Cloning and developmental expression of Sna, a murine homologue of the Drosophila snail gene.

The genetic analysis of dorsoventral patterning in Drosophila has identified a zinc-finger gene, snail, that is required for mesoderm formation. The cloning and nuclease protection analysis of a Xenopus homologue of this gene has suggested a possible role in the mesoderm of vertebrates. Here, we describe the cloning of a murine homologue of snail, Sna, and in situ hybridisation studies of its developmental expression. Sequence analysis reveals substantial conservation of the second to fifth zinc fingers, but not of the first zinc finger in the Sna gene. Expression occurs in the ectoplacental cone, parietal endoderm, embryonic and extraembryonic mesoderm, in neural crest and in condensing precartilage. Based on the timing and spatial restriction of expression in embryonic mesoderm, we suggest that Sna might be required for the early development of this tissue, as is the case for its Drosophila counterpart. In addition, we propose that Sna might have an analogous role in the development of neural crest. The expression in condensing precartilage indicates that this gene also has a later function in chondrogenesis.     

Identification and characterization of a novel Drosophila melanogaster glutathione S-transferase-containing FLYWCH zinc finger protein

Glutathione SH-transferase (GST) is a 25-kDa protein and a member of a large family that plays a critical role in the cellular homeostasis of all organisms. In this report, we describe a novel GST-containing protein identified and cloned from Drosophila. This 1045 amino acid protein possesses a zinc finger domain with a tandem array of four FLYWCH zinc finger motifs at its N-terminus and a C-terminal domain that shares a 46% homology with GST. The gene maps to chromosome 3 at position 84C6. Further characterization of this protein shows that it localizes to the cytoplasm of fly cells and is expressed through all stages of fly embryonic development. It binds to glutathione-S agarose beads in vitro. These results indicate that this new protein belongs to the GST family, thus named a Drosophila GST-containing FLYWCH zinc finger protein (dGFZF).     

Comparative gene expression in the heads of Drosophila melanogaster and Tribolium castaneum and the segmental affinity of the Drosophila hypopharyngeal lobes

SUMMARY Drosophila melanogaster has long played an important role in debates surrounding insect and arthropod head segmentation. It is surprising, therefore, that one important feature of Drosophila head segmentation has remained controversial: namely the position of the boundary between the intercalary and mandibular segments. The Drosophila embryonic head has a pair of structures lying behind the stomodeum known as the hypopharyngeal lobes. Traditionally they have been seen as part of the intercalary segment. More recent work looking at the position of the lobes relative to various marker genes has been somewhat equivocal: segment polarity gene expression has been used to argue for a mandibular affinity of these lobes, while the expression of the anterior-most hox gene labial ( lab ) has supported an intercalary affinity. We have addressed the question of the segmental affinity of the hypopharyngeal lobes by conducting a detailed comparison of gene expression patterns between Drosophila and the red flour beetle Tribolium castaneum , in which the intercalary segment is unambiguously marked out by lab . We demonstrate that there is a large degree of conservation in gene expression patterns between Drosophila and Tribolium , and this argues against an intercalary segment affinity for the hypopharyngeal lobes. The lobes appear to be largely mandibular in origin, although some gene expression attributed to them appears to be associated with the stomodeum. We propose that the difficulties in interpreting the Drosophila head result from a topological shift in the Drosophila embryonic head, associated with the derived process of head involution.