16p11.2 rearrangements: Genetic paradigms for neurodevelopmental disorders

Human genomes differ from one another in many respects. Some people harbor more or fewer than the typical number (two copies, one from each parent) of certain genome segments. These differences are known as copy number variations (CNVs). CNVs play an important role in determining the phenotype, or observable characteristics, of each individual.

One CNV located on the short arm of human chromosome 16 (16p11.2) occurs in approximately 1 in 1,000 individuals, and is among the most frequent causes of neurodevelopmental disorders. This CNV encompasses 30 annotated protein-encoding genes and is associated with autism, large head circumference and obesity when present in one copy. The presence of three copies is linked to schizophrenia, small head circumference and being underweight.

Alexandre Reymond and his collaborators Sébastien Jacquemont, Jacqui Beckmann and Bogdan Draganski at the University of Lausanne in Switzerland are enrolling individuals who carry 16p11.2 rearrangements in their genomes, and their family members, in a study involving more than 30 European cytogenetic centers.

Their aim is to better define the clinical profiles for both autism and schizophrenia. In order to minimize sampling biases inherent to certain recruitment methods, Reymond and his consortium plan to diversify enrollment criteria, for example by enrolling carriers of 16p11.2 CNVs from the general population. The strength of their approach lies in the cross-sectional and longitudinal data analyses and in the large number of participants examined.