Faculty Bibliography

The hippocampal dentate gyrus is often viewed as a segregator of upstream information. Physiological support for such function has been hampered by a lack of well-defined characteristics that can identify granule cells and mossy cells. We developed an electrophysiology-based classification of dentate granule cells and mossy cells in mice that we validated by optogenetic tagging of mossy cells. Granule cells exhibited sparse firing, had a single place field, and showed only modest changes when the mouse was tested in different mazes in the same room. In contrast, mossy cells were more active, had multiple place fields and showed stronger remapping of place fields under the same conditions. Although the granule cell-mossy cell synapse was strong and facilitating, mossy cells rarely "inherited" place fields from single granule cells. Our findings suggest that the granule cells and mossy cells could be modulated separately and their joint action may be critical for pattern separation.

How type I and II interferons prevent periodic reemergence of latent pathogens in tissues of diverse cell types remains unknown. Using homogeneous neuron cultures latently infected with herpes simplex virus 1, we show that extrinsic type I or II interferon acts directly on neurons to induce unique gene expression signatures and inhibit the reactivation-specific burst of viral genome-wide transcription called phase I. Surprisingly, interferons suppressed reactivation only during a limited period early in phase I preceding productive virus growth. Sensitivity to type II interferon was selectively lost if viral ICP0, which normally accumulates later in phase I, was expressed before reactivation. Thus, interferons suppress reactivation by preventing initial expression of latent genomes but are ineffective once phase I viral proteins accumulate, limiting interferon action. This demonstrates that inducible reactivation from latency is only transiently sensitive to interferon. Moreover, it illustrates how latent pathogens escape host immune control to periodically replicate by rapidly deploying an interferon-resistant state.

Balance arises from the interplay of external forces acting on the body and internally generated movements. Many animal bodies are inherently unstable, necessitating corrective locomotion to maintain stability. Understanding how developing animals come to balance remains a challenge. Here we study the interplay among environment, sensation, and action as balance develops in larval zebrafish. We first model the physical forces that challenge underwater balance and experimentally confirm that larvae are subject to constant destabilization. Larvae propel in swim bouts that, we find, tend to stabilize the body. We confirm the relationship between locomotion and balance by changing larval body composition, exacerbating instability and eliciting more frequent swimming. Intriguingly, developing zebrafish come to control the initiation of locomotion, swimming preferentially when unstable, thus restoring preferred postures. To test the sufficiency of locomotor-driven stabilization and the developing control of movement timing, we incorporate both into a generative model of swimming. Simulated larvae recapitulate observed postures and movement timing across early development, but only when locomotor-driven stabilization and control of movement initiation are both utilized. We conclude the ability to move when unstable is the key developmental improvement to balance in larval zebrafish. Our work informs how emerging sensorimotor ability comes to impact how and why animals move when they do.

Chronic food restriction potentiates behavioral and cellular responses to drugs of abuse and D-1 dopamine receptor agonists administered systemically or locally in the nucleus accumbens (NAc). However, the alterations in NAc synaptic transmission underlying these effects are incompletely understood. AMPA receptor trafficking is a major mechanism for regulating synaptic strength, and previous studies have shown that both sucrose and d-amphetamine rapidly alter the abundance of AMPA receptor subunits in the NAc postsynaptic density (PSD) in a manner that differs between food-restricted and ad libitum fed rats. The present study examined whether food restriction, in the absence of reward stimulus challenge, alters AMPAR subunit abundance in the NAc PSD. Food restriction was found to increase surface expression and, specifically, PSD abundance, of GluA1 but not GluA2, suggesting synaptic incorporation of GluA2-lacking Ca2+-permeable AMPARs (CP-AMPARs). Naspm, an antagonist of CP-AMPARs, decreased the amplitude of evoked EPSCs in Nac shell, and blocked the enhanced locomotor response to local microinjection of the D-1 receptor agonist, SKF-82958, in food-restricted, but not ad libitum fed, subjects. Although microinjection of the D-2 receptor agonist, quinpirole, also induced greater locomotor activation in food-restricted than ad libitum fed rats, this effect was not decreased by Naspm. Taken together, the present findings are consistent with synaptic incorporation of CP-AMPARs in D-1 receptor expressing medium spiny neurons in NAc as a mechanistic underpinning of the enhanced responsiveness of food-restricted rats to natural rewards and drugs of abuse

