A critical step to improving our understanding of autism spectrum disorder (ASD) is to identify underlying genetic and environmental risk factors. A number of rare copy number variants (CNVs) have emerged as robust genetic risk factors for ASD. However, not all individuals exhibit ASD and the severity of ASD symptoms varies among carriers of a CNV. Given that early therapeutic intervention attenuates symptoms, it is reasonable to assume that early environmental factors also influence ASD symptoms later. However, manipulation of the interplay between genetic and early environmental factors to identify mechanisms is difficult in humans. Our team is uniquely positioned to experimentally address this issue. First, we have identified atypical pup vocal call sequences of a genetic mouse model of ASD. To do so, our team applied a set of sophisticated statistical tools. Second, our team developed innovative experimental tools and demonstrated that such atypical pup call sequences induce less maternal approach. This observation shows that neonatal vocalization is a means of social communication with mothers and suggests that it influences the level of maternal care. Third, we found that enriched housing, an environmental manipulation known to reverse the detrimental behavioral effects of maternal separation in mice, alters the expression and methylation of a CNV-encoded gene in mouse brains. Capitalizing on these innovative methods and observations, we propose to test our central hypothesis that CNVs disturb neonatal social communication with the mother and this early experience exacerbates ASD-like behaviors via epigenetically modified expression of CNV- encoded genes. We will use mouse models of paternal 15q11-13 duplication, 15q13.3 hemizygosity and 22q11.2 hemizygosity, as they represent three robust genetic risk factors for ASD. Use of multiple models will allow us to determine common, as well as distinct roles of neonatal social communication in CNV-associated ASD. We propose to achieve the following three Aims:
Aim 1 : Determine if CNVs result in atypical vocalization structure during the neonatal period and if it is correlated with ASD-like behaviors at 2 months of age;
Aim 2 : Determine the impact of atypical neonatal vocalization on maternal care;
Aim 3 : Measure the effect of altered maternal care on the severity of ASD-like behaviors and CNV gene expression and epigenetic modification. The outcomes of this project will reveal the interplay between genetic factors and neonatal social communication with mothers resulting in the ultimate severity of ASD-like behaviors through epigenetic mechanisms. The project has high translational value because it could provide a novel mechanistic base to understand the gene-environment interaction underlying ASD.
Genetic risk factors do not necessarily result in autism and even when they do, severity varies widely among individuals. Given that early intervention modifies the severity of autism and that environmental factors are likely modifiers of outcome, this project will help establish how the interplay between genetic factors, early social communication, and neonatal maternal care determines the severity of autism-like behaviors via epigenetic mechanisms using three well-established mouse models of autism-associated genetic variants. The project has high translational value because it could provide mechanistic bases for symptomatic variability and lay the ground work for early therapeutic intervention.
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