Early expression of aromatase and the membrane estrogen receptor GPER in neuromasts reveals a role for estrogens in the development of the frog lateral line system

- The neuromast is the mechanosensory unit of the lateral line.
- High levels of the aromatase were detected in the mantle cells of neuromasts.
- Membrane estrogen receptors were localized to both the mantle and sensory hair cells.
- Pharmacological treatments activating GPER disrupt lateral line formation.
- Estrogens have a role in frog tadpole lateral line development.

Estrogens and their receptors are present at very early stages of vertebrate embryogenesis before gonadal tissues are formed. However, the cellular source and the function of estrogens in embryogenesis remain major questions in developmental endocrinology. We demonstrate the presence of estrogen-synthesizing enzyme aromatase and G protein-coupled estrogen receptor (GPER) proteins throughout early embryogenesis in the model organism, Silurana tropicalis. We provide the first evidence of aromatase in the vertebrate lateral line. High levels of aromatase were detected in the mantle cells of neuromasts, the mechanosensory units of the lateral line, which persisted throughout the course of development (Nieuwkoop and Faber stages 34-47). We show that GPER is expressed in both the accessory and hair cells. Pharmacological activation of GPER with the agonist G-1 disrupted neuromast development and migration. Future study of this novel estrogen system in the amphibian lateral line may shed light on similar systems such as the mammalian inner ear.