Evo–devo

Microevolutionary analysis of the nematode genus Pristionchus indicates a recent evolution of redundant developmental mechanisms during vulva formation. Srinivasan, J. et al. Evol. Dev. 3, 229–240 (2001) [PubMed]

Studying closely related species or subpopulations can help to discover mutations that are important for phenotypic variation. Here, 13 lab strains of the nematode genus Pristionchus were divided into four different species on the basis of mating experiments and genetic sequence comparisons, and then molecular variation between strains was studied. As morphologically distinct strains were identical at tested polymorphic loci (using Amplified Fragment Length Polymorphism analysis), developmental differences might rely only on a small number of genetic changes.

Microbial genomics

Evolutionary genomics of Staphylococcus aureus : insights into the origin of methicillin-resistant strains and the toxic shock syndrome epidemic. Fitzgerald, J. R. et al. Proc. Natl Acad. Sci. USA 98, 8821–8826 (2001) [PubMed]

Complete genome sequence of a virulent isolate of Streptococcus pneumoniae. Tettelin, H. et al. Science 293, 498–506 (2001) [PubMed]

Comparative genomic studies of microorganisms are providing new information on the origins and variation of important human pathogens. Fitzgerald et al. used genomic microarrays to compare the genomes of 36 clinical isolates of Staphylococcus aureus with varying pathogenicity. They found substantial genomic variation and showed that a 1970's epidemic of toxic shock syndrome could not have been caused by the rapid spread of a hypervirulent strain of S. aureus, resolving a long-standing controversy in this field. With the completion of the genome sequence of Streptococcus pneumoniae, by Tettelin and colleagues, similar work can now be carried out on this pathogen. Indeed, a comparison with two clinical isolates reveals striking variation in genes likely to be involved in pathogenesis.

Technology

Diphtheria toxin receptor-mediated conditional and targeted cell ablation in transgenic mice. Saito, M. et al. Nature Biotechnol. 19, 746–750 (2001) [PubMed]

Saito et al. have used a transgenic approach to ablating cells by introducing into mice a transgene that encodes a human diphtheria toxin (DT) receptor driven by a liver-specific promoter. The hepatocytes of transgenic mice exposed to DT undergo damage in a dose-dependent manner, leading to hepatitis. This approach could be used to ablate other cell types in DT-insensitive animals for studies of human disease and tissue regeneration.