Neuroscience

Dissecting neural networks with Brainbow

Neurotropic viruses—which replicate in neurons and can cross synapses—are useful as neural circuit tracing tools. Card et al. combine this technology with the Brainbow approach to highlight neuronal connections within a larger network. They inserted the Brainbow cassette into the genome of an engineered pseudorabies virus, which resulted in the expression of either yellow or cyan fluorescent reporters in response to Cre recombinase–mediated recombination, allowing synaptic connections to be traced.

Card, J.P. et al. Proc. Natl. Acad. Sci. USA 108, 3377–3382 (2011).

Imaging

A label for electron cryotomography

Electron cryotomography allows cells, organelles and macromolecular assemblies to be imaged at high resolution in a near-native state. A major challenge, however, is the identification of cellular structures of interest. Wang et al. describe the use of a ferritin protein as a clonable fusion label for electron cryotomography. Ferritin consists of a protein shell with a central cavity that can be loaded with iron, providing an electron-dense tag for image contrast.

Wang, Q. et al. Structure 19, 147–154 (2011).

Genomics

A population-scale variation map

Mills et al. applied different methods, including paired-end mapping, depth-of-coverage analysis, split-read mapping and sequence assembly, to detect structural variants on a population scale. The resulting variant map encompasses deletions, insertions and tandem duplications, more than 50% of which could be mapped at base-pair resolution. This resource will be valuable for the understanding of the origin of variants, their genotyping in large cohorts and for disease-association studies.

Mills, R.E. et al. Nature 470, 59–65 (2011).

Sensors and probes

Oligodeoxyfluorosides for imaging

Guo et al. present oligodeoxyfluoroside (ODF) fluorophores, made up of a DNA backbone in which fluorophores replace the DNA bases; energy transfer between the fluorophores allows a wide variety of emission colors to be generated with a single excitation wavelength. The authors conjugated the ODF fluorophores to antibodies and showed that they could be used for multicolor cellular imaging.

Guo, J. et al. Proc. Natl. Acad. Sci. USA 108, 3493–3498 (2011).

Neuroscience

Optogenetics toolkit for primates

With optogenetics, light is harnessed to control specific neurons in the brain. Beyond basic neuroscience research applications, optogenetics has the potential to treat brain injury and disease. Diester et al. now present a set of optogenetics tools for experiments in nonhuman primates. They characterized the safety and efficiency of opsin expression in the rhesus monkey cortex. They also describe a fiber-optic device for making minimally invasive, repeated in vivo fluorescence measurements over time.

Diester, I. et al. Nat. Neurosci. 14, 387–397 (2011).