Abstract
The development of the embryonic brain is a critical process, and neurodevelopment
disorders, such as attention deficit hyperactivity disorder, autism, and schizophrenia, can
arise due to dysregulation during neurodevelopment. However, the cause for these disorders and
the generation of sex differences displayed between the disorders are still largely
unknown research areas. Current theories of contribution towards sex differences generated
in neurodevelopment disorders suggest the dysregulation of miRNAs, a small non-coding
RNA essential for neurodevelopment that negatively regulates mRNA.
A significant contribution to sex differences is hormones such as estrogen. An enzyme,
aromatase, can convert testosterone to estrogen, and due to the early secretion of testosterone
by the testis during development means that higher estrogen levels are found in males.
Estrogen binds to the estrogen receptor, which can bind to gene regulatory elements to
influence gene expression. Thereby, due to the role estrogen plays in the generation of sex
and regulation, we suggest that estrogen has a role in regulating sex-biased miRNA gene
expression.
Here I have investigated the relationship between estrogen and miRNA in the embryonic
wild-type E15.5 mouse brain by chromatin immunoprecipitation followed by Real-Time
quantitative PCR. Potential regulatory DNA elements near seven miRNAs were investigated,
and the results demonstrated sex differences in the recruitment of two estrogen receptors,
Estrogen receptor 1 and Estrogen receptor 2. Recruitment of ERα was significant in the
females, while ERβ bound significantly for the males for the miRNAs; miR-10b-5p, miR199a-5p, miR-200a-5p, miR-205-5p, and miR-206-3p.
To further confirm if our investigated miRNAs were regulated by estrogen, E13.5 mice brain
tissues were cultured and treated with β-estradiol. Four of the investigated miRNAs, miR10b-5p, miR-200c-3p, miR-205-5p, and miR-206-3p, showed significant responses following
the addition of 17β-estradiol, and the response differed between the sexes. Females
responded positively, while males responded negatively in addition to β-estradiol.
This study provides further evidence for using different estrogen receptor types between the
sexes and that for three investigated, miRNAs are regulated by estrogen. This provides
evidence for a potential link between estrogen and miRNA gene regulation in the generation
of sex differences during neurodevelopment.