Faculty Bibliography

The dragonbloodins are a pair of complex flavonoid trimers that have been isolated from the palm tree Daemonorops draco, one of the sources of the ancient resin known as "dragon's blood". We present a short synthesis that clarifies their relative configurations and sheds light on their origin in Nature. This synthesis features biomimetic cascade reactions that involve both ionic and radical intermediates. The biogenetic relationships between dracorhodin, the dracoflavans C, and the dragonbloodins A1 and A2 are discussed.

Regeneration of several organs involves adaptive reprogramming of progenitors, but the intrinsic capacity of the developing brain to replenish lost cells remains largely unknown. Here we found that the developing cerebellum has unappreciated progenitor plasticity, since it undergoes near full growth and functional recovery following acute depletion of granule cells, the most plentiful neuron population in the brain. We demonstrate that following postnatal ablation of granule cell progenitors, Nestin-expressing progenitors, specified during mid-embryogenesis to produce astroglia and interneurons, switch their fate and generate granule neurons in mice. Moreover, Hedgehog signaling in two Nestin-expressing progenitor populations is crucial not only for the compensatory replenishment of granule neurons but also for scaling interneuron and astrocyte numbers. Thus, we provide insights into the mechanisms underlying robustness of circuit formation in the cerebellum and speculate that adaptive reprogramming of progenitors in other brain regions plays a greater role than appreciated in developmental regeneration.

A concise, enantioselective synthesis of lycopladine A and carinatine A is presented. Our synthetic approach hinges on the recently developed mild carbocyclization of ynones to furnish the hydrindane core of the alkaloids. Their pyridine ring was efficiently installed using the Ciufolini method. Both heterocycles of carinatine A, a rare naturally occurring nitrone, were formed in a single operation.

The consolidation of context-dependent emotional memory requires communication between the hippocampus and the basolateral amygdala (BLA), but the mechanisms of this process are unknown. We recorded neuronal ensembles in the hippocampus and BLA while rats learned the location of an aversive air puff on a linear track, as well as during sleep before and after training. We found coordinated reactivations between the hippocampus and the BLA during non-REM sleep following training. These reactivations peaked during hippocampal sharp wave-ripples (SPW-Rs) and involved a subgroup of BLA cells positively modulated during hippocampal SPW-Rs. Notably, reactivation was stronger for the hippocampus-BLA correlation patterns representing the run direction that involved the air puff than for the 'safe' direction. These findings suggest that consolidation of contextual emotional memory occurs during ripple-reactivation of hippocampus-amygdala circuits.

The concurrent application of subtoxic doses of soluble oligomeric forms of human amyloid-beta (oAbeta) and Tau (oTau) proteins impairs memory and its electrophysiological surrogate long-term potentiation (LTP), effects that may be mediated by intra-neuronal oligomers uptake. Intrigued by these findings, we investigated whether oAbeta and oTau share a common mechanism when they impair memory and LTP in mice. We found that as already shown for oAbeta, also oTau can bind to amyloid precursor protein (APP). Moreover, efficient intra-neuronal uptake of oAbeta and oTau requires expression of APP. Finally, the toxic effect of both extracellular oAbeta and oTau on memory and LTP is dependent upon APP since APP-KO mice were resistant to oAbeta- and oTau-induced defects in spatial/associative memory and LTP. Thus, APP might serve as a common therapeutic target against Alzheimer's Disease (AD) and a host of other neurodegenerative diseases characterized by abnormal levels of Abeta and/or Tau.

The cystobactamids are a family of antibacterial natural products with unprecedented chemical scaffolds that are active against both Gram-positive and Gram-negative pathogens. Herein, we describe the first total synthesis of cystobactamid 919-2 from three fragments. Our convergent synthesis enabled both the confirmation of the correct structure and the determination of the absolute configuration of cystobactamid 919-2.

