Research Projects

DNA methylation mediated by DNA methyltransferases (DNMTs) and covalent modifications of histones due to histone deacetylases (HDACs), histone acetyltransferases (HATs), histone methyltransferases (HMTs) etc. are the most-well studied epigenetic modifications in mammals. Functionally, DNMTs interact with HDACs and HMTs to cooperatively mediate gene silencing. Given their central role in normal development, it is not surprising that aberrant epigenetic modifications are observed in disease conditions. Specifically, in case of schizophrenia (SZ), aberrant DNA methylation, histone modification patterns as well as increased levels of DNMT1, DNMT3A and HDAC1, but reduced levels of HDAC2 were reported. However, mechanisms by which altered levels of these enzymes result in SZ-associated phenotypes is not well understood. Since de novo methylation also requires DNMT3B, we hypothesize that overexpression of all three DNMTs is required for aberrant DNA methylation of the promoters of SZ-associated genes. Since overexpression of DNMT1 results in embryonic lethality and precludes generation of appropriate animal models, we recently proposed that genetically modified embryonic stem cells (ESCs) overexpressing DNA methylation machinery serve as useful models to study neurodevelopmental abnormalities associated with SZ. We have so far been successful in generating and characterizing mouse ESC lines overexpressing both DNMT1 and DNMT3A. These cell lines produce abnormal neurons with dysregulation of genes associated with multiple neurological disorders. Here we propose to (1) Develop mouse ESC lines that overexpress all three DNMTs to study the molecular effects on neurogenesis, and (2) Test whether the molecular defects caused by DNMT overexpression can be corrected by increasing the expression of HDAC2 or decreasing the expression of HDAC1. Towards this, Wild-type and mutant ESCs, and their neuronal derivatives will be subjected to DNA methylome and transcriptome sequencing to identify the affected genes and pathways. The transgenic lines will then be used to either overexpress HDAC2 or silence HDAC1 to determine whether modulating HDAC expression can rectify the neurodevelopmental defect. The proposed project will provide important insights into the roles of HDACs and DNMTs in abnormal neurodevelopment and disorders such as schizophrenia, intellectual disability and Alzheimer’s wherein epigenetic abnormalities have been reported. The triple transgenic lines proposed to be developed are unique, expected to be showing dysregulation of multiple candidate genes influencing abnormal neurodevelopment and can serve as useful tools for developing and screening drugs for treatment of neurological disorders. These cell lines can also be used to develop DNMT/HDAC isoform-specific inhibitors to test their efficacy in reducing the neurodevelopmental defect.