title: Conceptualizing neurodevelopmental disorders through a mechanistic understanding of fragile X syndrome and Williams syndrome.
abstract: OBJECTIVE
  The overarching goal of this review is to compare and contrast the cognitive-behavioral features of fragile X syndrome (FraX) and Williams syndrome and to review the putative neural and molecular underpinnings of these features. Information is presented in a framework that provides guiding principles for conceptualizing gene-brain-behavior associations in neurodevelopmental disorders.
  
  
  RESULTS
  Abnormalities, in particular cognitive-behavioral domains with similarities in underlying neurodevelopmental correlates, occur in both FraX and Williams syndrome including aberrant frontostriatal pathways leading to executive function deficits, and magnocellular/dorsal visual stream, superior parietal lobe, inferior parietal lobe, and postcentral gyrus abnormalities contributing to deficits in visuospatial function. Compelling cognitive-behavioral and neurodevelopmental contrasts also exist in these two disorders, for example, aberrant amygdala and fusiform cortex structure and function occurring in the context of contrasting social behavioral phenotypes, and temporal cortical and cerebellar abnormalities potentially underlying differences in language function. Abnormal dendritic development is a shared neurodevelopmental morphologic feature between FraX and Williams syndrome. Commonalities in molecular machinery and processes across FraX and Williams syndrome occur as well - microRNAs involved in translational regulation of major synaptic proteins; scaffolding proteins in excitatory synapses; and proteins involved in axonal development.
  
  
  CONCLUSIONS
  Although the genetic variations leading to FraX and Williams syndrome are different, important similarities and contrasts in the phenotype, neurocircuitry, molecular machinery, and cellular processes in these two disorders allow for a unique approach to conceptualizing gene-brain-behavior links occurring in neurodevelopmental disorders.
authors.affiliation: Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305–5719, USA.
authors.forename: Lawrence K
authors.initials: LK
authors.lastname: Fung
authors.forename: Eve-Marie
authors.initials: EM
authors.lastname: Quintin
authors.forename: Brian W
authors.initials: BW
authors.lastname: Haas
authors.forename: Allan L
authors.initials: AL
authors.lastname: Reiss
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000473:pathology; D003072:Cognition Disorders / Q000209:etiology*; D002658:Developmental Disabilities / Q000503:physiopathology*; D005600:Fragile X Syndrome / Q000150:complications* / Q000473:pathology / Q000523:psychology; D006801:Humans; D035683:MicroRNAs / Q000235:genetics; D009415:Nerve Net / Q000473:pathology; D059906:Neuroimaging; D013569:Synapses / Q000473:pathology; D018980:Williams Syndrome / Q000150:complications* / Q000473:pathology / Q000523:psychology
chemical_list: D035683:MicroRNAs