Genetics: Tuberous sclerosis, fragile X share immune changes
Two autism-related disorders — fragile X syndrome and tuberous sclerosis complex — share disruptions in the immune system despite major differences in the individual genes affected, reports a study published 24 February in Molecular Autism1.
An abnormally regulated immune system is linked to some forms of autism, but exactly how genetic changes in the immune system contribute to autism is unclear.
Fragile X syndrome and tuberous sclerosis complex (TSC) both have disruptions in a pathway that regulates protein levels at the synapse — the connection between neurons. Fragile X is caused by mutations in the FMR1 gene, whereas mutations in the TSC1 or TSC2 genes are responsible for tuberous sclerosis. Both are often accompanied by autism.
In the new study, researchers compared gene expression in the blood and brain tissues of two different mouse models. Mice with an inactive FMR1 gene provide a model for fragile X syndrome and the TSC mouse model carries an inactivated copy of TSC2.
The researchers expected to find similar expression profiles in both mice strains. They instead discovered that the disorders have distinct gene expression patterns, but share some affected pathways.
Both strains show changes in three immune-related pathways: a cytokine signaling pathway that regulates the inflammatory response, a cell communication pathway and one involved in the development of blood cells, including important immune cells.
The new study supports the prediction that drug therapies will need to be tailored for specific forms of autism. However, those targets may converge on commonly affected biological pathways, the researchers suggest.
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1. Kong S.W. et al. Mol. Autism. 5, 16 (2014) PubMed