Oscillations in intracellular Ca2+ Ca2+i are essential for mouse oocyte activation following fertilization. These Ca2+i oscillations also induce repetitive hyperpolarizations in the membrane potential (Em). The present study aimed to identify the channels underlying the Em hyperpolarizations. Sulfhydryl reagents such as thimerosal, that oxidize the IP3-R channel, mimic the physiological changes at fertilization by eliciting simultaneous Em changes and Ca2+i oscillations. Thimerosal-induced Em and Ca2+i changes were prevented by the non-specific Ca2+-activated Cl- channel (CaCC) inhibitors DIDS and NFA, as well as the TMEM16A/Anoctamin 1 CaCC specific inhibitor, T16Ainh-01. The K+ channel blocker TEA, and voltage-gated Cl- channel blocker 9AC failed to inhibit the Em or Ca2+i changes. TMEM16A protein was expressed in all stages of mouse preimplantation development, being localized at the plasma membrane in oocytes. Culture of zygotes in the TMEM16A inhibitor prevented development to the blastocyst stage. In summary, we present the first evidence for CaCC channels, namely TMEM16A, being critical for the initiation of Em hyperpolarisations in mouse oocytes.
Dalati et al. (Sun,) studied this question.