Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA275

Poster Communications

Calcineurin and Reelin Gene Promoter Region DNA Methylation Changes in the Amygdala of Young and Aged Rats

G. Ozturk1, C. Yazici Mutlu2, E. Akarsu3, O. Bayrak4, B. Yilmaz5, B. Seker5, O. Suakar4

1. Physiology, Istanbul Medeniyet University, Istanbul, Turkey. 2. Multidisciplinary Neuroscience, Ankara University, Ankara, Turkey. 3. Medical Pharmacology, Ankara University, Ankara, Turkey. 4. Medical Genetics, Yeditepe University, Istanbul, Turkey. 5. Physiology, Yeditepe University, Istanbul, Turkey.

DNA methylation, one of the important chromatin modifications of the epigenetic regulation, has been suggested to regulate the expression of genes involved in the formation of memory by preventing transcription. In this study, we aimed to investigate whether there is any age-related changes in DNA methylation and the effect of memory formation and storage on calcineurin (CaN) and reelin (RELN) gene promoter region DNA methylation in the amygdala region of the brain at different time points (1st hour, 24th hours, 7th days, 21st days). For this purpose, 123 Sprague-Dawley male rats, 63 for 3-4 months (250-350 g) and 60 for 19-20 months (400-500 g), were used. The contextual fear conditioning model was used to provide the formation of fear memory. The study groups were identified as controls(C), experiments (E) and naïve. The rats were decapitated immediately after freezing behaviour test. The amygdala region of the brain was isolated. DNA methylation changes in the promoter region of CaN and RELN genes were examined by MeDIP RT-PCR analysis method. The methylation level for each gene was determined as fold change relative to the naïve control. Data are compared by Student's t-test or non-parametric Mann-Whitney U test. The behavioral data show that fear memory formation is significantly observable at all time-points in young rats (C:58.10±18.30%; 56.89±9.33%; 52.74±16.65%; 63.08±15.75%, E:84.70±6.70%; 73.22±6.68%; 83.24±9.49%; 81.61±17.91%, p<0.05, respectively).On the other hand, fear memory formation was observed at the 24th hours and on the 21st days in the aged rats (C:34.81±10.74%; 48.96±17.29%, E:54.11±16.34%; 66.49±7.42%, p<0.05, respectively), but it was not occured at the 1st hour and on the 7th days (C:47.47±12.57%; 53.87±12.86%, E:52.55±25.15%; 61.21±20.65%, p>0.05, respectively). DNA methylation data indicate that CaN gene methylation decreased on the 7th and 21st days in the amygdala region of young rats (C:1.03±0.02; E:0.97±0.007, p<0.001, C:1.00±0.007; E:0.90±0.01, p<0.001, respectively), whereas it increased at the 1st and 24th hours in aged rats (C:0,92±0,02; E:0,97±0,01, p=0,01; C:0,89±0,05; E:1,00±0,03, p=0,005, respectively). RELN gene methylation decreased at the 1st hour and on the 7th days in the young rats (C:1.06±0.02; E:1.01±0.01, p=0.02, C:1.06±0.01; E:1.00±0.03, p<0.001, respectively) and increased at the 24th hours (C:0.99±0.01; E:1.04±0.01, p=0.002). However, no change was observed in the aged animals (p>0.05). As a result, our data show that the methylation levels of CaN and RELN genes change time dependency and age-related in the evaluated amygdala region during formation and storage of fear memory. These changes may be related with more general cellular regulation rather than a specific involvement with fear memory.

Where applicable, experiments conform with Society ethical requirements