DNA methylation is important for proper neuronal development and improper DNA methylation is associated with numerous neurological disorders such as autism and intellectual disability. The proposed research will utilize genomic approaches to examine how disease mutations in DNA methyltransferase 3a (DNMT3A) lead to altered neuronal methylation and investigate how loss of DNMT3A affects neuronal transcription. This work will establish how DNMT3A functions in healthy and diseased neurons to carefully regulate transcription in a cell-type-specific manner.
Human genetic studies have linked intellectual disability to disruption of genes encoding epigenetic factors, but little is known about how a variety of different disease mutations disrupt protein function to lead to disease. DNA methyltransferase 3a (DNMT3A) functions to add methyl groups to cytosines in DNA, and mutations in DNMT3A are associated with a neurodevelopmental disorder with intellectual disability known as Tatton-Brown-Rahman Syndrome (TBRS). Though DNA methylation is classically considered to only occur in mammalian cells in the CpG context, neurons have high levels of a recently-discovered form of methylation in non-CpG contexts established by DNMT3A. This non-CpG methylation, primarily occurring at CA dinucleotides (mCA), is critical to proper neuronal development, as it is necessary for establishment of neuronal cell-type-specific transcription. Though mCA plays an important role regulating neuronal gene expression, little is known about how loss of DNMT3A and mCA relate to neurodevelopmental disease. Additionally, it is unknown how mutations within the three conserved protein domains of DNMT3A each mechanistically lead to loss of mCA. In this proposal, I will determine how disease mutations in the chromatin targeting domains of DNMT3A impact protein function and demonstrate how DNMT3A disruption alters neuronal transcription. In Aim 1, I model disease mutations identified in TBRS studies and analyze how disease mutations within different protein domains differentially affect targeting to the genome and methyltransferase activity to alter mCA build-up. This will define the mechanisms leading to disease and provide insight into the functional domains of DNMT3A. In Aim 2, I will explore how loss of DNMT3A differentially affects specific neuronal cell-types, dissecting out how the epigenome and transcriptome are changed during maturation of Parvalbumin positive interneurons and Somatostatin positive interneurons. This analysis will begin to uncover how disruption of DNMT3A affects specific cell types and will result in target genes such as ion channels or receptors to further study functional cellular outcomes. Together, these analyses will elucidate the function of DNMT3A and mCA in neurons and mechanistically link them to neurodevelopmental disease.
