Abstract
BackgroundPrimordial germ cell (PGC) specification is the first crucial step in germ line development. However, owing to significant challenges regarding the in vivo system, such as the complex cellular environment and potential problems with embryo manipulation, it is desirable to generate embryonic stem (ES) cells that are capable of overcoming these aforementioned limitations in order to provide a potential in vitro model to recapitulate the developmental processes in vivo.Methodology and Principal FindingsHere, we studied the detailed process of PGC specification from stella-GFP ES cells. We first observed the heterogeneous expression of stella in ES cells. However, neither Stella-positive ES cells nor Stella-negative ES cells shared a similar gene expression pattern with either PGCs or PGC precursors. Second, we derived PGCs from ES cells using two differentiation methods, namely the attachment culture technique and the embryoid body (EB) method. Compared with PGCs derived via the attachment culture technique, PGCs derived via the EB method that had undergone the sequential erasure of Peg3 followed by Igf2r resulted in a cell line in which the expression dynamics of T, Fgf8 and Sox17, in addition to the expression of the epiblast markers, were more similar to the in vivo expression, thus demonstrating that the process of PGC derivation was more faithfully recapitulated using the EB method. Furthermore, we developed an in vitro model of PGC specification in a completely chemically defined medium (CDM) that indicated that BMP4 and Wnt3a promoted PGC derivation, whereas BMP8b and activinA had no observable effect on PGC derivation.Conclusions and SignificanceThe in vitro model we have established can recapitulate the developmental processes in vivo and provides new insights into the mechanism of PGC specification.
Highlights
The investigation of primordial germ cell (PGC) specification is the first essential step in the process of elucidating the mechanisms involved in the development of a germ cell lineage
The in vitro model we have established can recapitulate the developmental processes in vivo and provides new insights into the mechanism of Primordial germ cell (PGC) specification
The genes expressed in different stages of the PGC precursors and PGCs prior to E8.25 are summarized in Table 1 [17]
Summary
The investigation of primordial germ cell (PGC) specification is the first essential step in the process of elucidating the mechanisms involved in the development of a germ cell lineage. Significant difficulties exist with regard to research into the process of PGC specification in vivo. Embryonic stem (ES) cells, which have overcome these aforementioned difficulties, provide promising candidates to recapitulate the developmental process in vitro and serve as a model to complement studies in vivo. Owing to significant challenges regarding the in vivo system, such as the complex cellular environment and potential problems with embryo manipulation, it is desirable to generate embryonic stem (ES) cells that are capable of overcoming these aforementioned limitations in order to provide a potential in vitro model to recapitulate the developmental processes in vivo
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