Circadian Genetics

Association of the length polymorphism in the human Per3 gene with the delayed sleep-phase syndrome: does latitude have an influence on it?. Pereira, D. S. et al. Sleep 28, 29–32 (2005)

Obesity and metabolic syndrome in circadian Clock mutant mice. Turek, F. W. et al. Science 21 April 2005 (10.1126/science.1108750)

These papers highlight intriguing aspects of the role of circadian genetics in disease. Pereira et al. investigated the role of PER3, a circadian gene, in human delayed sleep-phase syndrome (DSPS). The association of a specific PER3 polymorphism with the syndrome was found to vary with latitude, indicating that the same circadian genotype responds differently to the distinct environmental cues provided at different geographical locations. Turek and colleagues showed that mice that are mutant for Clock, another circadian gene, develop obesity and a metabolic-syndrome phenotype. Levels of neurotransmitters involved in regulating energy balance were altered in these mice, indicating a direct link between the circadian system and metabolism.

Evolutionary Genetics

Genetic variance in female condition predicts indirect genetic variance in male sexual display traits. Petfield, D. et al. Proc. Natl Acad. Sci. USA 102, 6045–6050 (2005)

Indirect genetic effects (IGEs) occur when the genotype of one individual affects the phenotype of another. Although IGEs between related individuals are well studied, less is known about their importance in interactions between unrelated individuals. Using Drosophila serrata as a model, these authors demonstrated that the production of male pheromones, a sexual display trait, varies in response to genetic variance in the condition of unrelated females. IGEs might therefore have an important impact on sexual selection.

Gene Expression

Interchromosomal associations between alternatively expressed loci. Spilianakis, C. G. et al. Nature 8 May 2005 (10.1038/nature03574)

Recent work described how the T-helper-cell 2 (TH2) locus control region (LCR) co-ordinately regulates TH2 cytokine genes, which are spread over 120 kb, through interchromosomal interactions between the LCR and the cytokine loci in question. Spillanakis et al. used a chromosome-conformation capture technique to show that interactions between loci on different chromosomes (in this case, mouse chromosomes 10 and 11) also occur. This phenomenon might function in coordinating gene expression, and might also apply to other genes, such as those that encode olfactory receptors and globin proteins.