Akt mediates self-renewal division of mouse spermatogonial stem cells.
Spermatogonial stem cells have unique properties to self-renew and support spermatogenesis throughout their lifespan. Although glial cell line-derived neurotrophic factor (GDNF) has recently been identified as a self-renewal factor for spermatogonial stem cells, the molecular mechanism of spermatogonial stem cell self-renewal remains unclear. In the present study, we assessed the role of the phosphoinositide-3 kinase (PI3K)-Akt pathway using a germline stem (GS) cell culture system that allows in vitro expansion of spermatogonial stem cells. Akt was rapidly phosphorylated when GDNF was added to the GS cell culture, and the addition of a chemical inhibitor of PI3K prevented GS cell self-renewal. Furthermore, conditional activation of the myristoylated form of Akt-Mer (myr-Akt-Mer) by 4-hydroxy-tamoxifen induced logarithmic proliferation of GS cells in the absence of GDNF for at least 5 months. The myr-Akt-Mer GS cells expressed spermatogonial markers and retained androgenetic imprinting patterns. In addition, they supported spermatogenesis and generated offspring following spermatogonial transplantation into the testes of infertile recipient mice, indicating that they are functionally normal. These results demonstrate that activation of the PI3K-Akt pathway plays a central role in the self-renewal division of spermatogonial stem cells.
Lee
Jiyoung
J
Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
Kanatsu-Shinohara
Mito
M
Inoue
Kimiko
K
Ogonuki
Narumi
N
Miki
Hiromi
H
Toyokuni
Shinya
S
Kimura
Tohru
T
Nakano
Toru
T
Ogura
Atsuo
A
Shinohara
Takashi
T
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D005260:Female; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism / Q000502:physiology*; D013093:Spermatogonia / Q000166:cytology* / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D013737:Testis / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D013629:Tamoxifen; C407737:Neurog3 protein, mouse; C016601:afimoxifene