Multipotent adult germline stem cells and embryonic stem cells: comparative proteomic approach.

Spermatogonial stem cells isolated from the adult mouse testis acquire under certain culture conditions pluripotency and become so-called multipotent adult germline stem cells (maGSCs). They can be differentiated into somatic cells of the three germ layers. We investigated a subset of the maGSCs and ESCs proteomes using cell lines derived from two different mouse strains, narrow range immobilized pH gradients to favor the detection of less abundant proteins, and DIGE to ensure confident comparison between the two cell types. 2-D reference maps of maGSCs and ESCs in the pI ranges 3-6 and 5-8 were created, and protein entities were further processed for protein identification. By peptide mass fingerprinting and tandem mass spectrometry combined with searches of protein sequence databases, a set of 409 proteins was identified, corresponding to a library of 166 nonredundant stem cell-associated proteins. The identified proteins were classified according to their main known/postulated functions using bioinformatics. Furthermore, we used DIGE to highlight the ESC-like nature of maGSCs on the proteome scale. We concluded that the proteome of maGSCs is highly similar to that of ESCs as we could identify only a small subset of 18 proteins to be differentially expressed between the two cell types. Moreover, comparative analysis of the cell line proteomes from two different mouse strains showed that the interindividual differences in maGSCs proteomes are minimal. With our study, we created for the first time a proteomic map for maGSCs and compared it to the ESCs proteome from the same mouse. We confirmed on the proteome level the ESC-like nature of maGSCs.