PAR-3 defines a central subdomain of the cortical actin cap in mouse eggs.
The evolutionarily conserved partitioning defective (PAR) protein PAR-3 is pivotal for establishing and maintaining cell polarity. During mammalian oocyte maturation, the radially symmetric oocyte is transformed into a highly polarized metaphase II (MII)-arrested egg. We therefore examined several aspects of PAR-3 expression during oocyte maturation. We cloned two novel PAR-3 transcripts from an oocyte library that likely encode proteins of Mr = 73 K and 133 K that are phosphorylated during maturation. PAR-3, which is found throughout the GV-intact oocyte, becomes asymmetrically localized during meiosis. Following germinal vesicle breakdown, PAR-3 surrounds the condensing chromosomes and associates with the meiotic spindles. Prior to emission of the first and second polar bodies, PAR-3 is located within a central subdomain of the polarized actin cap, which overlies the spindle. This cortical PAR-3 localization depends on intact microfilaments. These results suggest a role for PAR-3 in establishing asymmetry in the egg and in defining the future site of polar body emission.
Duncan
Francesca E
FE
Center for Research on Reproduction and Women's Health and Department of Obstetrics and Gynecology, Philadelphia, PA 19104, USA.
Moss
Stuart B
SB
Schultz
Richard M
RM
Williams
Carmen J
CJ
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D016764:Cell Polarity; D003599:Cytoskeleton / Q000378:metabolism; D005260:Female; D007527:Isoenzymes / Q000378:metabolism; D008540:Meiosis / Q000502:physiology; D051379:Mice; D008870:Microtubules / Q000378:metabolism; D009865:Oocytes / Q000166:cytology* / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D007527:Isoenzymes; C115084:Pard3 protein, mouse; D020033:Protein Isoforms; D011493:Protein Kinase C