A comprehensive cellular map of the human thymus across a lifespan is presented in Science this week, marking the latest offering from the Human Cell Atlas initiative. A team led by Wellcome Sanger Institute scientists use single-cell RNA sequencing to create a cell census of the human thymus across the lifespan and to reconstruct T cell differentiation trajectories and T cell receptor recombination kinetics. The analysis reveals "the complexity of cell types constituting the thymus, as well as the breadth of interactions between stromal cells and innate immune cells to coordinate thymic development to support T cell differentiation," the study's authors write. GenomeWeb has more on this, here.
By applying a novel computation method to ancient genetic data, scientists from the University of Utah find support for the theory that ancestors of two archaic populations, Neanderthals and Denisovans — called Neandersovans — interbred with members of a "superarchaic" population that separated from other humans about 2 million years ago. The scientists considered eight models with genetic combinations that may have resulted from interbreeding between early hominins, analyzing the data with software that uses counts of nucleotide site patterns to estimate the history of population size, subdivision, and gene flow. Their findings, which appear in Science Advances, point to interbreeding between Neandersovans and superarchaics early in the middle Pleistocene, shortly after expanding into Eurasia. "This is the earliest known admixture between hominin populations," the authors write. "Furthermore, the two populations involved were more distantly related than any pair of human populations previously known to interbreed." GenomeWeb also covers this, here.