Ovarian hormones induce de novo DNA methyltransferase expression in the Siberian hamster suprachiasmatic nucleus

Abstract

The present study investigated neuroanatomically localised changes in de novo DNA methyltransferase expression in the female Siberian hamster (Phodopus sungorus). The objectives were to identify the neuroendocrine substrates that exhibit rhythmic Dnmt3a and Dnmt3b expression across the oestrous cycle and also examine the role of ovarian steroids. Hypothalamic Dnmt3a expression was observed to significantly increase during the transition from pro‐oestrous to oestrous. A single bolus injection of diethylstilbestrol and progesterone was sufficient to increase Dnmt3a cell numbers and Dnmt3b immunoreactive intensity in the suprachiasmatic nucleus. In vitro analyses using an embryonic rodent cell line revealed that diethylstilbestrol was sufficient to induce Dnmt3b expression. Up‐regulating DNA methylation in vitro reduced the expression of vasoactive intestinal polypeptide, Vip, and the circadian clock gene, Bmal1. Together, these data indicate that ovarian steroids drive de novo DNA methyltransferase expression in the mammalian suprachiasmatic nucleus and increased methylation may regulate genes involved in the circadian timing of oestrous: Vip and Bmal1. Overall, epigenetically mediated neuroendocrine reproductive events may reflect an evolutionarily ancient process involved in the timing of female fertility.

Prolactin Mediates Long-Term, Seasonal Rheostatic Regulation of Body Mass in Female Mammals

“…The PH was then separated from other brain structures by a transverse cut aligning the dorsal aspect of the optic tracts. This tissue dissection of the PH is specific to the arcuate nucleus and cells surrounding the third ventricle as evidenced by molecular localization demonstrated in our previous publication ( 37 ). All samples were returned to −70 °C until RNA extraction.…”

Abundance, efficiency, and stability of reference transcript expression in a seasonal rodent: The Siberian hamster

“…qPCR analyses are a common method used to assess photoperioddependent molecular changes in Siberian hamsters. Reference genes 18s [13][14][15], Act [16][17][18][19][20], Gapdh [15,18,19,21], Hrpt [14,15,17] and cyclophilin A [22] are frequently used reference genes within such analyses. To our knowledge, no study has systematically assessed the suitability of multiple reference genes across tissues and photoperiodic treatment.…”