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982 Janelia Publications

Showing 1-10 of 982 results
07/12/16 | Forced chromatin looping raises fetal hemoglobin in adult sickle cells to higher levels than pharmacologic inducers.
Breda L, Motta I, Lourenco S, Gemmo C, Deng W, Rupon JW, Abdulmalik OY, Manwani D, Blobel GA, Rivella S
Blood. 2016 Jul 12:. doi: 10.1182/blood-2016-01-691089

Overcoming the silencing of the fetal γ-globin gene has been a long standing goal in the treatment of sickle cell disease (SCD). The major transcriptional enhancer of the β-globin locus, called LCR, dynamically interacts with the developmental stage-appropriate β-type globin genes via chromatin looping, a process requiring the protein Ldb1. In adult erythroid cells the LCR can be re-directed from the adult β- to the fetal γ-globin promoter by tethering Ldb1 to the human γ-globin promoter with custom designed zinc finger proteins (ZF-Ldb1), leading to reactivation of γ-globin gene expression. To compare this approach to pharmacological reactivation of fetal hemoglobin (HbF), hematopoietic cells from SCD patients were treated with a lentivirus expressing the ZF-Ldb1 or with chemical HbF inducers. The HbF increase in cells treated with ZF-Ldb1 was more than double of that observed with decitabine and pomalidomide; butyrate had an intermediate effect while tranylcypromine and hydroxyurea showed relatively low HbF reactivation. ZF-Ldb1 showed comparatively little toxicity, and reduced sickle Hb (HbS) synthesis as well as sickling of SCD erythroid cells under hypoxic conditions. The efficacy and low cytotoxicity of lentiviral-mediated ZF-Ldb1 gene transfer compared to the drug regimens support its therapeutic potential for the treatment of SCD.

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07/12/16 | Selective inhibition mediates the sequential recruitment of motor pools.
Zwart MF, Pulver SR, Truman JW, Fushiki A, Cardona A, Landgraf M
Neuron. 2016 Jul 12:. doi: 10.1016/j.neuron.2016.06.031

Locomotor systems generate diverse motor patterns to produce the movements underlying behavior, requiring that motor neurons be recruited at various phases of the locomotor cycle. Reciprocal inhibition produces alternating motor patterns; however, the mechanisms that generate other phasic relationships between intrasegmental motor pools are unknown. Here, we investigate one such motor pattern in the Drosophila larva, using a multidisciplinary approach including electrophysiology and ssTEM-based circuit reconstruction. We find that two motor pools that are sequentially recruited during locomotion have identical excitable properties. In contrast, they receive input from divergent premotor circuits. We find that this motor pattern is not orchestrated by differential excitatory input but by a GABAergic interneuron acting as a delay line to the later-recruited motor pool. Our findings show how a motor pattern is generated as a function of the modular organization of locomotor networks through segregation of inhibition, a potentially general mechanism for sequential motor patterns.

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07/11/16 | Evaluation of the Ser-His Dipeptide, a Putative Catalyst of Amide and Ester Hydrolysis.
MacDonald MJ, Lavis LD, Hilvert D, Gellman SH
Organic Letters. 2016 Jul 11:. doi: 10.1021/acs.orglett.6b01279

Efficient hydrolysis of amide bonds has long been a reaction of interest for organic chemists. The rate constants of proteases are unmatched by those of any synthetic catalyst. It has been proposed that a dipeptide containing serine and histidine is an effective catalyst of amide hydrolysis, based on an apparent ability to degrade a protein. The capacity of the Ser-His dipeptide to catalyze the hydrolysis of several discrete ester and amide substrates is investigated using previously described conditions. This dipeptide does not catalyze the hydrolysis of amide or unactivated ester groups in any of the substrates under the conditions evaluated.

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07/06/16 | A large fraction of neocortical myelin ensheathes axons of local inhibitory neurons.
Micheva KD, Wolman D, Mensh BD, Pax E, Buchanan J, Smith SJ, Bock DD
eLife. 2016 Jul 6:. doi: 10.7554/eLife.15784

Myelin is best known for its role in increasing the conduction velocity and metabolic efficiency of long-range excitatory axons. Accordingly, the myelin observed in neocortical gray matter is thought to mostly ensheath excitatory axons connecting to subcortical regions and distant cortical areas. Using independent analyses of light and electron microscopy data from mouse neocortex, we show that a surprisingly large fraction of cortical myelin (half the myelin in layer 2/3 and a quarter in layer 4) ensheathes axons of inhibitory neurons, specifically of parvalbumin-positive basket cells. This myelin differs significantly from that of excitatory axons in distribution and protein composition. Myelin on inhibitory axons is unlikely to meaningfully hasten the arrival of spikes at their pre-synaptic terminals, due to the patchy distribution and short path-lengths observed. Our results thus highlight the need for exploring alternative roles for myelin in neocortical circuits.

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07/04/16 | Protein-retention expansion microscopy of cells and tissues labeled using standard fluorescent proteins and antibodies.
Tillberg PW, Chen F, Piatkevich KD, Zhao Y, Yu CJay, English BP, Gao L, Martorell A, Suk H, Yoshida F, DeGennaro EM, Roossien DH, Gong G, Seneviratne U, Tannenbaum SR, Desimone R, Cai D, Boyden ES
Nature Biotechnology. 2016 Jul 4:. doi: 10.1038/nbt.3625

Expansion microscopy (ExM) enables imaging of preserved specimens with nanoscale precision on diffraction-limited instead of specialized super-resolution microscopes. ExM works by physically separating fluorescent probes after anchoring them to a swellable gel. The first ExM method did not result in the retention of native proteins in the gel and relied on custom-made reagents that are not widely available. Here we describe protein retention ExM (proExM), a variant of ExM in which proteins are anchored to the swellable gel, allowing the use of conventional fluorescently labeled antibodies and streptavidin, and fluorescent proteins. We validated and demonstrated the utility of proExM for multicolor super-resolution (∼70 nm) imaging of cells and mammalian tissues on conventional microscopes.

