Characterization, relative abundances of mRNA transcripts, and subcellular localization of two forms of membrane progestin receptors (mPRs) in the common Chinese cuttlefish, Sepiella japonica.

The membrane progestin receptor (mPR) family has been characterized in several species, including fish, frogs, rats, and humans. Results of previous studies indicate mPRs mediate the rapid, nongenomic action of progestins. In this study, the full-length cDNA of Sepiella japonica mPR-beta (mPRβ) and mPR-gamma (mPRγ) were characterized. Furthermore, sjmPR mRNA relative abundances were assessed for different tissues. There was also determination of the subcellular localization of mPRs, and investigation of the effect of sjmPRs on ovarian development via proximate actions on the brain and ovary of S. japonica. Results of tissue distribution assays indicated mPRβ and mPRγ transcripts were present predominantly in the brain and ovary. As ovaries developed, the abundance of SjmPRs mRNA transcripts increased and peaked during the interstitial growth phase (III), followed by a marked decrease afterward in both the brain and ovary. In addition, confocal microscopy evaluations of HEK293 T cells expressing the mPRs-EGFP gene indicated both SjmPRβ and SjmPRγ were localized in the plasma membrane of HEK293 T cells. Taken together, these findings indicate S. japonica protein is a membrane progestin receptor capable of inducing ovary maturation in cephalopods.