Evaluation of large volume yeast interfering RNA lure-and-kill ovitraps for attraction and control of Aedes mosquitoes.

Aedes mosquitoes (Diptera: Culicidae), principle vectors of several arboviruses, typically lay eggs in man-made water-filled containers located near human dwellings. Given the widespread emergence of insecticide resistance, stable and biofriendly alternatives for mosquito larviciding are needed. Laboratory studies have demonstrated that inactivated yeast interfering RNA tablets targeting key larval developmental genes can be used to facilitate effective larvicidal activity while also promoting selective gravid female oviposition behaviour. Here we examined the efficacy of transferring this technology toward development of lure-and-kill ovitraps targeting Aedes aegypti (L.) and Aedes albopictus (Skuse) female mosquitoes. Insectary, simulated field and semi-field experiments demonstrated that two mosquito-specific yeast interfering RNA pesticides induce high levels of mortality among larvae of both species in treated large volume containers. Small-scale field trials conducted in Trinidad, West Indies demonstrated that large volume ovitrap containers baited with inactivated yeast tablets lure significantly more gravid females than traps containing only water and were highly attractive to both A. aegypti and A. albopictus females. These studies indicate that development of biorational yeast interfering RNA-baited ovitraps may represent a new tool for control of Aedes mosquitoes, including deployment in existing lure-and-kill ovitrap technologies or traditional container larviciding programs.

Semaphorins at the interface of development and cancer.

Semaphorins (Semas), a family of evolutionarily conserved secreted and transmembrane proteins, were initially identified as axon guidance regulators and have since been implicated in the development of a number of other tissues. Sema signaling also regulates a variety of processes that are linked to cancer (i.e. metastasis, cell migration, cell growth). The mechanisms by which Sema signaling regulates axonogenesis and tumorigenesis are strikingly similar, making advances in either field applicable to the alternate discipline. Here, recent advances in understanding the roles of Semas in development and cancer, as well as the therapeutic potential for targeting this signaling pathway in human cancers, are reviewed.

Netrin and DCC: axon guidance regulators at the intersection of nervous system development and cancer.

In recent years, a number of axon guidance genes, including Netrin (Net) and Deleted in Colorectal Cancer (DCC), have been implicated in human cancers. Many of the hallmarks of human cancer, such as cell growth, invasion, evasion of apoptosis, and formation of a blood supply to the tumor, involve cellular processes that are critical during nervous system development. Here, the roles of Net-DCC in the regulation of these cellular processes in tumors and developing neurons are discussed. The advantages of using Drosophila to study the function of Net-DCC and other axon guidance molecules in these cellular processes, as well as the potential for cancer therapeutics targeting Net-DCC are highlighted.

Analysis of molecular marker expression reveals neuronal homology in distantly related arthropods.

Morphological studies suggest that insects and crustaceans of the Class Malacostraca (such as crayfish) share a set of homologous neurons. However, expression of molecular markers in these neurons has not been investigated, and the homology of insect and malacostracan neuroblasts, the neural stem cells that produce these neurons, has been questioned. Furthermore, it is not known whether crustaceans of the Class Branchiopoda (such as brine shrimp) or arthropods of the Order Collembola (springtails) possess neurons that are homologous to those of other arthropods. Assaying expression of molecular markers in the developing nervous systems of various arthropods could resolve some of these issues. Here, we examine expression of Even-skipped and Engrailed, two transcription factors that serve as insect embryonic CNS markers, across a number of arthropod species. This molecular analysis allows us to verify the homology of previously identified malacostracan neurons and to identify additional homologous neurons in malacostracans, collembolans and branchiopods. Engrailed expression in the neural stem cells of a number of crustaceans was also found to be conserved. We conclude that despite their distant phylogenetic relationships and divergent mechanisms of neurogenesis, insects, malacostracans, branchiopods and collembolans share many common CNS components.

Genetic separation of the neural and cuticular patterning functions of gooseberry.

In addition to their role in the specification of the epidermal pattern in each segment, several segment polarity genes, including gooseberry (gsb), specify cell fate in the Drosophila central nervous system (CNS). Analyses of the gsb CNS phenotype have been complicated by the fact that the previously available gsb mutants, all caused by cytologically visible deficiencies, have severe segmentation defects and also lack a number of additional genes. We have characterized two novel gsb mutants which, due to their hypomorphic nature, have CNS defects, but have only weak or no segmentation defects. These gsb alleles, as well as gsb rescue experiments, have allowed us to determine which aspects of the deficiency mutant phenotypes can be attributed to loss of gsb. gsb mutants lack U and CQ neurons, have duplicated RP2 neurons, and display posterior commissure defects. gsb neural defects, as well as the gsb cuticle defect, are differentially sensitive to the level of functional Gsb. We have used one of the novel gsb alleles in order to understand the genetic interactions between gsb, wingless (wg), and patched (ptc) during the patterning of the ventral neuroectoderm. In contrast to epidermal patterning, where Gsb is required to maintain wg transcription, we find that Gsb antagonizes the Wg signal that confers neuroblast (NB) 4-2 fate.