Gamete Biology

Meiotic Arrest in Human Oocytes Is Maintained by a G_s Signalling Pathway

Abstract
In mammalian oocytes, the maintenance of meiotic prophase I arrest prior to the surge of luteinizing hormone (LH) that stimulates meiotic maturation depends on a high level of cAMP within the oocyte. In mouse and rat, the cAMP is generated in the oocyte, and this requires the activity of a constitutively active, G_s-linked receptor, GPR3 or GPR12, respectively. To examine if human oocyte meiotic arrest depends on a similar pathway, we looked at whether human oocytes express the same components for maintaining arrest as rodent oocytes using RT-PCR and Western blotting. RNA encoding GPR3, but not GPR12, was expressed. RNA encoding adenylate cyclase type 3 (AC3), which is the major adenylate cyclase required for maintaining meiotic arrest in the mouse oocyte, was also expressed, as was Galpha_s protein. To determine if this pathway is functional in the human oocyte, we examined the effect of injecting a function blocking antibody against Galpha_s on meiotic resumption. This antibody stimulated meiotic resumption of human oocytes that were maintained at the prophase I stage using a phosphodiesterase inhibitor. These results demonstrate that human oocytes maintain meiotic arrest prior to the LH surge using a similar signalling pathway as rodent oocytes.

Key words: Gamete Biology • Cyclic adenosine monophosphate • Signal transduction

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