A major feature of Alzheimer's disease (AD) is the loss of noradrenergic locus coeruleus (LC) projection neurons that mediate attention, memory, and arousal. However, the extent to which the LC projection system degenerates during the initial stages of AD is still under investigation. To address this question, we performed tyrosine hydroxylase (TH) immunohistochemistry and unbiased stereology of noradrenergic LC neurons in tissue harvested postmortem from subjects who died with a clinical diagnosis of no cognitive impairment (NCI), amnestic mild cognitive impairment (aMCI, a putative prodromal AD stage), or mild/moderate AD. Stereologic estimates of total LC neuron number revealed a 30% loss during the transition from NCI to aMCI, with an additional 25% loss of LC neurons in AD. Decreases in noradrenergic LC neuron number were significantly associated with worsening antemortem global cognitive function as well as poorer performance on neuropsychological tests of episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability. Reduced LC neuron numbers were also associated with increased postmortem neuropathology. To examine the cellular and molecular pathogenic processes underlying LC neurodegeneration in aMCI, we performed single population microarray analysis. These studies revealed significant reductions in select functional classes of mRNAs regulating mitochondrial respiration, redox homeostasis, and neuritic structural plasticity in neurons accessed from both aMCI and AD subjects compared to NCI. Specific gene expression levels within these functional classes were also associated with global cognitive deterioration and neuropathological burden. Taken together, these observations suggest that noradrenergic LC cellular and molecular pathology is a prominent feature of prodromal disease that contributes to cognitive dysfunction. Moreover, they lend support to a rational basis for targeting LC neuroprotection as a disease modifying strategy.

OBJECTIVE: To define the clinical features and biomarkers that predict which patients with pure autonomic failure will develop Parkinson disease, dementia with Lewy bodies, or multiple system atrophy. METHODS: One hundred patients who presented with pure autonomic failure were recruited at 5 medical centers in the U.S. Seventy-four patients agreed to be followed prospectively. Patients underwent clinical evaluations including neurological rating scales, sleep questionnaires, smell test, and sympathetic and parasympathetic cardiovascular autonomic function tests. RESULTS: At enrollment, patients were 68(12) years old [(median (interquartile range)] and had had autonomic failure for 5(7) years. Within 4-years of follow-up, 25 of 74 subjects (34%) developed dementia with Lewy bodies (in 13), Parkinson disease (in 6), or multiple system atrophy (in 6). The presence of probable REM sleep behavior disorder was strongly associated with the development of a manifest CNS synucleinopathy (odds ratio=7.1). Patients who phenoconverted to multiple system atrophy had younger age at onset of autonomic failure, severe bladder/bowel dysfunction, preserved olfaction, and a cardiac chronotrophic response upon tilt >10 beats per minute. Those who phenoconverted to Parkinson disease or dementia with Lewy bodies had decreased olfaction, a lesser chronotrophic response to tilt, and a longer duration of illness. The small group of patients retaining the pure autonomic failure phenotype had very low plasma norepinephrine levels, slow resting heart rate, no REM sleep behavior disorder, and preserved smell. INTERPRETATION: Patients presenting with pure autonomic failure are at high risk of phenoconverting to a manifest CNS synucleinopathy. Specific clinical features predict future diagnosis

