Injection of a Sperm Extract Triggers Egg Activation in the Newt Cynops pyrrhogaster

Unfertilized eggs of the newt Cynops pyrrhogaster are arrested at the second meiotic metaphase. The primary signal for egg activation is a transient increase in [Ca2+]i, which is triggered by the fertilizing sperm and propagates over the egg cortex as a Ca2+ wave. We injected an extract of Cynops sp...

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Bibliographic Details
Published in:Developmental biology 2001-02, Vol.230 (1), p.89-99
Main Authors: Yamamoto, Satoshi, Kubota, Hiroshi Y., Yoshimoto, Yasuaki, Iwao, Yasuhiro
Format: Article
Language:English
Subjects:
amphibian
Animals
Bromodeoxyuridine - metabolism
Ca2
Calcium Channels - metabolism
Calcium Signaling
Chelating Agents - pharmacology
Cyclin B - metabolism
Cyclin B1
Cynops pyrrhogaster
DNA Replication
egg activation
Egtazic Acid - analogs & derivatives
Egtazic Acid - pharmacology
Female
In Vitro Techniques
Inositol 1,4,5-Trisphosphate Receptors
IP3
Male
Ovum - drug effects
Ovum - physiology
Ovum - ultrastructure
Receptors, Cytoplasmic and Nuclear - metabolism
Salamandridae - physiology
sperm extract
Sperm-Ovum Interactions - drug effects
Sperm-Ovum Interactions - physiology
Spermatozoa - physiology
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Summary:Unfertilized eggs of the newt Cynops pyrrhogaster are arrested at the second meiotic metaphase. The primary signal for egg activation is a transient increase in [Ca2+]i, which is triggered by the fertilizing sperm and propagates over the egg cortex as a Ca2+ wave. We injected an extract of Cynops sperm (SE) into unfertilized eggs and induced a wave-like [Ca2+]i increase which resulted in activation and resumption of meiosis. The SE-injected eggs showed degradation of cyclin B1 and DNA replication. When SE was boiled or treated with proteinase K before injection, it was unable to cause egg activation. Preinjection of Ca2+-chelator BAPTA before SE injection inhibited egg activation. These results indicate that a heat-labile and proteinaceous factor in the sperm cytoplasm induces a transient increase in [Ca2+]i which is required for egg activation. Injection of IP3 into unfertilized eggs caused an increase in [Ca2+]i and egg activation, but injection of cADP-ribose did not. These results support the hypothesis that Ca2+ release at fertilization occurs via IP3 receptors.
ISSN:0012-1606
1095-564X
DOI:10.1006/dbio.2000.9949