[LINK] "New Gene Studies Suggest There Are Hundreds of Kinds of Autism"

[rfmcdonald]

Wired shared Sarah DeWeerdt's fascinating article which uses the latest researches in genetics to argue that "autism" is not a single condition but rather a vast and diverse clade of superficially similar genetic conditions. This understood diversity has obvious implications for treatment.

Rather than recruiting people with autism based on outward characteristics, some researchers are turning this flood of genetic information into an advantage: They are classifying children with autism based on their genetics, and thoroughly characterizing each subgroup to map autism’s landscape as a whole. These ‘genetics-first’ studies, including the one in which Waylon and Geoffrey participate, may help researchers to construct a meaningful taxonomy of autism and understand the source of its diversity. Eventually, such studies may even lead to treatments that address the root cause of a child’s autism, rather than just the symptoms.

Researchers have known for a couple of decades from genetic disorders closely related to autism, such as Rett syndrome and fragile X syndrome, that people with a disruption in the same gene often have similar symptoms. In the past ten years or so, advances in technologies for sequencing and analyzing DNA have provided hints that the same is often true for people with so-called idiopathic autism, or autism of unknown cause.

Beginning in the mid-2000s, microarray technology revealed that people with autism tend to carry many copy number variations, deletions or duplications of large stretches of DNA that encompass multiple genes. Researchers soon saw that people who harbor the same copy number variants often share other characteristics and symptoms as well.

To investigate these commonalities, some teams began to look into subgroups of people with a common chromosomal alteration. The most comprehensive of these projects so far is the Simons Variation in Individuals Project (Simons VIP), which is characterizing about 200 people with variations of a chromosomal region called 16p11.2. (The Simons VIP is funded by the Simons Foundation, SFARI.org’s parent organization.) About 20 percent of individuals with deletions in this region and 10 percent with duplications have autism.

In the past couple of years, it has become feasible to look more closely at the DNA of people with autism by analyzing all of the protein-coding sequences in their genomes — about 1 percent of the roughly 3 billion base pairs that make up each genome. This approach has revealed that many people with autism have mutations that aren’t found in people without the disorder, but few people with autism share the same mutation. Despite analyzing genetic material from more than 2,500 people with autism, “We almost never saw the same gene hit twice,” says Evan Eichler, professor of genome sciences at the University of Washington and a leader of one of the first of these studies.