Genome-wide screening methods identify a rapidly increasing number of common single nucleotide polymorphisms (SNP) as well as rare mutations, both inherited and de novo, such as single nucleotide (SNV) and copy-number variants (CNV) associated with attention-deficit/hyperactivity disorder (ADHD).
We performed whole-exome sequencing (WES) of several affected members of 8 extended pedigrees with a high density of ADHD followed by segregation analysis of candidate variants. Preliminary results indicate no clear segregation patterns of individual variants suggesting more complex, oligogenic disease etiology. The diversity of ADHD-related phenotypes supports the hypothesis of extensive genetic heterogeneity, which excludes the interfamilial combining of sequencing data and suggests that every family has to be considered individually.
With the implementation of high-throughput sequencing technologies it is to be expected that the number of putatively pathogenic mutations causing ADHD will further increase in the next years. This is likely to lead to the identification of multiple functional relationships between gene products and the emergence of common molecular and cellular pathways towards disease. Potential candidates are genes involved in synaptogenesis and synaptic plasticity. These common pathways will allow refined subtyping of ADHD into population- or even family-specific syndromes and will provide attractive opportunities for knowledge-based personalised therapeutic interventions.