Cytostatic factor proteins are present in male meiotic cells and beta-nerve growth factor increases mos levels in rat late spermatocytes.
BACKGROUND
In co-cultures of pachytene spermatocytes with Sertoli cells, beta-NGF regulates the second meiotic division by blocking secondary spermatocytes in metaphase (metaphase II), and thereby lowers round spermatid formation. In vertebrates, mature oocytes are arrested at metaphase II until fertilization, because of the presence of cytostatic factor (CSF) in their cytoplasm. By analogy, we hypothesized the presence of CSF in male germ cells.


RESULTS
We show here, that Mos, Emi2, cyclin E and Cdk2, the four proteins of CSF, and their respective mRNAs, are present in male rat meiotic cells; this was assessed by using Western blotting, immunocytochemistry and reverse transcriptase PCR. We measured the relative cellular levels of Mos, Emi2, Cyclin E and Cdk2 in the meiotic cells by flow cytometry and found that the four proteins increased throughout the first meiotic prophase, reaching their highest levels in middle to late pachytene spermatocytes, then decreased following the meiotic divisions. In co-cultures of pachytene spermatocytes with Sertoli cells, beta-NGF increased the number of metaphases II, while enhancing Mos and Emi2 levels in middle to late pachytene spermatocytes, pachytene spermatocytes in division and secondary spermatocytes.


CONCLUSIONS
Our results suggest that CSF is not restricted to the oocyte. In addition, they reinforce the view that NGF, by enhancing Mos in late spermatocytes, is one of the intra-testicular factors which adjusts the number of round spermatids that can be supported by Sertoli cells.
Institut de génomique fonctionnelle de Lyon, Université de Lyon, INRA UMR 1288, CNRS UMR 5242, Université Lyon 1, Ecole Normale Supérieure de Lyon, Lyon, France. marie-helene.durand@ens-lyon.fr
Marie-Hélène
MH
Perrard
Emeric
E
Chassaing
Guillaume
G
Montillet
Odile
O
Sabido
Philippe
P
Durand
D000818:Animals; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D044783:F-Box Proteins / Q000378:metabolism; D008297:Male; D008540:Meiosis; D020932:Nerve Growth Factor / Q000378:metabolism*; D017231:Proto-Oncogene Proteins c-mos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012708:Sertoli Cells / Q000378:metabolism*; D013087:Spermatids / Q000378:metabolism*; D013090:Spermatocytes / Q000378:metabolism*
D019927:Cyclin E; C546111:Emi2 protein, rat; D044783:F-Box Proteins; D020932:Nerve Growth Factor; D017231:Proto-Oncogene Proteins c-mos; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2