Caregiver maltreatment induces vulnerability to later-life psychopathology. Clinical and preclinical evidence suggest changes in prefrontal and limbic circuitry underlie this susceptibility. We examined this question using a rat model of maternal maltreatment and methods translated from humans, resting-state functional magnetic resonance imaging (R-fMRI). Rat pups were reared by mothers provided with insufficient or abundant bedding for nest building from postnatal (PN) days 8 to 12 and underwent behavioral assessments of affect-related behaviors (forced swim, sucrose preference and social interaction) in adolescence (PN45) and early adulthood (PN60). R-fMRI sessions were conducted under light anesthesia at both ages. Offspring reared with insufficient bedding (that is, maltreated) displayed enduring negative affective behaviors. Amygdala-prefrontal cortex (PFC) functional connectivity increased significantly from adolescence to adulthood in controls, but not in maltreated animals. We computed the fractional amplitude of low-frequency fluctuations (fALFF), an index of intrinsic brain activity, and found that fALFF in medial prefrontal cortex and anterior cingulate cortex (MPFC/ACC) increased significantly with age in controls but remained unchanged in maltreated animals during adolescence and adulthood. We used a seed-based analysis to explore changes in functional connectivity between this region and the whole brain. Compared with controls, maltreated animals demonstrated reduced functional connectivity between MPFC/ACC and left caudate/putamen across both ages. Functional connectivity between MPFC/ACC and right caudate/putamen showed a group by age interaction: decreased in controls but increased in maltreated animals. These data suggest that maltreatment induces vulnerability to psychopathology and is associated with differential developmental trajectories of prefrontal and subcortical circuits underlying affect regulation.

Virus-mediated gene delivery shows promise for the treatment of chronic pain. However, viral vectors have cytotoxicity. To avoid toxicities and limitations of virus-mediated gene delivery, we developed a novel nonviral hybrid vector: HIV-1 Tat peptide sequence modified with histidine and cysteine residues combined with a cationic lipid. The vector has high transfection efficiency with little cytotoxicity in cancer cell lines including HSC-3 (human tongue squamous cell carcinoma) and exhibits differential expression in HSC-3 ( approximately 45-fold) relative to HGF-1 (human gingival fibroblasts) cells. We used the nonviral vector to transfect cancer with OPRM1, the mu-opioid receptor gene, as a novel method for treating cancer-induced pain. After HSC-3 cells were transfected with OPRM1, a cancer mouse model was created by inoculating the transfected HSC-3 cells into the hind paw or tongue of athymic mice to determine the analgesic potential of OPRM1 transfection. Mice with HSC-3 tumors expressing OPRM1 demonstrated significant antinociception compared with control mice. The effect was reversible with local naloxone administration. We quantified beta-endorphin secretion from HSC-3 cells and showed that HSC-3 cells transfected with OPRM1 secreted significantly more beta-endorphin than control HSC-3 cells. These findings indicate that nonviral delivery of the OPRM1 gene targeted to the cancer microenvironment has an analgesic effect in a preclinical cancer model, and nonviral gene delivery is a potential treatment for cancer pain.

Obsessive compulsive disorder (OCD) is substantially heritable, but few molecular genetic risk factors have been identified. Knockout mice lacking SLIT and NTRK-Like Family, Member 5 (SLITRK5) display OCD-like phenotypes including serotonin reuptake inhibitor-sensitive pathologic grooming, and corticostriatal dysfunction. Thus, mutations that impair SLITRK5 function may contribute to the genetic risk for OCD. We re-sequenced the protein-coding sequence of the human SLITRK5 gene (SLITRK5) in three hundred and seventy seven OCD subjects and compared rare non-synonymous mutations (RNMs) in that sample with similar mutations in the 1000 Genomes database. We also performed in silico assessments and in vitro functional synaptogenesis assays on the Slitrk5 mutations identified. We identified four RNM's among these OCD subjects. There were no significant differences in the prevalence or in silico effects of rare non-synonymous mutations in the OCD sample versus controls. Direct functional testing of recombinant SLITRK5 proteins found that all mutations identified in OCD subjects impaired synaptogenic activity whereas none of the pseudo-matched mutations identified in 1000 Genomes controls had significant effects on SLITRK5 function (Fisher's exact test P = 0.028). These results demonstrate that rare functional mutations in SLITRK5 contribute to the genetic risk for OCD in human populations. They also highlight the importance of biological characterization of allelic effects in understanding genotype-phenotype relationships as there were no statistical differences in overall prevalence or bioinformatically predicted effects of OCD case versus control mutations. Finally, these results converge with others to highlight the role of aberrant synaptic function in corticostriatal neurons in the pathophysiology of OCD.