Evo–Devo

Ancestral role of caudal genes in axis elongation and segmentation. Copf, T. et al. Proc. Natl Acad. Sci. USA 101, 17711–17715 (2004)

Caudal genes are known for their role in posterior patterning. By using RNAi, Copf et al. showed that loss of caudal in two arthropods (the Tribolium beetle and the Artemia crustacean) causes axis truncation and disrupts segment formation. Unlike in Drosophila, segments are laid down sequentially in these arthropods, just as they are during vertebrate somitogenesis. Given this similarity and the involvement of vertebrate caudal homologues (Cdx genes) in axis elongation and somitogenesis, these might represent ancestral, evolutionarily conserved caudal function.

Technology

Using protein–DNA chimeras to detect and count small numbers of molecules. Burbulis, I. et al. Nature Methods 2, 31–37 (2005)

The authors describe a powerful new tool for detecting a range of biological targets. The key to the technique, the sensitivity of which surpasses that of the routinely used ELISA, is a DNA–protein hybrid molecule (the 'tadpole'): the 'head' is made up of protein that has a targeted affinity for a specific molecule; the 'tail' is a unique DNA tag that allows PCR-based quantification. The two halves are joined in a naturally occurring splicing reaction.

Epigenetics

Histone demethylation mediated by the nuclear amine oxidase homolog LSD1. Shi, Y. et al. Cell 119, 941–953 (2004)

Histone methylation levels are crucial in the regulation of gene expression. In contrast to acetylation (both acetylases and deacetylases are known), methylation was thought to be a permanent modification. The authors provide evidence that LSD1, a nuclear-localized homologue of amine oxidases, functions as a histone demethylase of histone H3 lysine 4. Since this modification is linked with active transcription, LSD1, which is conserved from fission yeast to humans, is probably a transcriptional co-repressor.

Human genetics

The influence of CCL3L1 gene-containing segmental duplications on HIV-1/AIDS susceptibility. Gonzales, Z. et al. Science 6 January 2005 (10.1126/science.1101160)

Segmental duplications are enriched for genes that are involved in immunity, although the consequences of this fact remain unknown. The authors found that copy number of CCL3L1, a gene that encodes a ligand for the HIV co-receptor CCR5, varies significantly among individuals and populations. Fewer CCL3L1 copies mean greater susceptibilty to HIV infection, whereas high levels of CCL3L1 are thought to block the association between CCR5 and HIV that is required for virus internalization. These findings support the crucial involvement of CCR5 and its ligands in determining HIV pathogenesis.