Venom peptide toxins such as conotoxins play a critical role in the characterization of nicotinic acetylcholine receptor (nAChR) structure and function and have potential as nervous system therapeutics as well. However, the lack of solved structures of conotoxins bound to nAChRs and the large size of these peptides are barriers to their computational docking and design. We addressed these challenges in the context of the alpha4beta2 nAChR, a widespread ligand-gated ion channel in the brain and a target for nicotine addiction therapy, and the 19-residue conotoxin alpha-GID that antagonizes it. We developed a docking algorithm, ToxDock, which used ensemble-docking and extensive conformational sampling to dock alpha-GID and its analogs to an alpha4beta2 nAChR homology model. Experimental testing demonstrated that a virtual screen with ToxDock correctly identified three bioactive alpha-GID mutants (alpha-GID[A10V], alpha-GID[V13I], and alpha-GID[V13Y]) and one inactive variant (alpha-GID[A10Q]). Two mutants, alpha-GID[A10V] and alpha-GID[V13Y], had substantially reduced potency at the human alpha7 nAChR relative to alpha-GID, a desirable feature for alpha-GID analogs. The general usefulness of the docking algorithm was highlighted by redocking of peptide toxins to two ion channels and a binding protein in which the peptide toxins successfully reverted back to near-native crystallographic poses after being perturbed. Our results demonstrate that ToxDock can overcome two fundamental challenges of docking large toxin peptides to ion channel homology models, as exemplified by the alpha-GID:alpha4beta2 nAChR complex, and is extendable to other toxin peptides and ion channels. ToxDock is freely available at rosie.rosettacommons.org/tox_dock.

Non-Cartesian magnetic resonance imaging (MRI) sequences have shown great promise for abdominal examination during free breathing, but break down in the presence of bulk patient motion (i.e. voluntary or involuntary patient movement resulting in translation, rotation or elastic deformations of the body). This work describes a data-consistency-driven image stabilization technique that detects and excludes bulk movements during data acquisition. Bulk motion is identified from changes in the signal intensity distribution across different elements of a multi-channel receive coil array. A short free induction decay signal is acquired after excitation and used as a measure to determine alterations in the load distribution. The technique has been implemented on a clinical MR scanner and evaluated in the abdomen. Six volunteers were scanned and two radiologists scored the reconstructions. To show the applicability to other body areas, additional neck and knee images were acquired. Data corrupted by bulk motion were successfully detected and excluded from image reconstruction. An overall increase in image sharpness and reduction of streaking and shine-through artifacts were seen in the volunteer study, as well as in the neck and knee scans. The proposed technique enables automatic real-time detection and exclusion of bulk motion during MR examinations without user interaction. It may help to improve the reliability of pediatric MRI examinations without the use of sedation.

Oral cancer patients report severe pain during function. Inflammation plays a role in the oral cancer microenvironment; however, the role of immune cells and associated secretion of inflammatory mediators in oral cancer pain has not been well defined. In this study, we utilized two oral cancer mouse models: a cell line supernatant injection model and the 4-nitroquinoline-1-oxide (4NQO) chemical carcinogenesis model. We used the two models to study changes in immune cell infiltrate and orofacial nociception associated with oral squamous cell carcinoma (oSCC). Oral cancer cell line supernatant inoculation and 4NQO-induced oSCC resulted in functional allodynia and neuronal sensitization of trigeminal tongue afferent neurons. While the infiltration of immune cells is a prominent component of both oral cancer models, our use of immune-deficient mice demonstrated that oral cancer-induced nociception was not dependent on the inflammatory component. Furthermore, the inflammatory cytokine, tumor necrosis factor alpha (TNFa), was identified in high concentration in oral cancer cell line supernatant and in the tongue tissue of 4NQO-treated mice with oSCC. Inhibition of TNFa signaling abolished oral cancer cell line supernatant-evoked functional allodynia and disrupted T cell infiltration. With these data, we identified TNFa as a prominent mediator in oral cancer-induced nociception and inflammation highlighting the need for further investigation in neural-immune communication in cancer pain.

Deficits in cost-benefit decision making, as assessed in the Iowa Gambling Task (IGT), are commonly observed in neuropsychiatric disorders such as addiction. There is considerable variation in the maximisation of rewards on such tasks, both in the general population and in rodent models, suggesting individual differences in decision making may represent a key endophenotype for vulnerability to neuropsychiatric disorders. Increasing evidence suggests that the insular cortex, which is involved in interoception and emotional processes in humans, may be a key neural locus in the control of decision making processes. However, the extent to which the insula contributes to individual differences in cost-benefit decision making remains unknown. Using male Sprague-Dawley rats we first assessed individual differences in the performance over the course of a single session on a rodent analogue of the IGT (rGT). Rats were matched for their ability to maximise reward and received bilateral excitotoxic or sham lesions of the anterior insula cortex (AIC). Animals were subsequently challenged on a second rGT session with altered contingencies. Finally, animals were also assessed for instrumental conditioning and reversal learning. AIC lesions produced bidirectional alterations on rGT performance; rats that had performed optimally prior to surgery subsequently showed impairments, and animals that had performed poorly showed improvements in comparison to sham operated controls. These bidirectional effects were not attributable to alterations in behavioural flexibility or in motivation. These data suggest that the recruitment of the AIC during decision making may be state-dependent and help guide response selection toward subjectively favourable options.