Calcium-binding proteins and calcium-release channels in human maturing oocytes, pronuclear zygotes and early preimplantation embryos.
BACKGROUND
The study aim was to investigate the presence and localization of Ca2+-binding proteins and Ca2+-release receptor channels in human maturing oocytes, pronuclear zygotes and preimplantation embryos.


METHODS
Immunocytochemical analysis, using specific antibodies against the proteins being studied, followed with confocal laser microscopy, was performed on human oocytes and embryos.


RESULTS
Calreticulin and calsequestrin (the two major calcium storage proteins of somatic cells), two types of calcium release receptors, the inositol trisphosphate and ryanodine receptors (InsP(3)R-2, RyRs-1,2,3), and the molecular chaperone, calnexin, were identified in all investigated cell types. Calreticulin was predominant in the cell cortex and in the nuclear envelope, while calsequestrin was distributed throughout the entire cytoplasm. Generally, localization of the InsP(3)R-2 and RyRs was similar to that of calreticulin and calsequestrin respectively. Both types of receptor were enriched in the subplasmalemmal region of meiotic oocytes. In addition, the InsP(3)R was detected in the nuclear structures of oocytes and blastomeres. Calnexin distribution overlapped with that of calreticulin but appeared to be present in distinct subcompartments.


CONCLUSIONS
Human oocytes and embryos express the calcium sequestration and release proteins in highly organized and developmentally regulated patterns. Fine-tuning of these proteins may play a crucial role in regulation of Ca2+ transience during oocyte maturation, fertilization and early embryo development.
Balakier
Hanna
H
CReATe (Canadian Reproductive Assisted Technology) Program Inc, Toronto, Ontario, Canada. hbalakier@sympatico.ca
Dziak
Ewa
E
Sojecki
Agata
A
Librach
Clifford
C
Michalak
Marek
M
Opas
Michal
M
D001755:Blastocyst / Q000166:cytology / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D037282:Calreticulin / Q000378:metabolism; D002155:Calsequestrin / Q000378:metabolism; D016922:Cellular Senescence; D006801:Humans; D007150:Immunohistochemistry; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018613:Microscopy, Confocal; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D014018:Tissue Distribution; D015053:Zygote / Q000378:metabolism*
D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D002155:Calsequestrin; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel