08:18pm Friday 15 December 2017

Fragile X gene determines late-onset dementia

In research published in the August edition of the journal Neurology, Monash researchers Professor Kim Cornish and Dr Darren Hocking led a team which examined impulsivity, attention and working memory skills of men aged 18 to 69 years, who were all carriers.

Men who are carriers of the FMR1 (Fragile X Mental Retardation 1) gene may be at high risk of developing severe dementia as they age, despite having no obvious symptoms earlier in life.

The FMR1 gene occurs in two stages: as a small-medium expansion (carriers) and as a large expansion. Those with the large expansion will have Fragile X Syndrome (FXS) and experience the full effects.

Approximately one in 250 women and one in 800 men will be carriers of the FMR1 gene. For many years, those who carried the gene were assumed to be unaffected by any of the challenges faced by those with FXS.

The men were tested for their ability to phase out irrelevant information as well as actively store short-term information. These core brain functions decline with late-stage dementia.

The research found that carriers of the gene who were at the upper end of the medium expansion were more likely to have problems with inhibition and remembering materials, demonstrating cognitive dementia symptoms, whereas those who had expansions just within the medium range appeared risk-free.

Their findings will make it easier to accurately identify men who may go on to develop Fragile X-associated dementia and influence current approaches to diagnosing, preventing and treating this disorder.

Professor Cornish, who conceptualised and designed the study, said that it provided the first clear evidence that being a male carrier with a larger expansion may infer some risk.

“Until 10 years ago, it was assumed that carriers of Fragile X syndrome would remain free of symptoms as they grew older,” Professor Cornish said.

“It is now well-documented that approximately 30 to 40 per cent of PM males will develop FXS-related late-stage dementia.

Recognising the need to identify risk factors in Australian carriers of the FXS gene, a new study funded by the Australian Research Council and led by Professor Cornish will for the first time, chart the history of strengths and challenges facing carriers across the lifespan.  

Professor Cornish’s research is featured on the Neurology website and will be included in their podcast series in August.  Her team is based in the School of Psychology and Psychiatry and also in the newly established Monash Institute for Brain Development and Repair (MIBDR).

July is Fragile X Awareness Month. To learn more about the world’s leading inherited cause of intellectual disability and further ground-breaking research into the condition, visit the Fragile X Association at www.fragilex.org.au.

For more information or to arrange an interview contact Ali Webb, Monash Media & Communications + 61 3 9903 4841 or ali.webb@monash.edu


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