Il est désormais établi que le trouble du spectre de l’autisme (TSA) est d’origine multifactorielle, c’est-à-dire qu’il se déclare chez des personnes génétiquement prédisposées après exposition à un ou plusieurs facteurs environnementaux.
Les facteurs environnementauxincriminés incluent notamment la prise de certains médicament pendant la grossesse, la prématurité ou le manque d’oxygène à la naissance. A ce jour en revanche, des preuves scientifiques solides excluent le rôle des vaccins dans l’apparition de l’autisme.
Les études épidémiologiques montrent un ratio de 3 garçons atteints pour 1 fille.
La composante génétique est aujourd’hui confirmée par la forte concordance de l’autisme chez les jumeaux monozygotes. On sait également que le risque d’avoir un enfant atteint de TSA est 50 à 100 fois plus élevé dans la fratrie d’une personne autiste.
Is autism genetic?
We now know of several hundred ASD predisposition genes, i.e. genetic variants that increase the risk of developing the disease in individuals who carry them. These variants are neither necessary nor sufficient to develop ASD, i.e. a person carrying a given variant may not have ASD and an autistic person may not carry this variant.
The predisposition genes identified are mainly involved in neurotransmission (the passage of information from one neuron to another), in the formation of synapses (where neurotransmission passes) and, more generally, in brain development.
At the Paris Brain Institute: Clinical researchers from the Institut du Cerveau and the Centre du Neurodéveloppement Adulte (CNA, a unit of the Adult Psychiatry Department at the Hôpital Pitié Salpêtrière) are setting up a study into the neuroanatomical and functional markers of the autism spectrum in adult women. The aim is to compare MRI data from young women with autistic features but no diagnosis of ASD with data from women with autism and women without autistic features.
Certain brain abnormalities have been identified in people with autism and are located in the ventricles (dilatation), in the cerebellar vermis, in the brain stem nuclei and in the hippocampus.
The CHD8 gene is one of the predisposition genes for autism, conferring a high risk of developing the disease. In 2018, Carlos PARRAS, an Inserm researcher in the team led by Bassem HASSAN, highlighted the role of the protein encoded by this gene in the differentiation of oligodendrocytes. These central nervous system cells have two essential roles:
- Myelination, i.e. the formation of an insulating and protective sheath for neurons, myelin, which facilitates the passage of nerve messages.
- The supply of energy to neurons, to ensure optimal functioning of these cells.
A, A1, B, B1: Expression of the Chd8 protein (marked in red) in maturing or mature oligodendrocytes (white arrows) and in neurons (grey arrows). C: Spectrum of Chd8 protein expression during oligodendrocyte maturation.
The results of this research show an important role for oligodendrocytes in the cerebral abnormalities at the root of autism spectrum disorders.
AT THE PARIS BRAIN INSTITUTE
Clinical researchers from the Institut du Cerveau and the Centre du Neurodéveloppement Adulte (CNA, a unit of the Adult Psychiatry Department at the Hôpital Pitié Salpêtrière) are setting up a study looking at neuroanatomical and functional markers of the autism spectrum in adult women.
The aim is to compare MRI data from young women with autistic features but no diagnosis of ASD with data from women with autism and women without autistic features.