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06/27/16 | Falling apart.
Marvin JS, Looger LL
eLife. 2016;5:. doi: 10.7554/eLife.18203

Destabilized nanobodies can be used to deliver fluorescent proteins and enzymes to specific targets inside cells.

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06/18/16 | Macular telangiectasia type 1 managed with long-term aflibercept therapy.
Kovach JL, Hess HF, Rosenfeld PJ
Ophthalmic Surgery, Lasers and Imaging Retina. 2016 Jun;47(6):593-5. doi: 10.3928/23258160-20160601-14

A 60-year-old man diagnosed with macular telangiectasia type 1 (MacTel 1) was treated for 3 years with monthly aflibercept (Eylea; Regeneron, Tarrytown, NY) and serially imaged with spectral-domain optical coherence tomography. When administered monthly, aflibercept appeared to have a beneficial effect on macular edema secondary to MacTel 1. Visual acuity preservation despite minimal chronic macular edema could be attributed to the lack of significant photoreceptor disruption.

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06/20/16 | Doublesex regulates the connectivity of a neural circuit controlling Drosophila male courtship song.
Shirangi TR, Wong AM, Truman JW, Stern DL
Developmental Cell. 2016 Jun 20;37(6):533-44. doi: 10.1016/j.devcel.2016.05.012

It is unclear how regulatory genes establish neural circuits that compose sex-specific behaviors. The Drosophila melanogaster male courtship song provides a powerful model to study this problem. Courting males vibrate a wing to sing bouts of pulses and hums, called pulse and sine song, respectively. We report the discovery of male-specific thoracic interneurons—the TN1A neurons—that are required specifically for sine song. The TN1A neurons can drive the activity of a sex-non-specific wing motoneuron, hg1, which is also required for sine song. The male-specific connection between the TN1A neurons and the hg1 motoneuron is regulated by the sexual differentiation gene doublesex. We find that doublesex is required in the TN1A neurons during development to increase the density of the TN1A arbors that interact with dendrites of the hg1motoneuron. Our findings demonstrate how a sexual differentiation gene can build a sex-specific circuit motif by modulating neuronal arborization.

Doublesex-expressing TN1 neurons are necessary and sufficient for the male sine song•A subclass of TN1 neurons, TN1A, contributes to the sine song•TN1A neurons are functionally coupled to a sine song motoneuron, hg1Doublesex regulates the connectivity between the TN1A and hg1 neurons

It is unclear how developmental regulatory genes specify sex-specific behaviors. Shirangi et al. demonstrate that the Drosophila sexual differentiation gene doublesex encodes a sex-specific behavior—male song—by promoting the connectivity between the male-specific TN1A neurons and the sex-non-specific hg1 neurons, which are required for production of the song.

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06/17/16 | Complicating connectomes: Electrical coupling creates parallel pathways and degenerate circuit mechanisms.
Marder E, Gutierrez G, Nusbaum MP
Developmental Neurobiology. 2016 Jun 17:. doi: 10.1002/dneu.22410

Electrical coupling in circuits can produce non-intuitive circuit dynamics, as seen in both experimental work from the crustacean stomatogastric ganglion and in computational models inspired by the connectivity in this preparation. Ambiguities in interpreting the results of electrophysiological recordings can arise if sets of pre- or postsynaptic neurons are electrically coupled, or if the electrical coupling exhibits some specificity (e.g. rectifying, or voltage-dependent). Even in small circuits, electrical coupling can produce parallel pathways that can allow information to travel by monosynaptic and/or polysynaptic pathways. Consequently, similar changes in circuit dynamics can arise from entirely different underlying mechanisms. When neurons are coupled both chemically and electrically, modifying the relative strengths of the two interactions provides a mechanism for flexibility in circuit outputs. This, together with neuromodulation of gap junctions and coupled neurons is important both in developing and adult circuits. This article is protected by copyright. All rights reserved.

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06/17/16 | Complicating connectomes: Electrical coupling creates parallel pathways and degenerate circuit mechanisms.
Marder E, Gutierrez G, Nusbaum MP
Developmental Neurobiology. 2016 Jun 17:. doi: 10.1002/dneu.22410

Electrical coupling in circuits can produce non-intuitive circuit dynamics, as seen in both experimental work from the crustacean stomatogastric ganglion and in computational models inspired by the connectivity in this preparation. Ambiguities in interpreting the results of electrophysiological recordings can arise if sets of pre- or postsynaptic neurons are electrically coupled, or if the electrical coupling exhibits some specificity (e.g. rectifying, or voltage-dependent). Even in small circuits, electrical coupling can produce parallel pathways that can allow information to travel by monosynaptic and/or polysynaptic pathways. Consequently, similar changes in circuit dynamics can arise from entirely different underlying mechanisms. When neurons are coupled both chemically and electrically, modifying the relative strengths of the two interactions provides a mechanism for flexibility in circuit outputs. This, together with neuromodulation of gap junctions and coupled neurons is important both in developing and adult circuits. This article is protected by copyright. All rights reserved.

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