TMEM16A Contributes to Calcium-Activated Chloride Currents and Membrane Potential Changes in the Mouse Oocyte.

Area of Science:

• Reproductive Biology
• Cell Physiology
• Ion Channel Function

Background:

• Intracellular calcium oscillations ([Ca2+]i) drive mouse oocyte activation and membrane potential (Em) hyperpolarizations post-fertilization.
• The specific ion channels responsible for these Em hyperpolarizations remain unidentified.

Purpose of the Study:

• To identify the ion channels mediating membrane potential hyperpolarizations in mouse oocytes.
• To investigate the role of these channels in early embryonic development.

Main Methods:

• Utilized thimerosal to mimic fertilization-induced [Ca2+]i oscillations and Em changes.
• Applied specific inhibitors for calcium-activated chloride channels (CaCC), including TMEM16A inhibitors (T16Ainh-01), and blockers for other ion channels (TEA, 9AC).
• Assessed TMEM16A protein expression and localization in oocytes and evaluated the impact of TMEM16A inhibition on zygote development.

Main Results:

• Thimerosal-induced Em and [Ca2+]i changes were significantly inhibited by CaCC blockers (DIDS, NFA, T16Ainh-01).
• Potassium and voltage-gated chloride channel blockers did not affect these changes.
• TMEM16A protein is expressed in mouse oocytes and localized to the plasma membrane.
• Inhibition of TMEM16A during zygote culture blocked development to the blastocyst stage.

Conclusions:

• This study provides the first evidence that TMEM16A-containing CaCC channels are critical for initiating membrane potential hyperpolarizations in mouse oocytes.
• TMEM16A plays a vital role in early mouse oocyte function and embryonic development.