Although it has been known for over a century that sea urchin eggs are polarized cells, very little is known about the mechanism responsible for establishing and maintaining polarity. Our previous studies of microtubule organization during sea urchin oogenesis described a cortical microtubule-organizing center (MTOC) present during germinal vesicle (GV) migration in large oocytes. This MTOC was...

The Drosophila melanogaster gurken gene encodes a TGF alpha-like signaling molecule that is secreted from the oocyte during two distinct stages of oogenesis to define the coordinate axes of the follicle cell epithelium that surrounds the oocyte and its 15 anterior nurse cells. Because the gurken receptor is expressed throughout the epithelium, axial patterning requires region-specific secretion...

ly ovarioles spit out oocyte-containing cysts “like a sausage machine,” says Daniel St. Johnston. In the process, the cysts are endowed with a clearly defined anterior-posterior polarity axis based on the posterior positioning of the oocyte. “The [axis] is hardwired into the geometry of the ovary,” says St. Johnston. “What we’re describing is the mechanism that transmits this.” That mechanism i...

ly ovarioles spit out oocyte-containing cysts “like a sausage machine,” says Daniel St. Johnston. In the process, the cysts are endowed with a clearly defined anterior-posterior polarity axis based on the posterior positioning of the oocyte. “The [axis] is hardwired into the geometry of the ovary,” says St. Johnston. “What we’re describing is the mechanism that transmits this.” That mechanism i...

Here we describe our analyses of Rhino, a novel member of the Heterochromatin Protein 1(HP1) subfamily of chromo box proteins. rhino (rhi) is expressed only in females and chiefly in the germline, thus providing a new tool to dissect the role of chromo-domain proteins in development. Mutations in rhi disrupt eggshell and embryonic patterning and arrest nurse cell nuclei during a stage-specific ...

We have characterized the function of a new neurogenic locus, brainiac (brn), during oogenesis. Homozygous brn females lay eggs with fused dorsal appendages, a phenotype associated with torpedo (top) alleles of the Drosophila EGF receptor (DER) locus. By constructing double mutant females for both brn and top, we have found that brn is required for determining the dorsal-ventral polarity of the...

The localization of specific mRNAs can establish local protein gradients that generate and control the development of cellular asymmetries. While all evidence underscores the importance of the cytoskeleton in the transport and localization of RNAs, we have limited knowledge of how these events are regulated. Using a visual screen for motile proteins in a collection of GFP protein trap lines, we...

Polarization of the anteroposterior (AP) axis of the Drosophila oocyte occurs early in oogenesis, while the presumptive oocyte is still in the germarium (Gonzalez-Reyes and St Johnston, 1998). The dorsoventral (DV) axis is set up much later and relies on transfer of the AP axis polarity from the oocyte to the somatic follicle cells at the posterior end of the oocyte. During stages 4-6 in wild-t...