Studying child development in genetic models of ASD.

This chapter approaches the early development in autism spectrum disorder (ASD) through comparative study of some key monogenic syndromic models of ASD in humans. Using this method, as well as referring to relevant work in idiopathic ASD, we address three complimentary areas: (i) patterns of ASD behavioral phenotype expression across genetic syndromes, as a way of addressing gene-phenotype correlations; (ii) longitudinal developmental trajectories toward autism in early childhood, as a way of addressing developmental specificity; and (iii) experimental intervention trials, for treatment and mechanism discovery. The comparative approach does not highlight striking phenotypic specificity, but early studies were often limited and more methodologically sophisticated recent studies may suggest subtle distinctions. Longitudinal studies are at an early stage but can build on the substantive work on early prodromal development of idiopathic ASD. Translational intervention trials to date have not found candidate treatments and we argue that a new generation of more ambitious experimental mechanism trials is needed. This field now has the opportunity to combine comparative prospective longitudinal developmental studies with in-depth cross-syndrome phenotyping and linked ambitious targeted mechanistic interventions in a way that could be mutually informing and maximize the potential of syndromic models to illuminate the pathophysiology of ASD.