Microscopy (2): studying molecular motors

An article in Cell by recent Molecular and Cell Biology Ph.D. graduate Susan Tran and coworkers demonstrates the power of single particle microscopy in combination with Drosophila genetics in studying molecular motors. Studying lipid droplet movement in embryos, they show that multiple motors are attached to droplets in vivo. Surprisingly, having multiple motors per droplet in vivo doesn’t result in higher velocities or distances traveled.

How long does it take the brain to access short-term memory?

A recent paper in Neuroimage by Brandeis Neuroscience Ph. D. program alumnus Yigal Agam, Professor Robert Sekuler and coworkers attempts to answer the question. To identify the earliest neural signs of recognition memory, they used event related potentials collected from human observers engaged in a visual short term memory task.  Their results point to an initial feed-forward interaction that underlies comparisons between what is being current seen and what has been stored in memory.  The locus of these earliest recognition-related potentials is consistent with the idea that visual areas of the brain contribute to temporary storage of visual information for use in ongoing tasks. This study provides a first look into early neural activity that supports the processing of visual information during short-term memory.

Actin "pointers" for EM labeling

Single particle electron microscopy reconstruction can be a powerful tool for determining the structure of large protein complexes. One limitation of the technique is the difficulty in coming up with specific labels for the protein that can be visualized with EM. In a new paper in RNA, postdoc Beth Stroupe and coworkers show that the use of the actin-nucleating protein Spire as a cloneable tag allows them to nucleate actin filaments that then “point” to the location of the tag in the complex seen in EM, and applied the technique to their studies of the C complex spliceosome.

How regions of the brain get their specificity

The cortex is divided into functionally distinct regions, and the layers of the visual cortex are a classic example. But how much do the intrinsic electrical properties of a particular neuron type vary from region to region? In a recent paper in J. Neurosci., Brandeis Neuroscience graduate students Mark Miller and Ben Okaty together with Prof. Sacha Nelson found a new region-specific firing type in Layer 5 pyramidal neurons. They argue that features as basic as membrane properties can be region-specific, and that this regional specialization of circuitry contributes to the determination of the region’s functional specialization.

Cell cycle checkpoint from the stringent response

E.coli cells exiting the stringent response

E.coli cells exiting the stringent response

The stringent response in E.coli is a response to nutrient (typically amino acid) starvation and is characterized by the accumulation of the small molecular regulator ppGpp, and a global response in transcriptional regulation.  In a new paper in PLoS Genetics, Daniel Ferullo and Susan Lovett examine chromosome segregation during the stringent respons and discuss what appears to be a novel G1-like cell cycle checkpoint in bacteria that occurs as the result.

Structural diversity of amyloid fibrils

Amyloid fibrils are associated with Alzheimer’s disease. In a recent study published in J. Mol. Biol., Nikolaus Grigorieff and coworkers used electron cyro-microscopy to study these structures and show that these fibrils coexisting in solution can be extremely polymorphic.

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