Fever or fever-associated illness in children with autism is reported to result in temporary relief of cognitive and behavioral symptoms. It remains unknown, however, which aspects of this phenomenon — such as temperature increase, immune activation, type of pathogen or type of autism — are important for this benefit to occur.
The search for genetic risk factors for autism has revealed rare mutations in many genes. A critical step toward understanding autism is finding a common theme among the genes implicated in the disorder.
One of the core symptoms of autism is impaired interpretation of social cues and abnormal emotional responses to social cues. The amygdala is a brain region that plays a fundamental role in social functioning. Human imaging studies have demonstrated abnormal amygdala activity in people with autism, which is likely to contribute to the socio-emotional symptoms. However, the amygdala comprises several interconnected regions, and the neural basis for these behaviors is not clear.
The diverse genetic variations associated with autism are thought to affect molecular networks, which have yet to be identified. Dennis Vitkup and his colleagues at Columbia University in New York have developed an algorithm called NETBAG to search for clusters of genes perturbed by autism-associated genetic variations.
Deletion of the 16p11.2 chromosomal region is one of the most common causes of autism spectrum disorders (ASD) and developmental delay. Individuals with 16p11.2 deletion syndrome present with intellectual disability, language impairments, social deficits and motor delays. Interestingly, the magnitude of these deficits varies substantially from one individual to another. This makes the 16p11.2 deletion carrier population especially important for understanding the complex origins of the symptoms associated with ASD and other neurodevelopmental disorders.
In addition to problems in communication and social interaction, and the presence of restricted or repetitive behaviors, individuals with autism frequently exhibit altered sensory function. Sensory issues are commonly seen in more than one domain, and the ability to synthesize or integrate information across senses is often affected. There is little empirical information, however, that systematically characterizes the sensory and multisensory deficits in people with autism, or that relates sensory changes to cognitive abilities.
Shared exposure to environmental factors appears to have a more prominent role in autism than genetics does. Polybrominated diphenyl ethers (PBDEs) are members of an important group of chemicals used in plastics, textiles, furniture and electronic devices. The global production of PBDEs has reached approximately 148 million pounds per year. PBDEs are used as flame retardants in plastics, to which they do not bind chemically. They can thus leach from polymers and pervasively accumulate in the built environment and ecosystem.
One of the most important steps in postnatal brain development is the formation of the connections between neurons, known as synapses. These connections establish the neural circuits that control behavior. NMDA receptors are key molecules in the development and functioning of synapses that use the neurotransmitter glutamate.
Imprinted genes are an unusual class of genes that preferentially express either the maternally or paternally inherited gene copy in the child. A role for imprinted genes in autism-related behaviors has been established through studies of Angelman syndrome, a disorder characterized by features of autism and resulting from loss of the maternally expressed gene UBE3A[ref]Van Buggenhout G. and J.P. Fryns Eur. J. Hum. Genet. 17, 1367-1373 (2009) PubMed[/ref]. This gene is located in an imprinted gene cluster in the 15q11-13 chromosomal region.
Autism spectrum disorders represent a complex set of neurodevelopmental disorders that involve a combination of many different genes and environmental factors and affect multiple parts of the brain. The molecular and cellular mechanisms that lead to autism remain elusive.