Reduced Expression of MAD2, BCL2, and MAP Kinase Activity in Pig Oocytes after In Vitro Aging Are Associated with Defects in Sister Chromatid Segregation During Meiosis II and Embryo Fragmentation After Activation
This study was conducted to examine expression of centromere protein B (CENPB), spindle checkpoint protein MAD2 (mitotic arrest deficient protein), and antiapoptotic protein BCL2; activities of MAPK (mitogen-activated protein kinase) and mitochondria distribution in pig oocytes during aging, and the...
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Veröffentlicht in: | Biology of reproduction 2005-02, Vol.72 (2), p.373-383 |
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Zusammenfassung: | This study was conducted to examine expression of centromere protein B (CENPB), spindle checkpoint protein MAD2 (mitotic arrest
deficient protein), and antiapoptotic protein BCL2; activities of MAPK (mitogen-activated protein kinase) and mitochondria
distribution in pig oocytes during aging, and their relationship with sister chromatid separation during meiosis II and embryo
fragmentation and apoptosis after activation. After immature oocytes were cultured for 40â72 h, CENPB, MAD2, tubulin, BCL2,
and MAPK in the oocytes were examined by immunoblotting. Spindles, chromosomes, kinetochores, and mitochondria were examined
by immunofluorescence staining and apoptosis was examined by TUNEL assay. It was found that tubulin and CENPB was not changed
during 40â72 h of culture. However, the expression of MAD2 and BCL2 and the activity of MAPK were gradually reduced during
oocyte aging. The percentages of oocytes with normal spindle, chromosomes, and kinetochores were also reduced as oocyte aged
from 9.5% at 40 h to 17.3%, 34.6%, and 42.9% at 48, 60, and 72 h, respectively. Aggregated mitochondria were found in the
aged oocytes as compared with the uniform distribution in young oocytes. After activation, the proportions of oocytes with
abnormal anaphase II were significantly increased in aged oocytes. More ( P < 0.001) oocytes cultured for 60â72 h fragmented and showed apoptosis after activation as compared with the oocytes cultured
for 40â48 h. This study indicates that aging reduces expression in spindle checkpoint protein and antiapoptosis protein and
MAPK activity in pig oocytes. These events in turn cause abnormal sister chromatid segregation during meiosis II, embryo fragmentation,
and apoptosis.
Abstract
Aging reduces expression of spindle checkpoint protein, anti-apoptosis protein, and MAPK activity in pig oocytes |
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ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod.104.030999 |