News and Events from and for the Division of Science, Brandeis University
IMAGE: BMXIMAGE (from Forbes India)
Forbes India recently named Brandeis post-doc alumna Prerna Sharma as one of India’s “30 under 30”. Sharma, who worked in Prof. Zvonimir Dogic’s group in Physics, is currently an Assistant Professor at the Indian Institute of Science (IISc), Bangalore.
Read the original at Prerna Sharma: The scientist of small things, or perhaps her 2014 Nature paper on Hierarchical organization of chiral rafts in colloidal membranes
In a new paper in eLIFE, a team spearheaded by Brandeis postdocs David Doroquez and Cristina Berciu provide a strikingly detailed look at key structures called cilia on neurons involved in sensory perception in the nematode C. elegans. Primary cilia are the antenna-like structures onsensory neurons that gather information about the animal’s environment, such as chemicals, temperature, humidity, and touch. The genetic tools available to manipulate individual, identifiable neurons in C. elegans make worms an excellent model organism to study the assembly and function of cilia. This study requires a description of the structure of the cilia and their immediate surrounding glial support cells, and this new paper, a collaboration of the Sengupta and Nicastro labs, provides high-resolution 3D models showing how diverse and specialized these structures are.
A bouquet of sensory antennae. The 3D ultrastructure of all sensory cilia
and other neuronal projections in the head of the soil roundworm C.
elegans have been reconstructed using serial section transmission electron
microscopy. Shown are 3D isosurface-rendering models emerging from a
transmission electron microscopic cross-section of the worm.
The key techniques in this study were serial section transmission electron microscopy and electron tomography, with structures well-preserved by high-pressure freezing and freeze-substitution. With these techniques, the authors achieved the first high-resolution 3D reconstructions of 50/60 cilia from C. elegans. They describe several previously uncharacterized features — for example, there are distinct types of branching patterns – in one, the two cilia originate from independent basal bodies (as previously seen in Chlamydomonas). In the second, the cilia branch after the basal transition zone, the ciliary gatekeeper region. In the latter case, this basically means that whatever is needed for the cilia to branch has to be transported through the transition zone, suggest there might be novel mechanisms of ciliary protein trafficking. In a third pattern, the branching occurs proximally before the transition zone, and represent therefore dendritic microvilli, rather than ciliary branching. The study also showed different organizations of microtubules in different cilia types and vesicles in regions of the cilia which have never been seen before, again pointing to new mechanisms of protein transport. They also describe new cilia-glial interactions, which might suggest that cilia and glia talk to each other.
For more about these structures (with lots of pretty pictures and movies), see:
How do children learn to play instruments and speak languages so much easier than adults, and why does brain damage result in worse outcomes in the mature brain vs. the young brain? These questions are central to the study of how “critical periods” are regulated in the brain.
Electron micrograph from a single 70 nm cross-section through a fast-spiking parvalbumin-containing (gold labeling = white dots) presynaptic terminal forming a synapse (red dots) with a pyramidal soma. Original colors are inverted, contours have been raised and membranous structures are highlighted in aqua for ease of visualization. Presynaptic vesicles (colored ovals) within perisomatic fast spiking terminals mostly cluster within ∼200 nm of the synapse, with a few close enough (≤2 nm) to be deemed docked.
Critical periods in brain development define temporal windows when neuronal physiology and anatomy are most sensitive to changes in sensory input or experience (e.g. sound, touch, light, etc.). The maturation of inhibitory cells that release the neurotransmitter GABA, especially a subset called fast-spiking (FS) interneurons, is thought to gate this period of neuronal ‘plasticity’ in the mammalian primary visual cortex. However, it has remained unclear what aspects of FS cell development are important for permitting this period of neuronal malleability in the visual cortex. A new paper in Journal of Neuroscience from the Turrigiano lab addresses the question.
To explore how FS cell development might be linked to critical period plasticity, Brandeis postdoc Marc Nahmani and Professor Gina Turrigiano employed a well-established assay for cortical plasticity in visual cortex called monocular deprivation (MD), and measured FS cell connections using confocal and electron microscopy, as well as optogenetic stimulation of the FS cell population (i.e. shining light onto FS cells possessing light-gated channels to make them fire action potentials).
Following up on previous work from the Turrigiano lab (Maffei et al., 2006), they found that MD induces a coordinated increase in FS interneuron to pyramidal cell (the major excitatory output cells of the cortex) pre- and postsynaptic strength. These changes occur if MD is performed during, but not before the critical period in visual cortex, suggesting they may play a role in gating this period of heightened neuronal plasticity. Future studies are aimed at determining the timeline for these changes across the extent of the critical period in visual cortex.
see: Nahmani M, Turrigiano GG (2014) Deprivation-Induced Strengthening of Presynaptic and Postsynaptic Inhibitory Transmission in Layer 4 of Visual Cortex during the Critical Period. Journal of Neuroscience 34:2571-2582.
If you remember your (bio-)physical chemistry, you’ll remember that most proteins are temperature sensitive. But which ones acts as the sensors that drive behavior in higher organisms? The Garrity Lab at Brandeis has been working on thermosensation in Drosophila, and previous work has implicated the channel protein TRPA1 as a key mediator of temperature preference and thermotaxis, In a new paper in Nature, members of the Garrity lab working in collaboration with the Griffith and Theobald have have identified another protein, GR28B(D), a member of the family of gustatory receptor proteins, as another behaviorally important temperature sensor, involved in rapid avoidance of high temperatures. Authors on the paper include postdocs Lina Ni (lead author) and Peter Bronk, grad students April Lowell (Mol. Cell Biology) and Vincent Panzano (PhD ’13, Neuroscience), undergraduate Juliette Flam ’12, and technician Elaine Chang ’08.
Assistant Professor of Biology Avital Rodal has received a grant from the Blazeman Foundation to study the traffic of growth signals in neurons in the animal models of ALS (Amyotrophic Lateral Sclerosis). ALS, commonly known as ‘Lou Gehrig’s disease’, is a neurodegenerative disease that causes the loss of motor neurons. The Blazeman Foundation is a non-profit organization working to increase the awareness about this terminal disease and to support research towards finding treatments. Funding to the Rodal lab has enabled creation of the Blazeman Foundation Postdoctoral Fellowship for ALS Research, awarded to Mugdha Deshpande, Ph.D., who will use live imaging to examine and manipulate membrane traffic in fruit fly models of ALS, and who will also work with Dr. Suzanne Paradis to translate her findings to mammalian ALS models.
You can read more at BrandeisNOW.
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