Genomics

Initial sequence and comparative analysis of the cat genome. Pontius, J. U. et al. Genome Res. 17, 1675–1689 (2007)

The assembly and annotation of the domestic cat (Felis catus) genome has been reported. The genome of Cinnamon, an Abyssinian cat, was sequenced at twofold coverage and annotated by comparison with the genomes of other sequenced mammals. The analysis identified chromosomal rearrangements, thousands of genomic variants, microRNAs and many transposable elements. The sequence will be relevant not only for improving cat health but also for mapping disease-susceptibility genes, including those for the >250 hereditary disorders shared with humans.

Cancer

An elaborate pathway required for Ras-mediated epigenetic silencing. Gazin, C., Wajapeyee, N. et al. Nature 449, 1073–1077 (2007)

A genome-wide RNAi screen in human cancer cells in culture identifies a network of genes that converts a normal cell to a cancerous one. KRAS-transformed cells were screened for epigenetic regulators in the Ras pathway that silence the pro-apoptotic gene FAS. The 28 epigenetic modifiers — most of which were not previously connected to Ras — belong to a common pathway of 'Ras epigenetic silencing factors' that also silence other, unrelated genes that are required for cell transformation.

Genome evolution

A sex-ratio meiotic drive system in Drosophila simulans . I: An autosomal suppressor. Tao, Y. et al. PLoS Biol. 5, e292 (2007)

A sex-ratio meiotic drive system in Drosophila simulans . II: An X-linked distorter. Tao, Y. et al. PLoS Biol. 5, e293 (2007)

Sex-ratio distortion occurs in many species and leads to the overrepresentation of one sex among offspring. Two papers identify for the first time, in Drosophila simulans, an X-linked distorter gene (DOX) and the autosomal gene (not much yang, NMY) that has evolved to suppress the action of the distorter. The sequence similarity of the two genes suggests that the suppression occurs by RNAi. The authors also report that the physiological cause of the distortion is a failure to produce mature sperm.

Gene networks

A gene regulatory network subcircuit drives a dynamic pattern of gene expression. Smith, J. et al. Science 318, 794–797 (2007)

The authors have defined a cis-regulatory subcircuit that defines the dynamic expression pattern of genes in the early sea urchin embryo. Blimp1 is expressed at the centre of an expanding ring at early cleavage stages and, while the expression domain moves radially outwards, it is progressively extinguished in the more central domains. In the experimentally resolved circuit, which involves at least three key genes, extinction of Blimp1 expression is caused by autorepression, whereas its radial expansion follows Wnt8 signalling.