Evolutionary genetics

Birth and adaptive evolution of a hominoid gene that supports high neurotransmitter flux. Burki, F. & Kaessmann, H. Nature Genet. 36, 1061–1063 (2004)

There are two glutamate dehydrogenase genes in humans: GLUD1 — a housekeeping gene — and GLUD2, which is expressed specifically in neural tissue and testis. The authors show that GLUD2 originated by retrotransposition from GLUD1 in our ancestor, 23 Mya. The changes that give GLUD2 its tissue specific properties are a result of positive selection, following a duplication event. GLUD2 probably contributed to enhanced brain function in humans and apes, and has also been implicated in late memory formation.

Population genetics

Global patterns of human mitochondrial DNA and Y-chromosome structure are not influenced by higher migration rates of females versus males. Wilder, J. A. et al. Nature Genet. 36, 1122–1125 (2004)

Genetic evidence supports demic diffusion of Han culture. Wen, B. et al. Nature 431, 302–305 (2004)

These studies analyse the effects of historical migration on human population structure. Wen et al. examined patterns of Y-chromosome and mitochondrial DNA (mtDNA) variation to study the spread of the Han Chinese culture. Their results indicate that this spread followed migration of the Han people, rather than diffusion of the culture through social interchange without genetic mixing, and show that males had a greater role than females in this expansion. Wilder et al. tested the theory that population structures have been more strongly influenced by female migration than that of males due to patrilocality, which occurs when females move to the locality of their spouses following marriage. Analysis of genetic variation between ten populations from different global regions showed that this is not the case, at least at the continental and global level, as similar levels of variation for Y-chromosomes and mtDNA indicate roughly equal contributions of male and female migration.

Evolutionary genetics

Regulatory evolution across the protein interaction network. Lemos, B. et al. Nature Genet. 36, 1059–1060 (2004)

These authors showed that, for a specific gene, the number of interactions that its protein product participates in is negatively correlated with the level of variation in gene expression, both within and between species. Furthermore, for pairs of interacting genes, levels of variation in gene expression were more similar than for randomly assigned pairs. These results indicate that protein-protein interactions might have an important role in constraining evolutionary changes in gene regulation.