This week in PLOS Biology
In PLOS Biology this week, you can read about the generation of neural stem cells, compensatory evolution, the evolution of language and focusing of attention by the frontal and parietal areas of the cortex.
Stem cells are providing insight into embryo development and offering new approaches to clinical and therapeutic research. During embryo development, spinal cord and the adjacent paraxial mesoderm (which later forms muscle and bone) arise from precursors called neuromesodermal progenitors (NMPs). In new research published this week, Mina Gouti, James Briscoe and colleagues were able to make NMPs in vitro, and showed that in mice and human cells, the decision between spinal cord and mesoderm involves a gene, Brachyury, that promotes mesoderm production by inhibiting spinal cord generation. This could have important applications, as the production of neural stem cells is a desirable goal for therapeutic uses. Read more in the accompanying synopsis.
While core cellular processes are generally conserved during evolution, the constituent genes differ somewhat between related species with similar lifestyles. Why should this be so? In a large scale evolutionary experiment using baker’s yeast, Béla Szamecz, Csaba Pál and colleagues set out to show that organisms can recover fitness by the accumulation of compensatory mutations elsewhere in the genome. They took 180 strains of yeast, each lacking a specific gene which compromised fitness, and allowed them to evolve through 400 generations to see if the yeast could ultimately compensate for the lost gene. Interestingly, 68% of the genotypes reached near wild-type fitness through adaptive mutations. Genomic analysis revealed that compensatory mutations were generally specific to the functional defect incurred, but that the evolutionary outcomes were not phenotypically equivalent.
In a new essay published this week, Johan Bolhuis, Ian Tattersall, Noam Chomsky and Robert Berwick discuss the controversial topic of how language evolved. The authors begin by explaining that the definition of language itself is not even clearly defined, although they argue for the theory that syntax is the key feature of language. Using this idea, its evolution is very hard to study – syntax having no equivalent in non-humans. Bolhuis and colleagues argue that the appearance of symbolic thought arose around 100,000 years ago, when Homo sapiens first produced symbolic artefacts.
In their new research paper, Sara Szczepanski, Robert Knight and colleagues addressed the important question of how the frontal and parietal areas of the cerebral cortex work together to focus attention. They applied electrodes directly onto the cortex of patients who were about to undergo surgical treatment for epilepsy and asked them to perform a reaction time task. They conclude that coupling between delta/theta phase and high gamma amplitude components of electrical brain activity serves to coordinate information within – and perhaps between – frontal and parietal areas during coordination of visuospatial attention.