PhD Scientific Days 2023

Neurosciences I.

Identification of Sex Steroid-Dependent Transcriptomic Changes in Kisspeptin Neurons of the Male Mouse

Text of the abstract

Introduction
Kisspeptin neurons of the arcuate nucleus (ARC), which regulate hypothalamic gonadotropin-releasing hormone secretion, are critical mediators of negative sex steroid feedback to the reproductive axis via molecular mechanisms still largely unknown. In males, the primary gonadal steroid hormone testosterone can regulate kisspeptin neurons via acting both on androgen receptors and, after being converted to estrogen (17β-estradiol) by the aromatase (Cyp19) enzyme, on estrogen receptors. In animal experiments, the non-aromatizable androgen hormone dihydrotestosterone (DHT) can be used to distinguish androgen receptor-mediated effects from the combined effects of testosterone on estrogen and androgen receptors.

Aims
Our work aimed to map the gene expression processes regulated by androgen and estrogen receptors in ARC kisspeptin neurons of male mice during negative feedback.

Method
Transgenic male mice were orchiectomized and supplemented with either 17β-estradiol (E2), DHT, testosterone (T), or vehicle (ORX). Intact males were used as an additional control. Fluorescently tagged kisspeptin neurons were collected from the ARC by laser-capture microdissection and used for cDNA library preparation and RNA-seq.

Results
Differential expression analysis identified thousands of transcripts that differed significantly between the 6 treatment groups. The androgen receptor-acting DHT regulated 1205 transcripts, whereas the estrogen receptor-acting E2 regulated 2080 transcripts compared with the ORX group. The steroid hormones changed the expression of transcription factors, ribosomal and mitochondrial proteins, ion channels, transporters, receptors, regulatory RNAs, and several neuropeptides, including Vgf. Comparison of these gene expression data to earlier results obtained from females revealed unexpected sex differences between the gonadectomized and the E2-treated models of the two sex.

Conclusion
Comprehensive characterization of the steroid hormone-dependent kisspeptin neuron transcriptome sheds light on the molecular mechanisms of gonads-brain communication and implicates additional neuropeptides and mechanisms in steroid feedback.

Funding
The research was supported by the New National Excellence Program of the Ministry for Culture and Innovation (ÚNKP-22-II-SE-10) and the National Research, Development, and Innovation Fund.