The solution structure of the forkhead box-O DNA binding domain of Brugia malayi DAF-16a.

Brugia malayi is a parasitic nematode that causes lymphatic filariasis in humans. Here the solution structure of the forkhead DNA binding domain of Brugia malayi DAF-16a, a putative ortholog of Caenorhabditis elegans DAF-16, is reported. It is believed to be the first structure of a forkhead or winged helix domain from an invertebrate. C. elegans DAF-16 is involved in the insulin/IGF-I signaling pathway and helps control metabolism, longevity, and development. Conservation of sequence and structure with human FOXO proteins suggests that B. malayi DAF-16a is a member of the FOXO family of forkhead proteins.

Using clickers in nonmajors- and majors-level biology courses: student opinion, learning, and long-term retention of course material.

Student response systems (clickers) are viewed positively by students and instructors in numerous studies. Evidence that clickers enhance student learning is more variable. After becoming comfortable with the technology during fall 2005-spring 2006, we compared student opinion and student achievement in two different courses taught with clickers in fall 2006. One course was an introductory biology class for nonmajors, and the other course was a 200 level genetics class for biology majors. Students in both courses had positive opinions of the clickers, although we observed some interesting differences between the two groups of students. Student performance was significantly higher on exam questions covering material taught with clickers, although the differences were more dramatic for the nonmajors biology course than the genetics course. We also compared retention of information 4 mo after the course ended, and we saw increased retention of material taught with clickers for the nonmajors course, but not for the genetics course. We discuss the implications of our results in light of differences in how the two courses were taught and differences between science majors and nonmajors.

Orthologues of the Drosophila melanogaster E75 molting control gene in the filarial parasites Brugia malayi and Dirofilaria immitis.

Filarial parasites cause debilitating diseases in humans and domesticated animals. Brugia malayi and Dirofilaria immitis are transmitted by mosquitoes and infect humans and dogs, respectively. Their life cycle is punctuated by a series of cuticular molts as they move between different hosts and tissues. An understanding of the genetic basis for these developmental transitions may suggest potential targets for vaccines or chemotherapeutics. Nuclear receptor (NR) proteins have been implicated in molting in the free-living nematode Caenorhabditis elegans and have well characterized roles in molting during larval development of Drosophila melanogaster. For example, the D. melanogaster E75 (NR1D3) NR gene is required for molting and metamorphosis, as well as egg chamber development in adult females. We have identified Bm-nhr-11and Di-nhr-6, B. malayi and D. immitis orthologues of E75. Both genes encode canonical nuclear receptor proteins, are developmentally regulated, and are expressed in a sex-specific manner in adults.

Expression and function of conserved nuclear receptor genes in Caenorhabditis elegans.

The Caenorhabditis elegans genome encodes 284 nuclear receptor (NR) genes. Among these 284 NR genes are 15 genes conserved among the Metazoa. Here, we analyze the expression and function of eight heretofore uncharacterized conserved C. elegans NR genes. Reporter gene analysis demonstrates that these genes have distinct expression patterns and that a majority of the C. elegans cell types express a conserved NR gene. RNA interference with NR gene function resulted in visible phenotypes for three of the genes, revealing functions in various processes during postembryonic development. Five of the conserved NR genes are orthologs of NR genes that function during molting and metamorphosis in insects. Functional studies confirm a role for most of these 'ecdysone cascade' NR orthologs during the continuous growth and dauer molts. Transcript levels for these genes fluctuate in a reiterated pattern during the molting cycles, reminiscent of the expression hierarchy observed in the insect ecdysone response. Together, these analyses provide a foundation for further dissecting the role of NRs in nematode development as well as for evaluating conservation of NR functions among the Metazoa.

Dirofilaria immitis encodes Di-nhr-7, a putative orthologue of the Drosophila ecdysone-regulated E78 gene.

Filarial parasites are responsible for several serious human diseases with symptoms such as lymphoedema, elephantiasis, and blindness. An understanding of how these parasites pass through developmental checkpoints may elucidate the general mechanisms of these illnesses and suggest potential targets for intervention. A useful model system for the study of human filariasis is the related nematode Dirofilaria immitis, the causative agent of dog heartworm disease. In D. immitis, molting from the third to the fourth larval stage can be induced in vitro by the insect hormone 20-OH ecdysone, suggesting that ecdysone, or some related hormone, may play a similar role in the development of D. immitis. Ecdysone has a well-characterized developmental role in insects, where it is involved in the control of molting and metamorphosis. We have identified a D. immitis orthologue of the Drosophila ecdysone response early gene E78, a member of the nuclear receptor (NR) superfamily. The D. immitis gene, Di-nhr-7 (NR1E1) encodes at least three isoforms, including two potential negative regulatory isoforms, and is expressed in a sex-specific manner. An MBP/Di-NHR-7 fusion protein is able to bind to DNA response elements that are recognized by the closely related mammalian NR Rev-erb(alpha).