Schmitt, C. | bioRxiv Science

bioRxiv2018

Mapping of TNTs using Correlative Cryo-Electron Microscopy Reveals a Novel Structure

The harmonious orchestration of intercellular communication is essential for multicellular organisms. One mechanism by which cells communicate is through long, actin-rich membranous protrusions, called tunneling nanotubes, that allow for the intercellular transport of various cargoes, including viruses, organelles, and proteins between the cytoplasm of distant cells in vitro and in vivo. Over the last decade, studies have focused on their functional role but information regarding their structure and the differences with other cellular protrusions such as filopodia, is still lacking. Here, we report the structural characterization of tunneling nanotubes using correlative light- and cryo-electron microscopy approaches. We demonstrate their structural identity compared to filopodia by showing that they are comprised of a bundle of functional individual Tunneling Nanotubes containing membrane-bound compartments and allowing organelle transfer.

cell biology↗

bioRxiv2016

Ancient hybridization and strong adaptation to viruses across African vervet monkey populations

Vervet monkeys (genus Chlorocebus, also known as African green monkeys), are highly abundant in savannahs and riverine forests throughout sub-Saharan Africa. They are amongst the most widely distributed nonhuman primates, show considerable phenotypic diversity, and have long been an important biomedical model for a variety of human diseases1 and in vaccine research2-4. They are particularly interesting for HIV/AIDS research as they are the most abundant natural hosts of simian immunodeficiency virus (SIV), a close relative of HIV. Here we present the first genome-wide survey of polymorphism in vervets, using sequencing data from 163 individuals sampled from across Africa and the Caribbean islands where vervets were introduced during the colonial era. We find high diversity, within and between taxa, and clear evidence that taxonomic divergence was reticulate rather than following a simple branching pattern. A scan for diversifying selection across vervet taxa yields gene enrichments much stronger than in similar studies on humans5. In particular, we report strong and highly polygenic selection signals affecting viral processes -- in line with recent evidence that proposes a driving role for viruses in protein evolution in mammals6. Furthermore, selection scores are highly elevated in genes whose human orthologs interact with HIV, and in genes that show a response to experimental SIV infection in vervet monkeys but not in rhesus macaques, suggesting that part of the signal reflects taxon-specific adaptation to SIV. Intriguingly, rather than affecting genes with antiviral and inflammatory-related functions7, selection in vervets appears to have primarily targeted genes involved in the transcriptional regulation of viruses, and in particular those that are harmful only under immunodeficiency, suggesting adaptation to living with SIV rather than defense against infection.

evolutionary biology↗