Regulation of MET Expression in Autism Disorder and Forebrain Ontogeny

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DESCRIPTION (provided by applicant): There are two related long-term goals of the proposed research. First, we aim to determine the transcriptional regulators of a functional variant in the human MET promoter that is associated with autism spectrum disorder (ASD) vulnerability. Second, we plan to define the mechanisms through which the mouse Met receptor tyrosine kinase influences forebrain ontogeny. ASD is a significant neurodevelopmental disorder, with a prevalence of 1 in 150 in the United States, according to the Centers for Disease Control. Recently, we discovered that a single nucleotide polymorphism (SNP) in the 5' transcriptional regulatory region of the human MET gene (rs1858830 allele 'C') is strongly associated with ASD (P=5x10-6), and also reduces transcription factor (TF) binding and gene transcription. The convergence of data from human genetics studies in ASD and basic developmental neurobiology suggests that MET signaling is an important component for the assembly of forebrain circuits, with dysregulation leading to functional pathophysiology. We will first identify TFs that regulate MET expression. Our preliminary screen revealed 29 putative TFs, which we will validate by EMSA and ChIP assays. Over-expression and siRNA will be used to alter levels of MET-regulating TFs in vitro to delineate their individual and collective roles in regulating MET transcription. Next, we will use in situ hybridization in the mouse to establish the spatial and temporal expression of Met and its regulators during brain development. These maps are crucial for probing functional interactions that regulate Met transcription during cortical development. Finally, we will use a novel technical strategy, in utero electroporation in embryonic mice, to manipulate the expression of Lhx2, a putative Met-regulating TF, during brain development. The dual purpose of these manipulations is to reveal the effects of TF perturbation on Met expression in vivo and to define the ensuing impact on cortical development. RELEVANCE Autism spectrum disorder (ASD) is a serious neurodevelopmental disorder that impacts a large number of individuals, and also their families. We have identified a change in the MET gene that alters the way in which it is regulated and more than doubles the risk of ASD. MET is known to influence brain development, and we are studying the ways in which it is normally regulated in the brain, and how dysregulation may lead to altered brain development and increased ASD susceptibility. Our focus on regulation of MET is highly relevant to many health issues, as over-expression of the gene is characteristic of highly invasive malignancies, and our work shows that under-expression may be a risk factor for ASD.