Epigenetic dysregulation of Oxtr in Tet1-deficient mice has implications for neuropsychiatric disorders
Aaron J. Towers, … , Wei Xie, Yong-hui Jiang
Aaron J. Towers, … , Wei Xie, Yong-hui Jiang
Published December 6, 2018
Citation Information: JCI Insight. 2018;3(23):e120592. https://doi.org/10.1172/jci.insight.120592.
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Research Article Genetics Neuroscience

Epigenetic dysregulation of Oxtr in Tet1-deficient mice has implications for neuropsychiatric disorders

Abstract

OXTR modulates a variety of behaviors in mammals, including social memory and recognition. Genetic and epigenetic dysregulation of OXTR has been suggested to be implicated in neuropsychiatric disorders, including autism spectrum disorder (ASD). While the involvement of DNA methylation is suggested, the mechanism underlying epigenetic regulation of OXTR is largely unknown. This has hampered the experimental design and interpretation of the results of epigenetic studies of OXTR in neuropsychiatric disorders. From the generation and characterization of a new line of Tet1 mutant mice — by deleting the largest coding exon 4 (Tet1Δe4) — we discovered for the first time to our knowledge that Oxtr has an array of mRNA isoforms and a complex transcriptional regulation. Select isoforms of Oxtr are significantly reduced in the brain of Tet1Δe4–/– mice. Accordingly, CpG islands of Oxtr are hypermethylated during early development and persist into adulthood. Consistent with the reduced express of OXTR, Tet1Δe4–/– mice display impaired maternal care, social behavior, and synaptic responses to oxytocin stimulation. Our findings elucidate a mechanism mediated by TET1 protein in regulating Oxtr expression by preventing DNA hypermethylation of Oxtr. The discovery of epigenetic dysregulation of Oxtr in TET1-deficient mouse brain supports the necessity of a reassessment of existing findings and a value of future studies of OXTR in neuropsychiatric disorders.

Authors

Aaron J. Towers, Martine W. Tremblay, Leeyup Chung, Xin-lei Li, Alexandra L. Bey, Wenhao Zhang, Xinyu Cao, Xiaoming Wang, Ping Wang, Lara J. Duffney, Stephen K. Siecinski, Sonia Xu, Yuna Kim, Xiangyin Kong, Simon Gregory, Wei Xie, Yong-hui Jiang

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Figure 4

Identification of Oxtr mRNA isoforms and reduced expression of Oxtr isoforms in Tet1Δe4–/– mice.

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Identification of Oxtr mRNA isoforms and reduced expression of Oxtr isof...
(A) Oxtr mRNA isoforms (A–H) identified by 5′ RACE and confirmed by RT-PCR and Sanger sequencing (predicted coding regions are shaded). qPCR primers indicated (multicolored arrows and supplemental method). The new sequences for individual isoforms have been deposited in GeneBank with accession no. KU686795-KU686801. (B) qPCR data revealed downregulation of isoform B, but not A or H, in the hippocampus of Tet1Δe4–/– mice (n = 3–4/group, *P < 0.05, 2-tailed t test). (C) The histone modification of Oxtr in mouse brain. The enrichment of histone H3K4me3 and H3K27me3 in BS1–BS3 regions of Oxtr was revealed from ENCODE project. A second putative regulatory element was identified within exon 3 (large black bar) of Oxtr, which overlaps a CpG island (green bar) (mm9, http://genome.ucsc.edu/). Selection of Oxtr regions for bisulfite sequencing (BS1–BS3) and ChIP-PCR are indicated. ENCODE ChIP data shown is from E14.5 whole brain produced in the laboratory of Bing Ren (H3K4me3, GEO GSM1000095; H3K27me3, GEO GSM1000143). The similar pattern is also observed in ChIP-seq from 8-week cerebellum (http://genome.ucsc.edu) (Supplemental Figure 6). (D) The enrichment of H3K4me3, H3K27me3, and H3K4me1 in DMRs of Tet1Δe4–/– mice. The hypermethylated DMRs (200 bp bin) in Tet1Δe4–/– cortex was selected firstly by Fisher test with a threshold of P < 0.05. The 2000 bp genomic windows containing at least 4 hypermethylated DMRs (200 bp) in Tet1Δe4–/– cortex were selected out as DMRs for histone enrichment analysis. Random control regions with same bin size covered by the same methylome were chosen as controls. The ENCODE ChIP-seq data from WT adult mouse neocortex was used for the analysis. P values (calculated by t test) indicate a significant differential histone enrichment between DMRs and control region. (E–G) ChIP-qPCR revealed altered histone modifications at the bivalent promoter region of and GARDP control (E) and Oxtr (F and G) in the cerebrum of Tet1Δe4–/– mice. H3K4me3 (active mark), H3K27me3 (repressive mark), and IgG (isotype negative control) were assessed in 2 regions overlapping coding exon 3 and exon 1 in the 5′ UTR. Both H3K4me4 and H3K27me3 were reduced in BS3 hypermethylated region of Tet1Δe4–/– mice (n = 2/group and 3 replicates for each group).