Mol. Hum. Reprod. Advance Access published online on February 27, 2007
Molecular Human Reproduction, doi:10.1093/molehr/gal121
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Comparison of Ca2+ and CaMKII responses in IVF and ICSI in the mouse
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1 Sackler School of Biomedical Sciences, Program in Cell, Molecular, and Developmental Biology, Tufts University School of Medicine, Boston, MA, USA 2 Department of Veterinary and Animal Sciences, University of MA, Amherst, MA, USA 3 Department of Obstetrics and Gynecology, Tufts-New England Medical Center, Boston, MA, USA
4 To whom Correspondence should be addressed at: Department of Obstetrics and Gynecology, Box 36, Tufts-New England Medical Center, 750 Washington St., Boston, MA 02111, USA. E-mail: tducibella{at}tufts-nemc.org
Novel methods of egg activation in human assisted reproductive technologies and animal somatic cell nuclear transfer are likely to alter the signalling process that occurs during normal fertilization. Intracytoplasmic sperm injection (ICSI) bypasses the normal processes of the acrosome reaction, sperm–egg fusion, and processing of the sperm plasma membrane, as well as alters some parameters of intracellular calcium ([Ca2+]i) dynamics (reported previously by Kurokawa and Fissore (2003)). Herein, we extend these studies to determine if ICSI alters the activity of the Ca2+-dependent protein, Ca2+/calmodulin-dependent kinase II (CaMKII), which is responsible for the completion of meiosis in vertebrate eggs. After ICSI or in vitro fertilization (IVF), individual mouse eggs were monitored for their relative changes in both [Ca2+]i and CaMKII activity during the first [Ca2+]i rise and a subsequent rise associated with second polar body extrusion. The duration of the first [Ca2+]i rise was greater in ICSI than in IVF, but the amplitude of the rise was transiently higher for IVF than ICSI. However, a similar mean CaMKII activity was observed in both procedures. During polar body extrusion, the amplitude and duration of the Ca2+ rises were increased by a small amount in ICSI compared with IVF, whereas the CaMKII activities were similar. Thus, compared with IVF, ICSI is not associated with decreased or delayed CaMKII activity in response to these Ca2+ signals in the mouse.
Key Words: calcium/CaMKII/fertilization/ICSI/IVF
These authors contributed equally to this work.
Current address: Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
¶ Current address: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
Submitted on December 14, 2006; accepted on January 5, 2007.