Developmental analysis of the grandchildless (gs(1)N26) mutation in Drosophila melanogaster: abnormal cleavage patterns and defects in pole cell formation.

This article describes developmental analysis of gs(1)N26 mutation. gs(1)N26 is a temperature-sensitive maternal-effect mutation affecting the formation of the germ line (Y. Niki and M. Okada, Wilhelm Roux's Arch. Dev. Biol. 190, 1-10, 1981). At 25 degrees C, the cleavage nuclei do not divide synchronously and show various degrees of retarded migration to the posterior region. Blastoderm nuclei show antero-posterior mitotic waves; posterior yolk nuclei also are reduced in number at this stage. Pole cells form only when the cleavage nuclei migrate directly to the posterior pole. In fact, the posterior region of young eggs presents the usual ultrastructural features, and it is also able to participate in the formation of pole cells, as was proven by cytoplasmic transfer experiments. Therefore the defects in blastogenesis, in particular in the formation of pole cells of gs(1)N26 embryos, appear to result from the delayed migration of cleavage nuclei to the posterior pole.