Estrogen-related receptor is critical for testicular mitochondrial homeostasis and sperm motility: a Drosophila-based study.

Objective: To study the role of estrogen-related receptors (ERRs) in testicular function, with particular emphasis on mitochondrial homeostasis, testicular steroidogenesis, and sperm motility using Drosophila as a model.

Design: Experimental study.

Setting: Academic research laboratory.

Animal(s): Wild-type and transgenic strains of Drosophila melanogaster.

Intervention(s): Using a ribonucleic acid interference-based approach, ERR was knocked down specifically in the testes to generate Drosophila males with reduced ERR levels in their testes. Genetically matched sibling males without the knockdown formed the controls.

Main Outcome Measure(s): Analysis of the testicular mitochondrial structure and function in relation to energy production, steroidogenesis, and sperm motility in Drosophila.

Result(s): Depletion of ERR affects mitochondrial homeostasis (biogenesis, fission, fusion, mitophagy, and transport) and oxidative respiration in the testes. Consequently, ERR knockdown testes have significantly reduced mitochondrial size, mass, and depleted adenosine triphosphate levels resulting in testicular oxidative stress. Further, Halloween genes, associated with steroidogenesis in Drosophila, are misregulated in ERR knockdown testes, and knockdown of some of the steroidogenic genes in a testis-specific manner results in significantly reduced fertility. In addition, sperm from ERR knockdown testes have significantly reduced levels of glucose transporter, Na+K+ ATPase, Dynein heavy chain, and adenosine triphosphate-5α synthase essential for sperm function. Corroborating this, sperm from ERR knockdown males are significantly less motile compared with control.

Conclusion(s): The ERR is crucial for meeting the cellular energy requirements of the testes and the generation of normal motile sperm and hormone synthesis/secretion in the testes. To our knowledge, this is the first report implicating ERR in these ultimate functions of the testes. These findings can potentially contribute to the etiologic understanding of asthenozoospermia or infertility at large in men.