Directed cell migration and target recognition are critical for the development of both the nervous and muscular systems. Molecular mechanisms that control these processes in the nervous system have been intensively studied, whereas those that act during muscle development are still largely uncharacterized. Here we identify a transmembrane protein, Kon-tiki (Kon), that mediates myotube target recognition in the Drosophila embryo. Kon is expressed in a specific subset of myotubes and is required autonomously for these myotubes to recognize their tendon cell targets and to establish a stable connection. Kon is enriched at myotube tips during targeting and signals through the intracellular adaptor Dgrip in a conserved molecular pathway. Forced overexpression of Kon stimulates muscle motility. We propose that Kon promotes directed myotube migration and transduces a target-derived signal that initiates the formation of a stable connection.

Germ cells, the cells that give rise to sperm and egg, maintain the potential to recreate all cell types in a new individual. This wide developmental potential, or totipotency, is manifested in unusual tumors called teratomas, in which germ cells undergo somatic differentiation. Although recent studies have implicated RNA regulation, the mechanism that normally prevents the loss of germ cell identity remains unexplained. In C. elegans, a teratoma is induced in the absence of the conserved RNA-binding protein GLD-1. Here, we demonstrate that GLD-1 represses translation of CYE-1/cyclin E during meiotic prophase, which prevents germ cells from re-entering mitosis and inducing embryonic-like transcription. We describe a mechanism that prevents precocious mitosis in germ cells undergoing meiosis, propose that this mechanism maintains germ cell identity by delaying the onset of embryonic gene activation until after fertilization, and provide a paradigm for the possible origin of human teratomas.

Although the decision between stem cell self-renewal and differentiation has been linked to cell-cycle modifications, our understanding of cell-cycle regulation in stem cells is very limited. Here, we report that FBF/Pumilio, a conserved RNA-binding protein, promotes self-renewal of germline stem cells by repressing CKI-2 Cip/Kip , a Cyclin E/Cdk2 inhibitor. We have previously shown that repression of CYE-1 (Cyclin E) by another RNA-binding protein, GLD-1/Quaking, promotes germ cell differentiation. Together, these findings suggest that a post-transcriptional regulatory circuit involving FBF and GLD-1 controls the self-renewal versus differentiation decision in the germline by promoting high CYE-1/CDK-2 activity in stem cells, and inhibiting CYE-1/CDK-2 activity in differentiating cells.

Single nucleotide polymorphisms (SNPs) are useful markers for genetic mapping experiments in model organisms. Here we report the establishment of a high-density SNP map and high-throughput genotyping assays for Drosophila melanogaster. Our map comprises 27,367 SNPs in common laboratory Drosophila stocks. These SNPs were clustered within 2,238 amplifiable markers at an average density of 1 marker every 50.3 kb, or 6.3 genes. We have also constructed a set of 62 Drosophila stocks, each of which facilitates the generation of recombinants within a defined genetic interval of 1-2 Mb. For flexible, high-throughput SNP genotyping, we used fluorescent tag-array mini-sequencing (TAMS) assays. We designed and validated TAMS assays for 293 SNPs at an average resolution of 391.3 kb, and demonstrated the utility of these tools by rapidly mapping 14 mutations that disrupt embryonic muscle patterning. These resources enable high-resolution high-throughput genetic mapping in Drosophila.

Introductions of alien freshwater fish species into the Mediterranean-climatic South-west Coast Drainage Division of Australia have impacted a highly endemic (≈82%) yet depauperate (11 species) native freshwater fish fauna. This study updates the current known introduced freshwater fishes in Western Australia, assesses the historic rate of introductions and how habitat, water quality and climatic changes have facilitated those introductions. South-western Australia has undergone a ≈63% increase in alien freshwater fish introductions since 1970 (44% increase over the past decade) to 13 species; overtaking the number of native fishes. Aquarium species represent 80% of the latest introductions (46% of total number) and the majority (54%) of introduced fishes in the region are of sub-tropical or tropical origin. As found elsewhere, species with broad environmental tolerances and generalist diets are likely to continue to be the main colonizers in this region. We propose that past and future climatic and habitat changes in the Mediterranean-climatic south-west region will facilitate continued invasion of tropical and sub-tropical aquarium fishes and that strategic monitoring, control and public education programs are required to halt future introductions.