Fragile-X Syndrome: one more step to finding a cure for this disease
Under normal condition (left), FMRP helps produce the Dgkk enzyme in neurons. In the fragile X situation, in the absence of FMRP (right), Dgkk is not sufficiently produced. Acting on Dgk enzymatic activity would be a way to correct the defects associated with the fragile X syndrome.
© IGBMC / Hervé Moine
Proc Natl Acad Sci U S A June 28, 2016
July 11, 2016
A study supervised by Hervé Moine evidenced a pathogenic mechanism for fragile X syndrome. This genetic disease most often causes intellectual disabilities, behavioral problems and physical abnormalities. These results were published in the Proceedings of the National Academy of Sciences (PNAS) on May 27th.
Fragile X-syndrome (FXS) affects one in 4000 men and one in 8000 women. FXS represents the first familial cause of intellectual disability and also the first known cause of autism spectrum disorder symptoms(1). FXS is caused by an abnormal expension of a DNA segment in the FMR1 gene on the X chromosome, leading to the loss of expression of the gene. FMR1 gene encodes a protein (FMRP) that is essential for communication mechanisms between neurons in several brain regions. The mechanism responsible for the symptoms of FXS, and more specifically the molecular cause leading to the alteration of neuronal function, is still poorly understood.
FMRP helps the manufacturing of Dgkk enzyme
Until now, researchers knew that the absence of FMRP caused an excess of synthesis of numerous proteins in neurons, this excess is considered as one of the main causes underlying the disease, however, they did not know how the absence of FMRP caused this phenomenon.
In a collaborative study funded by the "agence nationale de la recherche" (ANR), the fondation Jérôme Lejeune, and the Labex-INRT (ANR) the team of Jean-Louis Mandel, to which Hervé Moine belongs, showed that FMRP helps synthesize an enzyme called diacylglycerol kinase kappa (Dgkk). This enzyme is essential for the production of membrane lipids involved in the communication and strengthening of connections between neurons (synapses).
The researchers showed that this mechanism was disrupted in the absence of FMRP protein in a mouse model developing the disease. They also found these same disturbances in samples of FXS patients. These results open new perspectives for the discovery of a treatment for this disease.
(1) The autism spectrum disorders (ASDs) are neurological disorders that primarily affect social relationships and communication in children. These disorders are also manifested by the appearance of atypical (unusual) behavior and the development of narrow interest in young or adult who has it.