<i>Germ cell-less</i> encodes a cell type-specific nuclear pore-associated protein and functions early in the germ-cell specification pathway of <i>Drosophila</i>

The maternally supplied pole plasm at the posterior pole of a Drosophila embryo contains determinants that specify both the germ-cell precursors (pole cells) and the posterior axis. One pole plasm component, the product of the germ cell-less gene, has been found to be required for specification of pole cells, but not posterior somatic cells. Mothers with reduced levels of gc1 give rise to progeny that lack pole cells, but are otherwise normal. Mothers overexpressing gc1, on the other hand, produce progeny exhibiting a transient increase of pole cells. Ectopic localization of gc1 to the anterior pole of the embryo causes nuclei at that location to adopt characteristics of pole cell nuclei, with concurrent loss of somatic cells. We also present evidence indicating that the gc1 protein associates specifically with the nuclear pores of the pole cell nuclei. This localization suggests a novel mechanism in the specification of cell fate for the germ line.