LAUSR

Calcium (Ca2+) influx during oocyte maturation and after sperm entry is necessary to fill the internal Ca2+ stores and for complete egg activation. We knocked out the transient receptor potential vanilloid member 3 (TRPV3) and the T-type channel, CaV3.2 to determine their necessity for maintaining these functions in mammalian oocytes/eggs. Double knockout (dKO) females were subfertile, their oocytes and eggs showed reduced internal Ca2+ stores, and following sperm entry or PLCz cRNA injection, fewer dKO eggs displayed Ca2+ responses compared to wildtype (WT) eggs, which were also of lower frequency. These parameters were rescued and/or enhanced by removing extracellular Mg2+, suggesting the residual Ca2+ influx could be mediated by the TRPM7 channel, consistent with the termination of divalent-cation oscillations in dKO eggs by a TRPM7 inhibitor. In total, we demonstrated that TRPV3 and CaV3.2 mediate the complete filling of the Ca2+ stores in mouse oocytes and eggs. We also show they are required for initiating and maintaining regularly spaced-out oscillations, suggesting that Ca2+ influx through PM ion channels dictates the periodicity and persistence of Ca2+ oscillations during mammalian fertilization.