FUNCTIONAL REQUIREMENT OF GP130-MEDIATED SIGNALING FOR GROWTH AND SURVIVAL OF MOUSE PRIMORDIAL GERM-CELLS IN-VITRO AND DERIVATION OF EMBRYONIC GERM (EG) CELLS

Leukemia inhibitory factor (LIF) is a cytokine known to influence prol iferation and/or survival of mouse primordial germ cells (PGC) in cult ure, The receptor complex for LIF comprises LIF-binding subunit and no n-binding signal transducer, gp130, The gp130 was originally identifie d as a signal-transducing subunit of interleukin (IL)-6 and later also found to be a functional component of receptor complexes for other LI F-related cytokines (oncostatin M [OSM], ciliary neurotrophic factor [ CNTF] and IL-11), In this study, we have analyzed the functional role of gp130-mediated signaling in PGC growth in vitro, OSM was able to fu lly substitute for LIF; both cytokines promoted the proliferation of m igratory PGC (mPGC) and enhanced the viability of postmigratory (colon izing) PGC (cPGC) when cultured on SI/S4(4)-m220 cells, Interestingly, IL-11 stimulated mPGC growth comparable to LIF and OSM, but did not a ffect cPGC survival, IL-6 and CNTF did not affect PGC. In addition, a combination of IL-6 and soluble IL-6 binding subunit (sIL-6R), which i s known to activate intracellular signaling via gp130, fully reproduce d the LIF action on PGC, Both in the presence and absence of LIF, addi tion of neutralizing antibody against gp130 in culture remarkably bloc ked cPGC survival, These results suggest a pivotal role of gp130 in PG C development, especially that it is indispensable for cPGC survival a s comparable to the c-KIT-mediated action, We have further demonstrate d that a combination of LIF with forskolin or retinoic acid, a potent mitogen for PGC, supported the proliferation of PGC, leading to propag ation of the embryonic stem cell-like cells, termed embryonic germ (EG ) cells, Since EG cells were also obtained by using OSM or the IL-6/sI L-6R complex in place of LIF, a significant contribution of gp130-medi ated signaling in EG cell formation was further suggested.