and showed that the differences in the mice’s brains, which they had previously observed, returned to normal.
This collaborative study suggested that an important result of FMRP being absent during the development of the brain while babies are growing before birth, is that the cortex does not form properly. This suggests that after babies with Fragile X syndrome are born, the fine-tuning of brain connectivity (how different areas of the brain link up to one another so that they can pass important messages between them) which usually occurs very early in life does not happen in the same way as usual.
The brain cortex is where information from the rest of the body is received, processed and interpreted. This elaborate information is then converted into thoughts and driving signals for the body. Therefore, mistakes or delays in the correct development of the brain cortex, can lead to impaired ability to interpret and process the information we need in our daily lives. Impaired brain connectivity has been recognised as a key deficit in ASD and this study may explain why some people with fragile X syndrome have autism-related symptoms.