In search of autism’s roots

Symbol of neurodiversity – PLoS Biology

There’s an interesting editorial on autism in PLoS Biology, written by PLoS staffer Liza Gross. She looks at several papers on the possible origins of autism that have come out since the disastrous effect on vaccination caused by the irresponsible publication of Andrew Wakefield’s throughly discredited research that implicated the measles virus in the triple vaccine, with autism.

Probably the most important paper comes from Svante Paabo and Philipp Khaitovich at the Max Planck Institute for Evolutionary Anthropology in Leipzig, together with a world-wide bunch of co-authors. Their paper is titled “Disruption of an Evolutionarily Novel Synaptic Expression Pattern in Autism”. Their study, they say, draws a connection between the genetic risk architecture of autism and molecular features of cerebral cortex development unique to humans.

By analysing gene expression in the prefrontal cortex of 63 autism patients and control individuals, as well as 62 chimpanzees and macaques, from natal to adult age, they discovered the most profound relationships between gene variants involved in synaptic developments and connectivity, and autism that were unique to humans. As they put it: “Autism spectrum disorder (ASD) involves disruptions in cognitive functions related to socialization and communication, which are also among the key behavioral capacities that separate humans from other species. This suggests that ASD may involve alterations in evolutionarily novel, human-specific developmental processes. To test this, we measured developmental gene expression trajectories in the cerebral cortex of autism cases, matched controls, and non-human primates: chimpanzees and macaques. Among a large number of disrupted developmental patterns that we detected in autism, only one, mainly including synaptic genes, was enriched in autism-linked mutations. This suggests that changes in expression of these genes in ASD brains may play a causal role in disease etiology. The same gene set exhibited more developmental expression changes unique to the human brain than any other developmental pattern disrupted in autism, reflecting extension of the synaptic maturation period in humans. Taken together, we show that a recently evolved developmental expression pattern of synaptic genes altered in autism might be associated with intense social learning abilities unique to humans.”