Egg activation events are regulated by the duration of a sustained [Ca super(2+)] sub(cyt) signal in the mouse

• Published in: Developmental biology 2005-06, Vol.282 (1), p.39-54
• Main Authors: Ozil, J-P, Markoulaki, S, Toth, S, Matson, S, Banrezes, B, Knott, J G, Schultz, R M, Huneau, D, Ducibella, T
• Format: Article
• Language: English
• ISSN: 0012-1606
• DOI: 10.1016/j.ydbio.2005.02.035

Although the dynamics of oscillations of cytosolic Ca super(2+) concentration ([Ca super(2+)] sub(cyt)) play important roles in early mammalian development, the impact of the duration when [Ca super(2+)] sub(cyt) is elevated is not known. To determine the sensitivity of fertilization-associated responses [i.e. cortical granule exocytosis, resumption of the cell cycle, Ca super(2+)/calmodulin-dependent protein kinase II (CaMKII) activity, recruitment of maternal mRNAs] and developmental competence of the parthenotes to the duration of a [Ca super(2+)] sub(cyt) transient, unfertilized mouse eggs were subjected to a prolonged [Ca super(2+)] sub(cyt) change for 15, 25, or 50 min by means of repetitive Ca super(2+) electropermeabilization at 2-min intervals. The initiation and completion of fertilization-associated responses are correlated with the duration of time in which the [Ca super(2+)] sub(cyt) is elevated, with the exception that autonomous CaMKII activity is down-regulated with prolonged elevated [Ca super(2+)] sub(cyt). Activated eggs from 25-or 50-min treatments readily develop to the blastocyst stage with no sign of apoptosis or necrosis and some implant. Ca super(2+) influx into unfertilized eggs causes neither Ca super(2+) release from intracellular stores nor rapid removal of cytosolic Ca super(2+). Thus, the total Ca super(2+) signal input appears to be an important regulatory parameter that ensures completion of fertilization-associated events and oocytes have a surprising degree of tolerance for a prolonged change in [Ca super(2+)] sub(cyt).