In this week's Science, an international research team presents a global map of genetic diversity within species, revealing that for amphibians and mammals, such diversity is highest near the equator and that it is influenced by humans. Using publicly available DNA databases, investigators focused on a subset of DNA representing 4,500 amphibian and mammalian species, matching the data with geographic information. In all cases, genetic diversity was higher in the tropics than in cold climates. For amphibians, this diversity was lower in locations most transformed by human activity, while for mammals, genetic diversity was highest in regions with an intermediate level of human transformation. In a related editorial, Henrique Pereira says that these findings support the hypothesis of evolutionary speed, which is based on the notion that hotter climates lead to increased mutation rates. GenomeWeb has more on this study here.
Also in Science, two separate research teams report data on using the genome-editing technology CRISPR-Cas9 to assess how non-coding genomic regions influence gene regulation related to processes controlling drug resistance or disease. In one study, researchers pooled multiple libraries of CRISPR-Cas9 single guide RNA libraries to mutate non-coding regions surrounding genes linked to resistance to a common cancer drug. By looking at how these mutations affected the expression of the proximal genes involved in resistance to the drug, the researchers were able to determine whether these non-coding regions alter the genetic basis of resistance. Notably, they found that expression of one gene involved in resistance to this drug was significantly reduced following mutation of the surrounding non-coding region. In another study, investigators used CRISPR interference — a new sequence-specific genetic modification technique that acts during transcription — to study the non-coding regions around two genes that control the proliferation of erythroleukemia cells, and found major regulatory elements around the two loci that appear to interact with the genes. GenomeWeb also covers these papers here.