The future of gene therapy. Cavazzana-Calvo, M. Thrasher, A. & Mavilio, F. Nature 3 March (2004). In the light of negative press, scepticism from colleagues and mixed reactions from regulators, the authors of this Commentary discuss the successes and failures of gene therapy, and what needs to be done to help revive this field.

Gene patenting and medical research: a view from a pharmaceutical company. Stott, M. & Valentine, J. Nature Reviews Drug Discovery April (2004).

siRNA: applications in functional genomics and potential as therapeutics. Dorsett, Y. & Tuschl, T. Nature Reviews Drug Discovery April (2004).

Developing a new paradigm for thymus organogenesis. Blackburn, C. C. & Manley, N. R. Nature Reviews Immunology April (2004). This Review discusses recent embryological, functional, genetic and molecular data that collectively support a new model of thymus organogenesis and patterning.

T-loops and the origin of telomeres. de Lange, T. Nature Reviews Molecular Cell Biology April (2004). An Opinion piece on the evolution of the telomerase-based system that eukaryotes use to maintain their linear chromosomes.

Genes and ligands for odorant, vomeronasal and taste receptors. Mombaerts, P. Nature Reviews Neuroscience April (2004).

Immunotherapeutic uses of CpG oligodeoxynucleotides. Klinman, D. M. Nature Reviews Immunology April (2004).

Knockdown by RNAi — proceed with caution. Samuel, C. E. Nature Biotechnology March (2004). Small interfering RNAs, synthesized using phage polymerases but not by chemical methods, can trigger the interferon response in mammalian cells; this News and Views piece emphasizes that caution is required when designing siRNAs to inhibit pathogens, such as viruses.

Making a better worm. Kopp, A. Nature Genetics March (2004). The author of this News and Views article discusses new work in Caenorhabditis elegans, which has shown that gene replacement can be used to distinguish between different models of phenotypic evolution.