Many types of cells are able to make their way through the body propelled by molecular motors and guided by pathfinding mechanisms. One of the great migratory phenomena in development is the journey undertaken by primordial germ cells in the Drosophila embryo. These cells form externally to the embryo at its posterior pole, are carried within by a process of invagination and navigate unerringly through the body to contribute to the formation of the gonad, acquiring the characteristics of more mature germ cells en route. The puzzle of how these cells find their way through the developing body has challenged biologists for years, but is now beginning to yield to their painstaking efforts toward identifying the underlying mechanisms that guide these travelers on their way.

Kazuko Hanyu-Nakamura and colleagues in the RIKEN Center for Developmental Biology Laboratory for Germline Development (Akira Nakamura, Team Leader; Kobe, Japan) have fit a new piece into this jigsaw with findings recently published in the online edition of Development , describing an intriguing new model of germ cell migration involving a pair of guidance molecules, Wunen and Wunen2, and their discrete activities in germ and somatic cells.

The study began with a screen for mutant flies, which uncovered a phenotype in which the flies' primordial germ cells, called "pole cells," showed defects during their migration: the pole cells died in large numbers at a stage when they would normally begin to associate with the gonadal mesoderm. The genetic deficiency responsible for the defect was identified as a maternal effect mutation, meaning that its function (or loss of function) relies entirely on transmission by the mother fly. A closer analysis of the failing pole cells indicated that they began their development and migration normally, and that their deaths did not display a significant increase in the molecular activity most commonly associated with programmed cell death activation of
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Contact: Doug Sipp
sipp@cdb.riken.jp
RIKEN Center for Developmental Biology
9-Sep-2004

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