Schizophrenia-Like Phenotype Inherited by the F2 Generation of a Gestational Disruption Model of Schizophrenia

Abstract

Both environmental and genetic factors contribute to schizophrenia; however, the exact etiology of this disorder is not known. Animal models are utilized to better understand the mechanisms associated with neuropsychiatric diseases, including schizophrenia. One of these involves gestational administration of methylazoxymethanol acetate (MAM) to induce a developmental disruption, which in turn produces a schizophrenia-like phenotype in post-pubertal rats. The mechanisms by which MAM produces this phenotype are not clear; however, we now demonstrate that MAM induces differential DNA methylation, which may be heritable. Here we demonstrate that a subset of both second (F2) and third (F3) filial generations of MAM-treated rats displays a schizophrenia-like phenotype and hypermethylation of the transcription factor, Sp5. Specifically, ventral tegmental area of dopamine neuron activity was examined using electrophysiology as a correlate for the dopamine hyperfunction thought to underlie psychosis in patients. Interestingly, only a subset of F2 and F3 MAM rats exhibited increases in dopamine neuron population activity, indicating that this may be a unique model with a susceptibility to develop a schizophrenia-like phenotype. An increase in dopamine system function in rodent models has been previously associated with decreases in hippocampal GABAergic transmission. In line with these observations, we found a significant correlation between hippocampal parvalbumin expression and dopamine neuron activity in F2 rats. These data therefore provide evidence that offspring born from MAMtreated rats possess a susceptibility to develop aspects of a schizophrenia-like phenotype and may provide a useful tool to investigate geneenvironment interactions.

Comparative analysis of MBD-seq and MeDIP-seq and estimation of gene expression changes in a rodent model of schizophrenia

“…In our previous publication, 16 we reported on 181 genes (representing upstream and downstream genes of 92 DMRs). Although the updated rat genome and our alternate analysis protocol increased the number of DMRs detected, there was high concordance between DMRs identified in our previous publication and those identified here; 71% of the DMRs representing upstream and downstream genes in our initial study had overlapping DMRs that were also detected here, all of these showed the same direction of effect (data not shown).…”

“…16 The NEBNext Ultra TM DNA Library Prep Kit for Illumina was used to perform end repair, adapter ligation, and sample cleanup without size selection on 1 μg Covaris sheared DNA, according to the manufacturers’ protocol (starting volume 50 μl sheared DNA and 5.5 μl buffer EB). Unmethylated adapters (undiluted) obtained from the NEBNext Multiplex Oligos for Illumina Kit allowed for multiplexing of samples.…”

“…2014 (RGSC 6.0/rn6) assembly. To further compare our MeDIP-seq data analysis to our previous analysis, 16 , we converted the Rn5 DMR coordinates identified in our first study to Rn6 coordinates, using the UCSC genome database liftover functionality, and then looked for concordance between datasets.…”

“…11 Finally, the costs are similar for the two methodologies and we and others have developed protocols that allow for sample multiplexing. 11, 16 Previous reports favor MBD-seq as somewhat more sensitive (with sufficient coverage), however MeDIP demonstrates no bias for a specific nucleotide sequence and is constrained only by the methyl-CpG density within DNA fragments so it may provide better genome-wide coverage. 15, 17, 18 An additional drawback to MBD-seq is the lack of stable binding between MBD domain of MECP2 and hemimethylated DNA.…”

“…27, 28 More recently, we showed that a subset of F2 and F3 offspring also display a schizophrenia-like phenotype, and that widespread hippocampal DNA methylation changes were associated with in utero administration in both F1 and F2 progeny. 16 An increasing body of evidence suggests that the ventral hippocampus may represent a key site of pathology in schizophrenia. Indeed, hippocampal pathology is routinely observed in schizophrenia patients and is correlated with both psychosis 29 and cognitive dysfunction.…”