Activation of cumulus-free mouse oocytes

Area of Science:

• * Reproductive Biology
• * Developmental Biology
• * Mammalian Oocyte Activation

Background:

• * Parthenogenetic activation of mammalian oocytes is crucial for assisted reproductive technologies, including cloning.
• * Successful activation typically requires specific chemical or electrical stimuli, often in the presence of surrounding cumulus cells.
• * Activating cumulus-free oocytes presents a significant challenge for efficient nuclear transfer procedures.

Purpose of the Study:

• * To investigate effective parthenogenetic activation methods for cumulus-free oocytes from random-bred mice.
• * To compare the efficacy of different parthenogenetic stimulants under nuclear transfer conditions.
• * To assess the suitability of TRf and ICR mouse strains for oocyte activation studies.

Main Methods:

• * Oocytes were harvested from random-bred TRf and ICR mice.
• * Cumulus-free oocytes were exposed to various parthenogenetic stimulants, focusing on strontium ions and calcium ionophores.
• * Activation rates were quantified and compared between different mouse strains and stimuli.

Main Results:

• * Strontium ion (Sr2+) or calcium ionophore treatment significantly activated a substantial proportion of cumulus-free oocytes from TRf mice.
• * These stimuli demonstrated lower efficacy in activating cumulus-free oocytes from ICR mice.
• * Many previously described stimulants were ineffective for activating cumulus-free oocytes under these conditions.

Conclusions:

• * Strontium ions and calcium ionophores are effective parthenogenetic activators for cumulus-free oocytes in specific random-bred mouse strains (TRf).
• * Oocyte responsiveness to activation stimuli varies between different random-bred mouse strains.
• * These findings have implications for optimizing nuclear transfer protocols and improving cloning efficiency in mice.