This Week in PLOS Biology
In PLOS Biology this week, you can read about social learning in chimps, how the central and peripheral nervous systems stay separate, how the bird wrist evolved, synchronising circadian clocks and a protein essential to the TFIIH complex.
Social Learning of Tool Use in Wild Chimpanzees
Chimpanzees are widely considered as the most ‘‘cultural’’ of all non-human animals, despite the lack of direct evidence for the spread of novel behaviours through social learning in the wild. In their new paper, Catherine Hobaiter, Thibaud Gruber and colleagues developed new dynamic social network analyses to test the spread of two behaviours in a group of wild chimps in Budongo Forest, Uganda. These behaviours were ‘moss sponging’ (using moss to produce a sponge) and ‘leaf sponge re-use’ (using a sponge discarded by another individual). They found strong evidence for social transmission of moss sponging among this group of chimps.
See moss-sponging behaviour in chimps in these videos:
Separating Nervous Systems – it’s All in the Wrapper
The points where axons cross between the central and peripheral nervous systems (CNS and PNS) are known as transition zones, but the mechanisms that establish and maintain this precise segregation are unknown. Cody Smith, Sarah Kucenas and colleagues used in vivo time-lapse imaging in zebrafish to identify a novel cell type responsible for stopping CNS-residing glia from entering the PNS. They call these cells ‘motor exit point glia’. These results identify an aspect of peripheral nerve composition that may be pertinent in human health and disease.
How Dinosaur Arms Turned into Bird Wings
Since their emergence from early dinosaurs, birds have reduced the number of bones in their wrist, but the origins and identity of those remaining are hard to trace. Wrists went from straight to bent and hyperflexible, allowing birds to fold their wings neatly against their bodies when not flying. In their new paper in PLOS Biology, João Francisco Botelho, Alexander Vargas and colleagues draw on the fields of embryology and paleontology to resolve this puzzle. Their study integrates paleontological and developmental data (including immunostaining of embryos across a wide range of species) and clarifies the relationship between each of the four ossifications in birds and those found in non-avian dinosaurs. Read more in the accompanying Synopsis.
Circadian molecular clocks are essential for maintaining daily cycles in animal behaviour and we have a good understanding of how these clocks work in individual pacemaker neurons. However, the accuracy of these individual clocks is meaningless unless they are synchronized with one another. Ben Collins, Justin Blau and colleagues discovered that in the fruit fly Drosophila melanogaster, circadian pacemaker neurons are regulated by two synchronizing signals (the neuropeptide PDF and glutamate) that are released at opposite times of day, generating rhythmic changes in intracellular cyclic AMP.
XPD – Different Jobs in Repair and Transcription
The multiprotein complex TFIIH is crucially involved in two fundamental cellular processes—the transcription of genes by RNA polymerase II and the repair of UV-damaged DNA by a mechanism called nucleotide excision repair (NER). A helicase enzyme called XPD is part of the TFIIH complex, but it’s unclear which properties of XPD are required for which of TFIIH’s two cellular roles. Jochen Kuper, Caroline Kisker and colleagues found that in DNA repair, this protein works as an enzyme, but for transcription it is merely required as a structural protein to hold TFIIH together.