Similar morphological and molecular signatures shared by female and male germline stem cells

The existence of mammalian female germline stem cells (FGSCs) indicates that mammalian ovaries possess germline stem cells analogous to testis, and continue to produce gametes postnatally, which provides new insights into female fertility. In this study, we compared the morphological and molecular characteristics between FGSCs and spermatogonial stem cells (SSCs) by analysis of morphology, immunofluorescence, alkaline phosphatase activity assay, reverse transcription polymerase chain reaction (RT-PCR) and microarray hybridization. The results demonstrated that the morphology and growth patterns of FGSCs are similar to those of SSCs. Microarray analysis of global gene expression profiles of FGSCs and SSCs showed similar signatures in the transcriptome level. A list of 853 co-highly expressed genes (CEG) in female and male germline stem cells may be responsible for the morphological and molecular similarity. We constructed a continuous network of the CEG based on I2D protein-protein interaction database by breadth first search. From the network, we could observe the interactions of the CEG may be responsible for maintaining the properties of germline stem cells. This study was the first attempt to compare morphological and molecular characteristics between FGSCs and SSCs. These findings would provide some clues for further research on mammalian FGSCs.