The pluripotency factor LIN28 marks undifferentiated spermatogonia in mouse.
BACKGROUND
Life-long production of spermatozoa depends on spermatogonial stem cells. Spermatogonial stem cells exist among the most primitive population of germ cells - undifferentiated spermatogonia. Transplantation experiments have demonstrated the functional heterogeneity of undifferentiated spermatogonia. Although the undifferentiated spermatogonia can be topographically divided into As (single), Apr (paired), and Aal (aligned) spermatogonia, subdivision of this primitive cell population using cytological markers would greatly facilitate characterization of their functions.


RESULTS
In the present study, we show that LIN28, a pluripotency factor, is specifically expressed in undifferentiated spermatogonia (As, Apr, and Aal) in mouse. Ngn3 also specifically labels undifferentiated spermatogonia. We used Ngn3-GFP knockin mice, in which GFP expression is under the control of all Ngn3 transcription regulatory elements. Remarkably, Ngn3-GFP is only expressed in approximately 40% of LIN28-positive As (single) cells. The percentage of Ngn3-GFP-positive clusters increases dramatically with the chain length of interconnected spermatogonia.


CONCLUSIONS
Our study demonstrates that LIN28 specifically marks undifferentiated spermatogonia in mice. These data, together with previous studies, suggest that the LIN28-expressing undifferentiated spermatogonia exist as two subpopulations: Ngn3-GFP-negative (high stem cell potential) and Ngn3-GFP-positive (high differentiation commitment). Furthermore, Ngn3-GFP-negative cells are found in chains of Ngn3-GFP-positive spermatogonia, suggesting that cells in the Aal spermatogonia could revert to a more primitive state.
Zheng
Ke
K
Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA 19104, USA. kezheng@vet.upenn.edu
Wu
Xin
X
Kaestner
Klaus H
KH
Wang
Peijing Jeremy
PJ
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013093:Spermatogonia / Q000166:cytology* / Q000378:metabolism*; D014162:Transfection
D051792:Basic Helix-Loop-Helix Proteins; D049452:Green Fluorescent Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C488352:Lin-28 protein, mouse; C407737:Neurog3 protein, mouse