Saturday, March 11, 2006
[evomech] Separation of Man and Ape Down to Gene Expression (PR + Article)
1) Separation of Man and Ape Down to Gene Expression
Humans and chimpanzees have in common more than 98 percent of DNA and 99 percent of genes. Yet, in looks and behavior we are very different from them. For more than 30 years--well before either the human or chimpanzee genome had been sequenced--scientists have speculated that this might be due to the way that the common genes express themselves rather than differences in the genes themselves. A new comparison published in Nature seems to prove that theory.
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2) Expression profiling in primates reveals a rapid evolution of human transcription factors
[Gilad et al, Nature, March '06]
Although it has been hypothesized for thirty years that many human adaptations are likely to be due to changes in gene regulation1, almost nothing is known about the modes of natural selection acting on regulation in primates. Here we identify a set of genes for which expression is evolving under natural selection. We use a new multi-species complementary DNA array to compare steady-state messenger RNA levels in liver tissues within and between humans, chimpanzees, orangutans and rhesus macaques. Using estimates from a linear mixed model, we identify a set of genes for which expression levels have remained constant across the entire phylogeny (approx70 million years), and are therefore likely to be under stabilizing selection. Among the top candidates are five genes with expression levels that have previously been shown to be altered in liver carcinoma. We also find a number of genes with similar expression levels among non-human primates but significantly elevated or reduced expression in the human lineage, features that point to the action of directional selection. Among the gene set with a human-specific increase in expression, there is an excess of transcription factors; the same is not true for genes with increased expression in chimpanzee.
Full text at:
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