Je. Faure et al., The frequency of calcium oscillations in mouse eggs at fertilization is modulated by the number of fused sperm, DEVELOP BIO, 213(2), 1999, pp. 370-377
In a variety of calcium signaling systems, the frequency of intracellular c
alcium oscillations is physiologically important. Probably multiple factors
control the frequency of calcium oscillations in the egg after fertilizati
on and many of these remain to be identified. In this study, we present the
first rigorous set of data showing that monospermic fertilization is impor
tant for setting the physiological calcium oscillation frequency. Recording
s in 152 zona-free eggs show that the general pattern of the calcium oscill
ations is identical in monospermic and polyspermic eggs; however, the oscil
lation frequency is higher in polyspermic eggs (P < 10(-6)). The frequency
of the late oscillations increases with the number of sperm heads incorpora
ted: 5.2 +/- 0.3 spikes per hour (mean +/- SEM; n = 55) in monospermic eggs
, 6.6 +/- 0.3 (n = 62) in dispermic eggs, 8.7 +/- 0.7 (n = 23) in trispermi
c eggs, and 8.9 +/- 0.9 (n = 12) in eggs with four or more sperm heads. The
frequency of the early oscillations is also increased in polyspermic. eggs
. Seventy-eight additional eggs were divided into two groups and inseminate
d with two different sperm concentrations ("low" and "high") to obtain one
group mainly monospermic and the other mainly polyspermic. The two groups o
f eggs oscillated at different frequencies (P < 10(-5)) These data rule out
the possibility of an egg effect in which some eggs would have the dual pr
operties of oscillating faster and of being able to fuse with several sperm
cells. These data instead suggest that the sperm modulates the frequency o
f the oscillations in a dose-dependent manner. (C) 1993 Academic Press.