Orai1 mediates store-operated Ca2+ entry during fertilization in mammalian oocytes

Dev Biol. 2012 May 15;365(2):414-23. doi: 10.1016/j.ydbio.2012.03.007. Epub 2012 Mar 15.


The presence of the store-operated Ca(2+) entry channel Orai1 and its function in signal transduction during fertilization have been investigated in mammalian oocytes using the pig as a model. RT-PCR cloning and sequence analysis revealed that Orai1 is expressed in the oocytes with a coding sequence of 921bp. After indirect immunocytochemistry or the overexpression of EGFP-tagged Orai1, the fluorescent signal was present primarily in the cell cortex consistent with plasma membrane localization of the protein. Western blot and real-time PCR results showed that Orai1 expression decreases during oocyte maturation; this is associated with the oocytes gaining the ability to generate a large Ca(2+) influx after store depletion. Downregulation of Orai1 expression by siRNA microinjection blocked Ca(2+) influx after store depletion and subsequent Ca(2+) add-back; the Ca(2+) oscillations induced by the fertilizing sperm were also inhibited in oocytes with downregulated Orai1 levels. At the same time, overexpression of Orai1 in the oocytes also modified store-operated Ca(2+) entry and had an inhibitory effect on the fertilization Ca(2+) signal. The abnormal Ca(2+) signaling due to Orai1 downregulation had a strong negative impact on subsequent embryo development. Co-overexpression of Orai1 and STIM1 on the other hand, led to a dramatic increase in Ca(2+) entry after store depletion. The findings indicate that Orai1 is a plasma membrane-resident Ca(2+) channel that is responsible for mediating Ca(2+) entry after the mobilization of intracellular Ca(2+) in oocytes. Orai1 and a functional store-operated Ca(2+) entry pathway are required to maintain the Ca(2+) oscillations at fertilization and to support proper embryo development.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism*
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Calcium Signaling*
  • Cells, Cultured
  • Fertilization in Vitro
  • Fertilization*
  • Molecular Sequence Data
  • Oocytes / metabolism*
  • Swine


  • Calcium Channels
  • Calcium