Oocyte activation and Ca2+ oscillation-inducing abilities of mouse round/elongated spermatids and the developmental capacities of embryos from spermatid injection
H. Yazawa et al., Oocyte activation and Ca2+ oscillation-inducing abilities of mouse round/elongated spermatids and the developmental capacities of embryos from spermatid injection, HUM REPR, 16(6), 2001, pp. 1221-1228
To investigate differences in fertilization mechanisms and the potential cl
inical use of round/elongated spermatid, rye conducted detailed studies of
oocyte activation and Ca2+ oscillation-inducing abilities in these immature
sperm cells and compared these abilities against those of mature spermatoz
oa, When round spermatids from B6D2F1 mice were injected, none of the oocyt
es was activated and no intracellular Ca2+ ([Ca2+](i)) increases were obser
ved. Elongated spermatids could induce activation normally in 87% of inject
ed oocytes, but Ca2+ oscillation could not be induced at all and most of th
e oocytes (94%) exhibited only several transient [Ca2+](i) rises (transient
patterns). Because normal offspring could be obtained when embryos through
elongated spermatid injection were transferred to foster mothers, it seems
that a normal oscillation pattern of [Ca2+](i) is not essential for normal
fertilization and embryo development. [Ca2+](i) patterns of injected oocyt
es changed from transient patterns to oscillation patterns while the inject
ed immature sperm cells were maturing to spermatozoa, Dissociations were se
en between the timing of appearance of oocyte activation and that of Ca2+ o
scillation-inducing abilities in maturing sperm cells. These dissociations
may be due to differences in the thresholds to oocyte activation and Ca2+ o
scillation-inducing factor for inducing oocyte activation and Ca2+ oscillat
ion.