Brown Rats Early Social Environment For The Vlar Gene Expressed In Specific Brain Regions And Research On The Effects Of The Promoter Region Methylation

Pair-bond and social bond are important behavioral characteristics in animals and human being. Previous studies suggest that V1aR gene plays a critical role in the regulation of monogamous social behaviors. However, recent studies found that voles with the same promoter structure of the V1aR gene display significant differences in mating system and social behavior. Hence, the association between monogamous social behavior and V1aR gene is still not well understood. Behavioral epigenetic research and our preliminary studies proposed that the interactions between V1aR gene and early environment may regulate monogamy social behavior. The present study mainly tried to answer following questiones:whether different level and mode of parental investments affect V1aR gene expression; whether different parental investments affect V1aR gene methylation; whether different investment levels and different parental patterns affects the distribution of V1aR receptor. In order to reveal the molecular biological mechanism underlying formation of pair-bonds and social bonds, we explore the epigenetic mechanism underlying association between different parental investment and expression and methylation of V1aR gene which is believed to be involved in monogamous pair bonding. Objective:We explore whether early social experience regulate the the brain V1aR DNA gene methylation and mRNA expression in the specific brain regions (Lateral septal nucleus; Ventral pallidum; Paraventricular hythalamic nucleus) which is associated with monogamous pair bonding in mandarin voles (Microtus mandarinus). Method:Mandarin voles were randomly assigned to3groups, Biparental care group (PC); paternal deprivation group (PD); Early social deprivation (ED). Our study adopt real-time quantitative PCR to examine the levels of the V1aR mRNA expression in the LS, VP, the PVN of adult mandarin vole neonatally exposed to different social environments.We also employ bisulfite sequence technique to identify the different methylation statute among promoter region of V1aR DNA gene following treatment with sodium bisulfite (NaHSO3) in mandarin voles from different groups. Results:1. Sequence analysis of V1aR gene promoter region and exon1.1316bp sequence in the V1aR gene promoter regions and1090bp sequence in the V1aR gene exon regions were cloned. These two fragments were combined into V1aR5’ ultral fragment2295bp sequence. Through analysis, we predicted that there are3potential CpG islands with lengths of363bp,263bp and555bp. The three CpG islands contain25,25and48CpG sites respectively.2. Effects of early social environment on V1aR mRNA expression in the LS, VP and PVN in adult mandarin vole.Compared to the PC group, the expression of V1aR mRNA in LS and the VP regions of the brain dramatically decreased in male voles of PD group. The results indicated that the different parental investment significantly affected the type V1aR receptor expression in voles. The levels of V1aR mRNA expression in VP and PVN were significantly higher in PC than those in ED group. We suggested that the different levels of parental investment impact V1aR mRNA expression in the brain regions associated with mating system.3. Methylation analysis of V1aR gene promoter region:Hypomethylation of CpG islands in V1aR gene5’non-coding region region was found in brain regions. Hypermethylation of CpG islands in V1aR gene the exon1region was found in specific brain region following ED and PD treatment that is possibly associated with regulation of pair bonding.4. In the LS, methylation status of V1aR gene5’ non-coding region was associated with mRNA expression of V1aR gene. In VP and PVN, there was no significant correlation between the methylation status of V1aR gene5’ non-coding region and mRNA expression of the gene. Conclusion:The V1aR gene promoter region in mandarin vole was predicted to include one CpG islands with25CpG sites and was found to display the low level of methylation. Methylation was found to exist in23,24CpG islands in the LS,1,20,25CpG sites in the VP, and11CpG sites in the PVN in the PC group. All of the other loci did no show significant difference in the methylation values. And he methylation is possibly associated with early social environments.The levels of V1aR mRNA expression were affected by early social environments such as PC, PD and ED.We suggest that different early life environment had critical effects on the relative receptor densities in brain region associated with mating system in mandarin voles. The levels of the V1aR receptor expression in specific brain regions of mandarin vole is closely related to the early social environment. These effects are possibly not due to the methylation status of vole V1aR gene5’ non-coding region, but by methylation status of exon1region.