GERM CELL-LESS ENCODES A CELL-TYPE-SPECIFIC NUCLEAR PORE-ASSOCIATED PROTEIN AND FUNCTIONS EARLY IN THE GERM-CELL SPECIFICATION PATHWAY OF DROSOPHILA

The maternally supplied pole plasm at the posterior pole of a Drosophi la embryo contains determinants that specify both the germ-cell precur sors (pole cells) and the posterior axis. One pole plasm component, th e product of the germ cell-less gene, has been found to be required fo r specification of pole cells, but not posterior somatic cells. Mother s with reduced levels of gcl give rise to progeny that lack pole cells , but are otherwise normal. Mothers overexpressing gcl, on the other h and, produce progeny exhibiting a transient increase of pole cells. Ec topic localization of gcl to the anterior pole of the embryo causes nu clei at that location to adapt characteristics of pole cell nuclei, wi th concurrent loss of somatic cells. We also present evidence indicati ng that the gcl 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.