Prenatal and early childhood infections have been implicated in autism.
Many autism susceptibility genes (206 Autworks genes) are localised in
the immune system and are related to immune/infection pathways. They are
enriched in the host/pathogen interactomes of 18 separate microbes
(bacteria/viruses and fungi) and to the genes regulated by bacterial
toxins, mycotoxins and Toll-like receptor ligands. This enrichment was
also observed for misregulated genes from a microarray study of
leukocytes from autistic toddlers. The upregulated genes from this
leukocyte study also matched the expression profiles in response to
numerous infectious agents from the Broad Institute molecular signatures
database. They also matched genes related to sudden infant death
syndrome and autism comorbid conditions (autoimmune disease, systemic
lupus erythematosus, diabetes, epilepsy and cardiomyopathy) as well as
to estrogen and thyrotropin responses and to those upregulated by
different types of stressors including oxidative stress, hypoxia,
endoplasmic reticulum stress, ultraviolet radiation or
2,4-dinitrofluorobenzene, a hapten used to develop allergic skin
reactions in animal models. The oxidative/integrated stress response is
also upregulated in the autism brain and may contribute to myelination
problems. There was also a marked similarity between the expression
signatures of autism and Alzheimer's disease, and 44 shared
autism/Alzheimer's disease genes are almost exclusively expressed in the
blood-brain barrier. However, in contrast to Alzheimer's disease,
levels of the antimicrobial peptide beta-amyloid are decreased and the
levels of the neurotrophic/myelinotrophic soluble APP alpha are
increased in autism, together with an increased activity of α-secretase.
sAPPα induces an increase in glutamatergic and a decrease in GABA-ergic
synapses creating and excitatory/inhibitory imbalance that has also
been observed in autism. A literature survey showed that multiple autism
genes converge on APP processing and that many are able to increase
sAPPalpha at the expense of beta-amyloid production. A genetically
programmed tilt of this axis towards an overproduction of
neurotrophic/gliotrophic sAPPalpha and underproduction of antimicrobial
beta-amyloid may explain the brain overgrowth and myelination
dysfunction, as well as the involvement of pathogens in autism.
Many autism susceptibility genes (206 Autworks genes) are localised in
the immune system and are related to immune/infection pathways. They are
enriched in the host/pathogen interactomes of 18 separate microbes
(bacteria/viruses and fungi) and to the genes regulated by bacterial
toxins, mycotoxins and Toll-like receptor ligands. This enrichment was
also observed for misregulated genes from a microarray study of
leukocytes from autistic toddlers. The upregulated genes from this
leukocyte study also matched the expression profiles in response to
numerous infectious agents from the Broad Institute molecular signatures
database. They also matched genes related to sudden infant death
syndrome and autism comorbid conditions (autoimmune disease, systemic
lupus erythematosus, diabetes, epilepsy and cardiomyopathy) as well as
to estrogen and thyrotropin responses and to those upregulated by
different types of stressors including oxidative stress, hypoxia,
endoplasmic reticulum stress, ultraviolet radiation or
2,4-dinitrofluorobenzene, a hapten used to develop allergic skin
reactions in animal models. The oxidative/integrated stress response is
also upregulated in the autism brain and may contribute to myelination
problems. There was also a marked similarity between the expression
signatures of autism and Alzheimer's disease, and 44 shared
autism/Alzheimer's disease genes are almost exclusively expressed in the
blood-brain barrier. However, in contrast to Alzheimer's disease,
levels of the antimicrobial peptide beta-amyloid are decreased and the
levels of the neurotrophic/myelinotrophic soluble APP alpha are
increased in autism, together with an increased activity of α-secretase.
sAPPα induces an increase in glutamatergic and a decrease in GABA-ergic
synapses creating and excitatory/inhibitory imbalance that has also
been observed in autism. A literature survey showed that multiple autism
genes converge on APP processing and that many are able to increase
sAPPalpha at the expense of beta-amyloid production. A genetically
programmed tilt of this axis towards an overproduction of
neurotrophic/gliotrophic sAPPalpha and underproduction of antimicrobial
beta-amyloid may explain the brain overgrowth and myelination
dysfunction, as well as the involvement of pathogens in autism.
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