Control over the morphology and segregation of Zebrafish germ cell granules during embryonic development.
BACKGROUND
Zebrafish germ cells contain granular-like structures, organized around the cell nucleus. These structures share common features with polar granules in Drosophila, germinal granules in Xenopus and chromatoid bodies in mice germ cells, such as the localization of the zebrafish Vasa, Piwi and Nanos proteins, among others. Little is known about the structure of these granules as well as their segregation in mitosis during early germ-cell development.


RESULTS
Using transgenic fish expressing a fluorescently labeled novel component of Zebrafish germ cell granules termed Granulito, we followed the morphology and distribution of the granules. We show that whereas these granules initially exhibit a wide size variation, by the end of the first day of development they become a homogeneous population of medium size granules. We investigated this resizing event and demonstrated the role of microtubules and the minus-end microtubule dependent motor protein Dynein in the process. Last, we show that the function of the germ cell granule resident protein the Tudor domain containing protein-7 (Tdrd7) is required for determination of granule morphology and number.


CONCLUSIONS
Our results suggest that Zebrafish germ cell granules undergo a transformation process, which involves germ cell specific proteins as well as the microtubular network.
Germ Cell Development, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany. mjs@gmx.ch
Markus J
MJ
Strasser
Natalia C
NC
Mackenzie
Karin
K
Dumstrei
La-Iad
LI
Nakkrasae
Jürg
J
Stebler
Erez
E
Raz
D000818:Animals; D030801:Animals, Genetically Modified; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D053487:DEAD-box RNA Helicases / Q000235:genetics; D004398:Dyneins / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000196:embryology; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers; D005854:Germ Cells / Q000648:ultrastructure*; D049452:Green Fluorescent Proteins; D017403:In Situ Hybridization; D008870:Microtubules / Q000648:ultrastructure; D015027:Zebrafish / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins / Q000235:genetics
D005819:Genetic Markers; D029961:Zebrafish Proteins; D049452:Green Fluorescent Proteins; C498289:ddx4 protein, zebrafish; D053487:DEAD-box RNA Helicases; D004398:Dyneins