Sex bias in the prevalence of various neurodevelopmental disorders suggests that differences in sex development may leave one sex more susceptible to disease. Subtle differences between the developing male and female brain can be driven by modulating gene expression levels. MicroRNAs (miRNAs), a class of small, non-coding RNAs, function to finely tune gene expression levels but little is known about their role in sex-dimorphic brain development.
We hypothesised that sex-differential miRNA expression occurs during mouse brain development. Small RNA sequencing was performed with RNA isolated from E15.5 mouse brains. Differences in expression were validated using real time quantitative RT-qPCR adapted for miRNA quantification using the PolyA tailing method.
We found 12 miRNAs to be significantly differentially expressed between the sexes (n=3 per sex, Padj < 0.05). RT-qPCR confirmed differential expression of a portion of these miRNAs, including miR-10, encoded within the Hox gene locus. LNA in situ hybridisation targeting miR-10 showed high expression in the hindbrain and anterior spinal cord of embryos at E15.5. As miRNAs are expressed in a temporally specific manner, novel miRNAs may be specific to the developing mouse brain. Further deep sequencing aims to discover novel miRNAs throughout the genome.
Future work aims to explore the causes and consequence of sex-dimorphic miRNA expression. How embryo sex determines miRNA expression will be investigated by manipulating hormone levels. To confirm predicted target mRNAs I will use luciferase reporter assays. Ultimately, we aim to compare wildtype brain with a knock-out line for a miRNA of interest.