UASp regulatory sequences (from the pWALIUM22 plasmid) drive expression of the cta open reading frame (amplified from the LD04530 cDNA clone), mutated to carry a Q303L amino acid replacement (this results in a constitutively active protein). Sequence consisting of the nanos translational control element (TCE) and the pgc 3'UTR are present downstream of the coding sequence; this targets expression of the protein to the primordial germ cells.