How is brain structure and function different between deletion and duplication carriers? 

Previous studies have shown that 16p11.2 deletions and duplications are associated with autism, speech and language disorders, psychiatric conditions, epilepsy, and other features, suggesting that these genetic changes have effects on the brain structure and function. It has also been found that “mirror phenotypes” occur for some features (having the deletion versus the duplications affects individuals in opposite ways); for example, people with a 16p11.2 deletion tend to have a larger than typical size head (called macrocephaly) and have a higher body mass index (BMI) putting them at a higher risk of developing obesity, while people with a 16p11.2 duplication tend to have a smaller than typical head size (called microcephaly) and have a lower BMI. This information led to the questions of: how is brain structure different between individuals with the 16p11.2 deletion or duplication and does having the deletion versus the duplication cause opposite effects?

Brain structures of 16p11.2 deletion and duplication families from Simons VIP were analyzed and compared to those of children who do not carry either a 16p11.2 deletion or duplication. In children with the deletion, missing a copy of the 16p11.2 region causes the brain volume (size) to be larger, while in children with the duplication, having an extra copy of the 16p11.2 region causes the brain volume to be smaller. These differences in size (larger in deletion, smaller in duplication) were also seen across the different structures and areas of the brain. This means that the brain was uniformly larger/smaller, rather than one specific area of the brain being larger/smaller. This finding appeared to be stable across the lifetime, from childhood to adult, and suggests that 16p11.2 causes differences in brain volume early in development.  

Original article published August 2014

Read the Abstract (scientific summary) here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4138332/