We have decades of expertise in the discovery of novel genetic intellectual disability and autism disorders. For some of these disorders, we have performed deep-phenotyping in large patient cohorts. In addition, we have studied a subset of these disorders in depth, including the fragile X syndrome with the aim of developing therapies for the patients. In these studies, we rely heavily on mouse models. We have studied many biochemical, electrophysiological and behavioral aspects of different animal models. In the fragile X syndrome, we have discovered that the inhibitory GABAergic neurons are compromised. Subsequently, we have corrected several of the abnormalities observed in disease animal models by adding drugs that interfere with the affected pathways. In the fragile X syndrome, our findings have led to the initiation of clinical trials in which we participated.