OCT-4 - MORE THAN JUST A POUERFUL MARKER OF THE MAMMALIAN GERMLINE

Mammals lack visible cytoplasmic components in the oocyte that could a ccount for 'germline determinants' as identified in various non-mammal ian species. Actually, mammals might not define the germline autonomou sly by localized 'germline determinants' but conditionally depending o n the position of cells within the embryo. The Oct-4 gene encodes a tr anscription factor that is specifically expressed in the toti- and plu ripotential stem cells of the mouse embryo and so far has only been fo und in mammalian species. Oct-4-expressing embryonal cells retain the capacity to differentiate along multiple lineages and they have been s uggested to be part of a 'totipotent germline cycle' that links one ge neration to the next.