Target highlights in CASP13: Experimental target structures through the eyes of their authors

The functional and biological significance of selected CASP13 targets are described by the authors of the structures. The structural biologists discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP13 experiment.     

A cornucopia of delights for the mouse fancier

A report on the Mouse Molecular Genetics meeting, Hinxton, UK, 5-9 September 2007.     

In vivo imaging and differential localization of lipid-modified GFP-variant fusions in embryonic stem cells and mice

The visualization of live cell behaviors operating in situ combined with the power of mouse genetics represents a major step toward understanding the mechanisms regulating embryonic development, homeostasis, and disease progression in mammals. The availability of genetically encoded fluorescent protein reporters, combined with improved optical imaging modalities, have led to advances in our ability to examine cells in vivo. We developed a series of lipid-modified fluorescent protein fusions that are targeted to and label the secretory pathway and the plasma membrane, and that are amenable for use in mice. Here we report the generation of two strains of mice, each expressing a spectrally distinct lipid-modified GFP-variant fluorescent protein fusion. The CAG::GFP-GPI strain exhibited widespread expression of a glycosylphosphatidylinositol-tagged green fluorescent protein (GFP) fusion, while the CAG::myr-Venus strain exhibited widespread expression of a myristoyl-Venus yellow fluorescent protein fusion. Imaging of live transgenic embryonic stem (ES) cells, either live or fixed embryos and postnatal tissues demonstrated that glycosylphosphatidyl inositol- and myristoyl-tagged GFP-variant fusion proteins are targeted to and serve as markers of the plasma membrane. Moreover, our data suggest that these two lipid-modified protein fusions are dynamically targeted both to overlapping as well as distinct lipid-enriched compartments within cells. These transgenic strains not only represent high-contrast reporters of cell morphology and plasma membrane dynamics, but also may be used as in vivo sensors of lipid localization. Furthermore, combining these reporters with the study of mouse mutants will be a step forward in understanding the inter- and intracellular behaviors underlying morphogenesis in both normal and mutant contexts.     

Can mammalian cloning combined with embryonic stem cell technologies be used to treat human diseases?

Cloning is commonly perceived as a means of generating genetically identical individuals, but it can also be used to obtain genetically matched embryo-derived stem cells, which could potentially be used in the treatment of patients. A recent report offers the first 'proof of principle' of such cloning for therapeutic purposes, referred to as nuclear transplantation to produce stem cells for autologous transplantation.     

Expression of Lex antigen in Schistosoma japonicum and S.haematobium and immune responses to Lex in infected animals: lack of Lex expression in other trematodes and nematodes

Adults of the human parasitic trematode Schistosoma mansoni, which causes hepatosplenic/intestinal complications in humans, synthesize glycoconjugates containing the Lewis x (Lex) Galbeta1-->4(Fucalpha1-- >3)GlcNAcbeta1-->R, but not sialyl Lewis x (sLex), antigen. We now report on our analyses of Lexand sLexexpression in S.haematobium and S.japonicum, which are two other major species of human schistosomes that cause disease, and the possible autoimmunity to these antigens in infected individuals. Antigen expression was evaluated by both ELISA and Western blot analyses of detergent extracts of parasites using monoclonal antibodies. Several high molecular weight glycoproteins in both S. haematobium and S. japonicum contain the Lexantigen, but no sialyl Lexantigen was detected. In addition, sera from humans and rodents infected with S.haematobium and S.japonicum contain antibodies reactive with Lex. These results led us to investigate whether Lexantigens are expressed in other helminths, including the parasitic trematode Fasciola hepatica , the parasitic nematode Dirofilaria immitis (dog heartworm), the ruminant nematode Haemonchus contortus , and the free-living nematode Caenorhabditis elegans . Neither Lexnor sialyl-Lexis detectable in these other helminths. Furthermore, none of the helminths, including schistosomes, express Lea, Leb, Ley, or the H- type 1 antigen. However, several glycoproteins from all helminths analyzed are bound by Lotus tetragonolobus agglutinin , which binds Fucalpha1-->3GlcNAc, and Wisteria floribunda agglutinin, which binds GalNAcbeta1-->4GlcNAc (lacdiNAc or LDN). Thus, schistosomes may be unique among helminths in expressing the Lexantigen, whereas many different helminths may express alpha1,3-fucosylated glycans and the LDN motif.