The involvement of neurofilament heavy chain phosphorylation in the maturation and degeneration of rat oocytes.
Neurofilaments (NF) are intermediate filament proteins that were originally found to be expressed in neurons and are involved in the maintenance of axonal structure. However, there has not been much research on the expression and physiological significance of NF in other organs. In the present study, we examined the expression of NF in rat ovaries and found that NF heavy chain (NF-H) was expressed in oocytes of follicles from the primary to mature stages, ovulated oocytes, fertilized zygotes, and degenerative oocytes of atretic follicles. Cytoplasmic NF-H disappeared at the two-cell stage of embryonic development, whereas degenerative oocytes of atretic follicles continued to express NF-H even after fragmentation. An antibody that specifically recognizes phosphorylated NF-H (pNF-H) was used to examine the pattern of NF-H phosphorylation in oocytes. pNF-H was detected in the cytoplasm and nuclei of oocytes of mature and atretic follicles, ovulated oocytes, and one-cell zygotes. Treatment with 3,3'-iminodipropionitrile, which induces aberrant phosphorylation of NF in the perikarya of neurons and causes neuropathy, induced oocyte degeneration with follicular atresia, phosphorylation of NF-H in oocytes, and ovarian gene expression of cyclin-dependent kinase 5, a candidate kinase of NF-H. However, an indicator of neuron degeneration, Fluoro-Jade C, failed to stain the pNF-H-immunopositive oocytes. Our results indicate that NF-H expressed in oocytes may be involved in the maintenance of oocyte structure during follicular growth and that the phosphorylation of NF-H in ephemeral oocytes may contribute to the degeneration process of oocytes.
Department of Obstetrics and Gynecology, St. Marianna University School of Medicine, Kawasaki, Kanagawa 216-8511, Japan. n-tkhs@marianna-u.ac.jp
Noriyuki
N
Takahashi
Bunpei
B
Ishizuka
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D023421:Models, Animal; D016900:Neurofilament Proteins / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D009866:Oogenesis / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010053:Ovary / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D016900:Neurofilament Proteins; D009570:Nitriles; C051774:neurofilament protein H; C008110:3,3'-iminodipropionitrile