SAS1B protein [ovastacin] shows temporal and spatial restriction to oocytes in several eutherian orders and initiates translation at the primary to secondary follicle transition (pages 1405–1426)
Eusebio S. Pires, Callie Hlavin, Ellen Macnamara, Khadijat Ishola-Gbenla, Christa Doerwaldt, Catherine Chamberlain, Kenneth Klotz, Austin K. Herr, Aalok Khole, Olga Chertihin, Eliza Curnow, Sandford H. Feldman, Arabinda Mandal, Jagathpala Shetty, Charles Flickinger and John C. Herr
Version of Record online: 2 OCT 2013 | DOI: 10.1002/dvdy.24040
- SAS1B protein is highly conserved in primary sequence and the ASTL gene is tightly regulated across eutherians, showing an identical immunohistochemical profile of ovarian expression and oocyte restriction among adult tissues, and a similar ∼44 to 55 kDa range of apparent protein masses.
- SAS1B is first translated in ooplasm of follicles undergoing the primary-secondary follicle transition; quiescent germ cells in primordial follicles and early growing oocytes in primary follicles show no evidence of SAS1B protein translation in any species studied.
- SAS1B is concentrated in the microvillar domain on the egg plasma membrane in species in which this feature is well developed. In species such as macaque, SAS1B shows a uniform distribution on the plasma membrane of GV oocytes.
- A population of SAS1B is concentrated in cortical granules within mature oocytes indicating that the protein reaches the cell surface and redistributes on the oolemma and in the perivitelline space through exocytosis.
- Due to SAS1B's oocyte specificity, restriction to growing oocytes, absence in the ovarian reserve, oolemmal localization, and wide distribution across eutherian species this metalloprotease is proposed as a candidate target for developing reversible nonhormonal female contraceptive agents in a range of mammalian species and may serve as a useful biomarker for growing oocytes that have entered the primary-secondary follicle transition and beyond.