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 3

Tet1Δe4–/– mice show hypermethylation of the Npas4 and Oxtr CpG islands during early development and complex transcriptional dysregulation of Oxtr.

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Tet1Δe4–/– mice show hypermethylation of the Npas4 and Oxtr CpG islands...
(A) Diagram of Npas4 promoter (coding regions are shaded), associated CpG island (green bar), and bisulfite-sequencing region (black bar). Npas4 was hypermethylated in hippocampus of Tet1Δe4–/– mice (n = 3/group; P = 0.004, 2-tailed t test). Blue squares represent unmethylated CpG dinucleotides, red squares represent methylated CpGs, and white squares were undetermined due to the ambivalent sequence reads and the same for other figures. (B) Diagram of Oxtr gene structure (coding regions are shaded), CpG island (green bar), and bisulfite-sequencing regions (BS, black bars). The genomic coordinate of BS1–BS3 in mouse mm9 assembly are as follows: BS1, Chr6:112440814-112441327; BS2, Chr6:112440387-112440815; BS3, Chr6: 112439019-112439542. The human CpG island spans 2319 bp (hg19:Chr3:8808962-8811280) extending to the more 5′ region of OXTR as indicated by a dotted green line. Mouse CpG island is 859 bp (mm9:Chr6:112439019-112439877). Human promoter MT2 region (9) and the region harboring the CG site that is likely to be equivalent to the human –934 CG site (14) are indicated as arrow. BS2 and BS3 were hypermethylated but not BS1 in hippocampus of adult Tet1Δe4–/– mice (n = 3/group; BS2, P = 0.0015; BS3, P = 0.0000015; 2-tailed t test). BS3 showed intermediate levels of hypermethylation in Tet1Δe4+/– mice (n = 3–4/group; P = 0.0019, 2-tailed t test). (C) Quantification of DNA methylation of BS1, BS2, and BS3 in hippocampus of Tet1+/+ and Tet1Δe4–/–. (D) The hMDeIP shows the comparable level of 5hmC in BS3 between Tet1+/+ and Tet1Δe4–/– (n = 5/group; **P < 0.005; ***P < 0.0005; 2-tailed t test).(E) Oxtr BS3 was not hypermethylated in Tet1Δe4–/– ESCs. (F) Oxtr BS3 was hypermethylated in cerebellum (CB), cortex (CX), and olfactory bulb (OB) of adult Tet1Δe4–/– adult mice. (G) Oxtr BS3 was hypermethylated in E14.5 cerebellum of Tet1Δe4–/– mice. (H) Oxtr BS3 was hypermethylated in tissues of heart and lung from the other 2 germ layers (Meso, mesoderm; Endo, endoderm). (I) Whole-genome bisulfite sequencing of neocortex from adult brain of Tet1Δe4–/– mice revealed Tet1-DMRs are significantly enriched in intragenic CpG islands (CGI) (n = 3 for +/+ and –/–; P = 2.65 × 10–38, Fisher’s exact test).