Inheritance of a Phenotypically Neutral Epimutation Evokes Gene Silencing in Later Generations.

Small RNAs trigger the formation of epialleles that are silenced across generations. Consequently, RNA-directed epimutagenesis is associated with persistent gene repression. Here, we demonstrate that small interfering RNA-induced epimutations in fission yeast are still inherited even when the silenced gene is reactivated, and descendants can reinstate the silencing phenotype that only occurred in their ancestors.

Dicer and Hsp104 function in a negative feedback loop to confer robustness to environmental stress.

Epigenetic mechanisms can be influenced by environmental cues and thus evoke phenotypic variation. This plasticity can be advantageous for adaptation but also detrimental if not tightly controlled. Although having attracted considerable interest, it remains largely unknown if and how environmental cues such as temperature trigger epigenetic alterations.

Projection neuron circuits resolved using correlative array tomography.

Assessment of three-dimensional morphological structure and synaptic connectivity is essential for a comprehensive understanding of neural processes controlling behavior. Different microscopy approaches have been proposed based on light microcopy (LM), electron microscopy (EM), or a combination of both. Correlative array tomography (CAT) is a technique in which arrays of ultrathin serial sections are repeatedly stained with fluorescent antibodies against synaptic molecules and neurotransmitters and imaged with LM and EM (Micheva and Smith, 2007).

Correlative microscopy of densely labeled projection neurons using neural tracers.

Three-dimensional morphological information about neural microcircuits is of high interest in neuroscience, but acquiring this information remains challenging. A promising new correlative technique for brain imaging is array tomography (Micheva and Smith, 2007), in which series of ultrathin brain sections are treated with fluorescent antibodies against neurotransmitters and synaptic proteins. Treated sections are repeatedly imaged in the fluorescence light microscope (FLM) and then in the electron microscope (EM).