A ClustalW alignment of D. melanogaster, A. gambiae (mosquito) and H. sapiens (human) Maelstrom homologs, which are 459, 420 and 434 residues in length, respectively. Identical residues (36 in total, or 7.29%) shared between the proteins are indicated in red and with asterisks; strongly similar (75 in total, or 15.18%) residues are indicated in green and with colons; and weakly similar residues (53 in total, or 10.73%) are indicated in blue type and with periods. Black lines over the Drosophila and human homologs indicate HMG-box-homologous regions.

(A) Distribution of Maelstrom protein during oogenesis. (A) Three-dimensional projection of a confocal z-series stack showing a wild-type ovariole labeled for Maelstrom protein (indirect immunofluorescence inverted, signal is black). Within the germline, Maelstrom is present in all cell types and localizes to highly abundant perinuclear particles in cells of mitotically active region I (red bar), including stem cells (red arrow), in nurse cells (orange arrow) and in the early oocyte (lavender arrow). Maelstrom is also present at low levels within cells of the soma (black arrow). (A, inset) Sixteen-cell germline cysts are generated in region I of the germarium. Here, a germline stem cell undergoes an asymmetric division, renewing itself and producing a cystoblast. The cystoblast then undergoes four mitotic divisions with incomplete cytokinesis to produce a 16-cell germline cyst in which all cells are connected through intercellular bridges, called ring canals. As the cyst exits the germarium, it is ensheathed by a monolayer of somatic follicle cells to form the egg chamber. While still in the germarium, one cell in each cyst is determined to be the oocyte, while the remaining 15 cells become nurse cells. (B) Between stages 9 and 10 (anterior stage 10B egg chamber shown), Maelstrom becomes relatively more concentrated in the nucleoplasm of nurse cells, while perduring in nuage and nurse cell cytoplasm. (Left) Vasa (yellow channel) and Maelstrom (blue channel), overlap is white. (Middle) Maelstrom channel alone. (Right) Vasa channel alone.