Some Shared Characteristics of Fragile X and Autism

Images of the frontal cortex stained for the FMRP protein. Courtesy: Jarek Wegiel

Fragile X syndrome (FXS), caused by lack of fragile X mental retardation protein (FMRP), is associated with a high prevalence of autism. In people with duplication of a portion of chromosome 15 (Dup15q), about 80% also have a diagnosis of autism, presumably due to the genetic differences on chromosome 15. It is not clear whether these individuals have any alterations of FMRP. This study tested the hypothesis that both idiopathic (no genes currently known) and syndromic (Dup15q) autism are associated with brain region-specific deficits of neuronal FMRP and structural changes of the affected neurons. Researchers at the Institute of Basic Research in NY carried out immunohistochemical staining of postmortem brain tissue and discovered that FMRP is missing in neurons in the cerebral cortex and that these neurons appear shrunken. Other brain cells appear to have too much FMRP. The authors suggest that dysregulation of FMRP may be a common feature of autism beyond Fragile X syndrome.

Wegiel J, Brown WT, La Fauci G, Adayev T, Kascsak R, Kascsak R, et al. (2018): The role of reduced expression of fragile X mental retardation protein in neurons and increased expression in astrocytes in idiopathic and syndromic autism (duplications 15q11.2-q13). Autism Res.