In Nature Biotechnology this week, a team led by University of California, San Diego, researchers report on a new system for massively parallel polymerase cloning and genome sequencing of single cells. Despite the benefits of single-cell genome sequencing, the bias in amplifying genetic material from a single cell has been challenging, they note. To overcome this hurdle, the scientists developed a microwell displacement amplification system, or MIDAS — a massively parallel polymerase cloning method in which single cells are randomly distributed into hundreds to thousands of nanoliter wells and their genetic material is simultaneously amplified for shotgun sequencing. MIDAS reduces amplification bias because polymerase cloning occurs in physically separated, nanoliter-scale reactors, facilitating the de novo assembly of near-complete microbial genomes from single Escherichia coli cells. It also allowed the researchers to detect single-copy number changes in primary human adult neurons at 1 megabase to 2 megabase resolution.
In Sequence has more on this study here.
Meanwhile, in Nature Methods, researchers from Stanford University and elsewhere describe a new method to measure real-time changes in translation rates in single human or mouse cells. The approach involves conjugating translation regulatory motifs to sequences encoding a nuclear-targeted fluorescent protein and a controllable destabilization domain. With the method, the scientists were able to show that individual cells undergo marked fluctuations in the translation rate of mRNAs whose 5' terminal oligopyrimidine motif regulates the synthesis of ribosomal proteins. They also demonstrated that small reductions in amino acid levels signal through different mTOR-dependent pathways to control terminal oligopyrimidine mRNA translation, whereas larger reductions in amino acid levels control translation through eiF2A.