
<ArticleTitle>A nuclear <prot>lamin</prot> is required for cytoplasmic organization and egg polarity in Drosophila.</ArticleTitle>
<AbstractText>Nuclear <prot>lamin</prot>s are intermediate filaments that compose the nuclear lamina--the filamentous meshwork underlying the inner nuclear membrane--and are required for nuclear assembly, organization and maintenance. Here we present evidence that a nuclear <prot>lamin</prot> is also required for cytoplasmic organization in two highly polarized cell types. Zygotic loss-of-function mutations in the Drosophila gene encoding the principal <prot>lamin</prot> (<prot>Dm(0)</prot>) disrupt the directed outgrowth of cytoplasmic extensions from terminal cells of the tracheal system. Germline mutant clones disrupt dorsal-ventral polarity of the oocyte. In mutant oocytes, transcripts of the dorsal determinant Gurken, a transforming growth factor-alpha homologue, fail to localize properly around the anterodorsal surface of the oocyte nucleus; their ventral spread results in dorsalized eggs that resemble those of the classical dorsalizing mutations squid and fs(1)K10. The requirement of a nuclear <prot>lamin</prot> for cytoplasmic as well as nuclear organization has important implications for both the cellular functions of <prot>lamin</prot>s and the pathogenesis of human diseases caused by <prot>lamin</prot> mutations.</AbstractText>
