Sex-Specific Effects of Testosterone on the Sexually Dimorphic Transcriptome and Epigenome of Embryonic Neural Stem/Progenitor Cells

Abstract

The mechanisms by which sex differences in the mammalian brain arise are poorly understood, but are influenced by a combination of underlying genetic differences and gonadal hormone exposure. Using a mouse embryonic neural stem cell (eNSC) model to understand early events contributing to sexually dimorphic brain development, we identified novel interactions between chromosomal sex and hormonal exposure that are instrumental to early brain sex differences. RNA-sequencing identified 103 transcripts that were differentially expressed between XX and XY eNSCs at baseline (FDR = 0.10). Treatment with testosterone-propionate (TP) reveals sex-specific gene expression changes, causing 2854 and 792 transcripts to become differentially expressed on XX and XY genetic backgrounds respectively. Within the TP responsive transcripts, there was enrichment for genes which function as epigenetic regulators that affect both histone modifications and DNA methylation patterning. We observed that TP caused a global decrease in 5-methylcytosine abundance in both sexes, a transmissible effect that was maintained in cellular progeny. Additionally, we determined that TP was associated with residue-specific alterations in acetylation of histone tails. These findings highlight an unknown component of androgen action on cells within the developmental CNS, and contribute to a novel mechanism of action by which early hormonal organization is initiated and maintained.

Sexual dimorphisms in adult human neural, mesoderm‐derived, and neural crest‐derived stem cells

“…In line with the findings by Blankenhorn et al, reperfusion of infarcted rat hearts with female MSCs resulted in significantly increased recovery of left ventricular developed pressure compared to infarcted hearts treated with male MSCs [13]. Bramble et al [29,30] reported these transcriptional sex differences to be involved in cellular replication, indicating a differential regulation of proliferative and stemness states between male and female NSCs during development. Thus, intrinsic mechanisms defined by the sex seem a biologically relevant aspect of the protective and regenerative power of adult stem populations [13,14].…”

“…Bramble et al [29,30] revealed 103 differentially expressed transcripts between male and female murine embryonic neural stem cells using global gene expression analysis. Bramble et al [29,30] revealed 103 differentially expressed transcripts between male and female murine embryonic neural stem cells using global gene expression analysis.…”

“…As introduced above, differences between the sexes in neuronal development can be also directly observed on cellular level prior to gonadal-derived hormonal surges. Bramble et al [29,30] revealed 103 differentially expressed transcripts between male and female murine embryonic neural stem cells using global gene expression analysis. Transcriptional sex differences were mostly involved in cellular replication, indicating a differential regulation of proliferative and stemness states between male and female embryonic NSCs during development.…”

“…Here, a global gene expression analysis of murine embryonic neural stem cells (NSCs) revealed 103 differentially expressed transcripts between male and female NSCs prior to gonadalderived hormonal surges. Bramble et al [29,30] reported these transcriptional sex differences to be involved in cellular replication, indicating a differential regulation of proliferative and stemness states between male and female NSCs during development. These observations in the adult organism as well as within early mammalian development evidence the existence of stem cell-intrinsic sex differences in addition to already described effects of hormones.…”

Neuroimmunology and neuroepigenetics in the establishment of sex differences in the brain

“…When compared before the onset of gonadal steroid production, more than 100 transcripts were differentially expressed between female (XX) and male (XY) stem cells. Intriguingly, stem cells of both sexes were responsive to testosterone treatment but not in the same way: thousands more transcripts varied in response to testosterone in XX stem cells than in XY stem cells 17 .…”