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Comment |
Balakier H, et al 2002 reported the expression of calcium-binding proteins and calcium-release channels in human
maturing oocytes, pronuclear zygotes and early preimplantation
embryos.
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.
Immunocytochemical analysis, using specific antibodies against the proteins
being studied, followed with confocal laser microscopy, was performed on human
oocytes and embryos. 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.
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