Saturday, August 4, 2012

Genetic factors contributing to autism

Genetics is a complicated field. Applying that to a complicated developmental disorder such as ASD, can be overwhelming for most people. In this post, I will try to explain some of the theories about how genetics is contributing to ASD. This is based on the recent publication by Berg and Geschwind in Genome Biology (here). Importantly, however, this approach does not consider the contribution of environmental effects, for which there is sufficient evidence in ASD and other diseases.
To begin with, our DNA is individual, but not so different that it can't be traced to our parents and grandparents. DNA changes that occur during conception of an individual are called variants. When you look across the DNA of hundreds and thousands of people there are common variants (shared by at least 5% of people) and rare variants. These variants may cause disease, or have no effect. Studies investigating the DNA of thousands of people, including hundreds of individuals with ASD have been undertaken. Given that ASD is relatively common (~1%) it could be expected that common variants are responsible for ASD. However, the results reveal that, apart from a handfull of common variants, ASD is not associated with common variants. Given that ASD remains unexplained by common variants, researchers thought that maybe rare variants might explain the remainder of ASD cases. But, like common variants, rare variants were insufficient to explain most cases of ASD. Rare variants including whole deletions of DNA or duplications of DNA do increase the risk of ASD, but not guarantee it.
But what if there was a combination of common and rare variants, that when coming together in the same person, caused ASD. And it is more or less this point of understanding that ASD researchers have reached. To add another layer of complexity to this, rare DNA variants can have a large, medium or small effect on an individual. The size of this effect depends on the function of the DNA where the variant is occurring. 
To summarise the genetic possibilities that can account for ASD, I have listed them below (paraphrased from the Genome Biology article).
1. A few common variants may mean you develop ASD-like traits. Many common variants means you develop ASD.
2. A few common variants plus one medium-large rare variant may mean you develop ASD-like traits. But, many common variants plus one medium-large rare variant means you develop ASD.
3. A few common variants plus one medium-large rare variant may mean you develop ASD-like traits. But, many common variants plus one medium-large rare variant and/or many small rare variants means you develop ASD.
4. One small rare variant may mean you develop ASD-like traits. But many small rare variants means you develop ASD.
5. One large rare variant means you develop ASD.
From the evidence, it appears that theories 2-4 are likely, but not 1 or 5.
Theories 2-4 help explain why one child might have ASD, but the brother or sister does not. They also help explain why a child with a variant has ASD, but the parent with the same variant does not have ASD (they will have additional variants that effect the individual differently).
This synopsis of genetics portrays variants as disease causing, or predisposing to disease. But some variants may inadvertantly act in a healthy way by counter-acting disease causing variants. This of course means that the possbilities above are slightly simplistic.
Based on the information above, it is also important to understand that current DNA testing available to the public is unlikely to explain why an individual has ASD. It will only reveal if there is a large rare variant. And from the information above, we know that a large rare variant alone may only be a part of the cause.

Friday, August 3, 2012

BioAutism 2013


Sunday, 3rd February

An official 2013 ANS satellite meeting, BioAutism 2013 will focus on the neural and biological basis of autism spectrum disorders (ASD). It is estimated that 1 in 100 children are diagnosed with an autism spectrum disorder each year. While the causes of autism are not clear, in recent years significant progress has been made towards unraveling the underlying disease etiology and candidate mechanisms. The aim of this meeting is to bring together researchers working on autism spectrum disorders from multiple disciplines, with the specific goal to consider how basic and clinical research can accelerate therapies and treatments.
Topics to be discussed include genetics, synaptic and circuit level mechanisms, cognitive mechanisms, animal models, moving from models and mechanisms to therapeutics.

The organisers include: Dr Elisa Hill (Uni Melb), A.Prof Tony Hannan (Florey/Uni Melb), Dr Naomi Bishop (La Trobe), Dr Randal Moldrich (UQ) and Dennis Crowley.

Current invited speakers include:

  • Prof Valsamma Eapen (UNSW): ASD in the clinic: Overlap and boundaries with other neurodevelopmental disorders 
  • Dr Kent Williams (Nationwide Children’s Hospital, OH, USA): Gastrointestinal disorders in autism
  • Prof Chris Pantelis (Uni Melb): Identifying risk and resilience genetic biomarkers to predict the risk for Autism Spectrum Disorder
A full program will be available closer to the day of the event.

Download our Flyer

    Thanks to the generosity of our principal sponsors, University of Melbourne and Florey Neurosciences Institute, there will be no fee for registration.
  • To register please email
  • Your full name and title 
    Your affiliation and address
    Email and telephone contact details 
    and whether your have any special dietary requirements.
  • Registrations will be accepted up until the close of business, Friday January 18 2013.

  • Despite being a scientific meeting, the organising committee is keen to have distinguished and interested members of the community attend. To register your interest, please email the local organiser Dr Hill (
  • Poster presentations are welcomed from registrants. Maximum poster size will be 1m wide x 1.4m long.

  • Ongoing and recruiting studies, and registered trials, are welcomed.

  • Abstract acceptance will be based on scientific quality.

  • Oral presentations will be offered to some selected and accepted abstracts.

  • Abstracts should be submitted to  Please indicate if you wish to be considered for an oral presentation.

  • The abstract submission deadline is the close of business, Friday 14 December 2012

  • The meeting will take place in the auditorium of Melbourne Brain Centre, Kenneth Meyer Building, Cnr Genetics Lane and Royal Parade, Parkville. 

  • Getting there and away: Nearest train station = Melbourne Central. Nearest tram stop = University of Melbourne/Royal Parade (Tram #19)
  • Parking is free in Royal Parade on Sundays and $7 flat rate all day under the Kenneth Myer Building
Accommodation adjacent to the University of Melbourne is available by contacting the colleges directly.

Transport to the Sunday ANS symposium or airport
Transport from the Melbourne Brain Centre to the Melbourne Convention Centre for the ANS symposium will be organised for departure immediately after BioAutism 2013. A series of maxi-cabs will be ordered. Parties will need to share the cab fare amongst themselves. So that we order the correct number of maxi-cabs, please notify a BioAutism committee member at the time of collecting your BioAutism name badge and program. Alternatively, if you need to go to the airport after BioAutism, please let us know.

Thank you to our:
Gold Sponsors: 
ICT For Life Sciences Forum  

Silver sponsors:

    Florey Institute of Neuroscience and Mental Health
    Millenium Science                     
    Giant Steps        

Bronze sponsors:

Bio21 Cluster:
Science Advantage:

Registration, presentation enquiries to Dr Elisa Hill