Research Highlights | Nature Reviews Genetics

Evolution of a transcriptional repression domain in an insect Hox protein.Galant, R. et al. Nature 415, 910–913 (2002)

Hox protein mutation and macroevolution of the insect body plan.Ronshaugen, M. et al. Nature 415, 914–917 (2002)

Mutations in Hox genes have often been implicated in large shifts in animal morphology, either because of an altered expression pattern of Hox transcription factors or due to variations in

their DNA binding specificity. These two studies have identified mutations outside the DNA binding domain that have been instrumental in the evolution of insects (such as Drosophila), which

have six legs, from their multiple-limbed ancestors. The focus of the two papers is the Hox gene Ubx: this gene can repress limb development in insects because of an Ala-rich stretch in the

protein's carboxyl terminus. In two taxa that are related to insects, Ubx promotes limb development either because the repressive domain is counteracted by a second domain (in crustaceans)

or, as in the more distantly related velvet worms, it is missing altogether.

Heterogeneity of linkage disequilibrium in human genes has implications for association studies of common disease.Tiret, L. et al. Hum. Mol. Genet. 11, 419–429 (2002)

Genome-wide studies have shown that linkage disequilibrium (LD) is not uniformly distributed across the genome but little is known of LD structure around individual genes. To address this,

Tiret et al. genotyped 750 Europeans for 228 polymorphisms in 50 candidate cardiovascular disease genes. They report that non-synonymous (NS) polymorphisms often occur at a low frequency and

are often in negative LD with other markers, indicating that the effects of a NS polymorphism might not always be detectable from a nearby marker.

Colorectal cancer in mice genetically deficient in the mucin Muc2.Velcich, A. et al. Science 295, 1726–1729 (2002)

Mucins are the main component of the mucus that lubricates and protects the gastrointestinal epithelium. Because altered expression and glycosylation of mucins has been observed in

colorectal cancers, Velcich et al. knocked out mucin 2 (Muc2) — which encodes the most abundant intestinal mucin — in mice. Muc2−/− mice develop with aberrant crypts and altered epithelial

cell maturation and migration. Most importantly, they often develop small intestinal adenomas that become invasive adenocarcinomas and rectal tumours, indicating that Muc2 might suppress

colorectal tumour formation.

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