Commentary: Anxiety- and Depression-like States Lead to Pronounced Olfactory Deficits and Impaired Adult Neurogenesis in Mice

A commentary on: Anxiety- and Depression-like States Lead to Pronounced Olfactory Deficits and Impaired Adult Neurogenesis in Mice by Siopi, E., Denizet, M., Gabellec, M. M., de Chaumont, F., Olivo-Marin, J. C., Guilloux, J. P., et al. (2016). J. Neurosci. 36, 518–531. doi: 10.1523/JNEUROSCI.2817-15.201

Direct evidence for sequence-dependent attraction between double-stranded DNA controlled by methylation

Although proteins mediate highly ordered DNA organization in vivo, theoretical studies suggest that homologous DNA duplexes can preferentially associate with one another even in the absence of proteins. Here we combine molecular dynamics simulations with single-molecule fluorescence resonance energy transfer experiments to examine the interactions between duplex DNA in the presence of spermine, a biological polycation. We find that AT-rich DNA duplexes associate more strongly than GC-rich duplexes, regardless of the sequence homology. Methyl groups of thymine acts as a steric block, relocating spermine from major grooves to interhelical regions, thereby increasing DNA-DNA attraction. Indeed, methylation of cytosines makes attraction between GC-rich DNA as strong as that between AT-rich DNA. Recent genome-wide chromosome organization studies showed that remote contact frequencies are higher for AT-rich and methylated DNA, suggesting that direct DNA-DNA interactions that we report here may play a role in the chromosome organization and gene regulationopen

Single Molecule Imaging in Live Embryos Using Lattice Light-Sheet Microscopy

In the past decade, live-cell single molecule imaging studies have provided unique insights on how DNA-binding molecules such as transcription factors explore the nuclear environment to search for and bind to their targets. However, due to technological limitations, single molecule experiments in living specimens have largely been limited to monolayer cell cultures. Lattice light-sheet microscopy overcomes these limitations and has now enabled single molecule imaging within thicker specimens such as embryos. Here we describe a general procedure to perform single molecule imaging in living Drosophila melanogaster embryos using lattice light-sheet microscopy. This protocol allows direct observation of both transcription factor diffusion and binding dynamics. Finally, we illustrate how this Drosophila protocol can be extended to other thick samples using single molecule imaging in live mouse embryos as an example

Spatially encoded fast single-molecule fluorescence spectroscopy with full field-of-view

Abstract We report a simple single-molecule fluorescence imaging method that increases the temporal resolution of any type of array detector by >5-fold with full field-of-view. We spread single-molecule spots to adjacent pixels by rotating a mirror in the detection path during the exposure time of a single frame, which encodes temporal information into the spatial domain. Our approach allowed us to monitor fast blinking of an organic dye, the dissociation kinetics of very short DNA and conformational changes of biomolecules with much improved temporal resolution than the conventional method. Our technique is useful when a large field-of-view is required, for example, in the case of weakly interacting biomolecules or cellular imaging