Neurogenetic disorders represent the largest category of Mendelian diseases in humans. They encompass a wide array of clinical presentations that range from the common e.g., intellectual disability (>1%) to the very rare, e.g., neurodegeneration with brain iron accumulation (one to three per 106) (Kalman et al., 2012 and Maulik et al., 2011). The highly prevalent involvement of the nervous system in many Mendelian disorders coincides with the observation that >80% of all human genes are expressed at some stage of brain development (Hawrylycz et al., 2012) and suggests that the brain is one of the most vulnerable organs to genetic perturbation. In fact high-resolution microarray analysis of the human genome reveals that intellectual disability is the common phenotypic denominator of genomic disorders that involve losses or gains of genes (Coe et al., 2012).