Neurogenesis in the neonatal rat hippocampus is regulated by sexually dimorphic epigenetic modifiers

Abstract

Background Neurogenesis in the hippocampus endures across the lifespan but is particularly prolific during the first postnatal week in the developing rodent brain. The majority of new born neurons are in the dentate gyrus (DG). The number of new neurons born during the first postnatal week in the DG of male rat pups is about double the number in females. In other systems, the rate of cell proliferation is controlled by epigenetic modifications in stem cells. We, therefore, explored the potential impact of DNA methylation and histone acetylation on cell genesis in the developing DG of male and female rats. Methods Cell genesis was assessed by quantification of BrdU + cells in the DG of neonatal rats following injections on multiple days. Methylation and acetylation were manipulated pharmacologically by injection of well vetted drugs. DNA methylation, histone acetylation and associated enzyme activity were measured using commercially available colorimetric assays. mRNA was quantified by PCR. Multiple group comparisons were made by one- or two-way ANOVA followed by post-hoc tests controlling for multiple comparisons. Two groups were compared by t test. Results We found higher levels of DNA methylation in male DG and treatment with the DNA methylating enzyme inhibitor zebularine reduced the methylation and correspondingly reduced cell genesis. The same treatment had no impact on either measure in females. By contrast, treatment with a histone deacetylase inhibitor, trichostatin-A, increased histone acetylation in the DG of both sexes but increased cell genesis only in females. Females had higher baseline histone deacetylase activity and greater inhibition in response to trichostatin-A treatment. The mRNA levels of the proproliferative gene brain-derived neurotrophic factor were greater in males and reduced by inhibiting both DNA methylation and histone deacetylation only in males. Conclusions These data reveal a sexually dimorphic epigenetically based regulation of neurogenesis in the DG but the mechanisms establishing the distinct regulation involving DNA methylation in males and histone acetylation in females is unknown.

Diabetic Retinopathy and Regulation of Mitochondrial Glutathione–Glutathione Peroxidase Axis in Hyperhomocysteinemia

“…The nuclear pellet was suspended in NE1 buffer containing dithiothreitol and protease inhibitors (1:1000 each) and centrifuged at 11,000× g for one minute. The final nuclear pellet was suspended in the extraction buffer, incubated on ice for 15 min and sonicated for 3 × 10 s. The suspension was then centrifuged at 12,500× g for 10 min, and the supernatant was used for quantifying the enzyme activity of Dnmt [ 31 ].…”