Faculty Bibliography

Somatodendritic dopamine (DA) release from midbrain DA neurons activates D2 autoreceptors on these cells to regulate their activity. However, the source of autoregulatory DA remains controversial. Here, we test the hypothesis that D2 autoreceptors on a given DA neuron in the substantia nigra pars compacta (SNc) are activated primarily by DA released from that same cell, rather than from its neighbors. Voltage-clamp recording allows monitoring of evoked D2-receptor-mediated inhibitory currents (D2ICs) in SNc DA neurons as an index of DA release. Single-cell application of antibodies to Na⁺ channels via the recording pipette decreases spontaneous activity of recorded neurons and attenuates evoked D2ICs; antibodies to SNAP-25, a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein, also decrease D2IC amplitude. Evoked D2ICs are nearly abolished by the light chain of botulinum neurotoxin A, which cleaves SNAP-25, whereas synaptically activated GABA_B-receptor-mediated currents are unaffected. Thus, somatodendritic DA release in the SNc autoinhibits the neuron that releases it.

Vagus nerve stimulation (VNS) suppresses inflammation and autoimmune diseases in preclinical and clinical studies. The underlying molecular, neurological, and anatomical mechanisms have been well characterized using acute electrophysiological stimulation of the vagus. However, there are several unanswered mechanistic questions about the effects of chronic VNS, which require solving numerous technical challenges for a long-term interface with the vagus in mice. Here, we describe a scalable model for long-term VNS in mice developed and validated in 4 research laboratories. We observed significant heart rate responses for at least 4 weeks in 60-90% of animals. Device implantation did not impair vagus-mediated reflexes. VNS using this implant significantly suppressed TNF levels in endotoxemia. Histological examination of implanted nerves revealed fibrotic encapsulation without axonal pathology. This model may be useful to study the physiology of the vagus and provides a tool to systematically investigate long-term VNS as therapy for chronic diseases modeled in mice.

Gamma oscillations are thought to coordinate the spike timing of functionally specialized neuronal ensembles across brain regions. To test this hypothesis, we optogenetically perturbed gamma spike timing in the rat medial (MEC) and lateral (LEC) entorhinal cortices and found impairments in spatial and object learning tasks, respectively. MEC and LEC were synchronized with the hippocampal dentate gyrus through high- and low-gamma-frequency rhythms, respectively, and engaged either granule cells or mossy cells and CA3 pyramidal cells in a task-dependent manner. Gamma perturbation disrupted the learning-induced assembly organization of target neurons. Our findings imply that pathway-specific gamma oscillations route task-relevant information between distinct neuronal subpopulations in the entorhinal-hippocampal circuit. We hypothesize that interregional gamma-time-scale spike coordination is a mechanism of neuronal communication.

PROBLEM/OBJECTIVE:Physician-scientists are individuals trained in both clinical practice and scientific research. Often, the goal of physician-scientist training is to address pressing questions in biomedical research. The established pathways to formally train such individuals are, mainly, MD-PhD programs and physician-scientist track residencies. Although graduates of these pathways are well equipped to be physician-scientists, numerous factors, including funding and length of training, discourage application to such programs and impede success rates. APPROACH/METHODS:To address some of the pressing challenges in training and retaining burgeoning physician-scientists, New York University Grossman School of Medicine formed the Accelerated MD-PhD-Residency Pathway in 2016. This pathway builds on the previously established accelerated three-year MD pathway to residency at the same institution. The Accelerated MD-PhD-Residency Pathway conditionally accepts MD-PhD trainees to a residency position at the same institution through the National Resident Matching Program. OUTCOMES/RESULTS:Since its inception, 2 students have joined the Accelerated MD-PhD-Residency Pathway, which provides protected research time in their chosen residency. The pathway reduces the time to earn an MD and PhD by one year and reduces the MD training phase to three years, reducing the cost and lowering socioeconomic barriers. Remaining at the same institution for residency allows for the growth of strong research collaborations and mentoring opportunities, which foster success. NEXT STEPS/UNASSIGNED:The authors and institutional leaders plan to increase the number of trainees that are accepted into the Accelerated MD-PhD-Residency Pathway and track the success of these students through residency and into practice to determine if the pathway is meeting its goal of increasing the number of practicing physician-scientists. The authors hope this model can serve as an example to leaders at other institutions who may wish to adopt this pathway for the training of their MD-PhD students.

OBJECTIVE:Familial Dysautonomia (FD) disease, lacks a useful biomarker for clinical monitoring. In this longitudinal study we characterized the structural changes in the macula, peripapillary and the optic nerve head (ONH) regions in subjects with FD. METHODS:Data was consecutively collected from subjects attending the FD clinic between 2012 and 2019. All subjects were imaged with spectral-domain Optical Coherence Tomography (OCT). Global and sectoral measurements of mean retinal nerve fiber layer (RNFL) and macular ganglion cell and inner plexiform layer (GCIPL) thickness, and ONH parameters of rim area, average cup-to-disc (C:D) ratio, and cup volume were used for the analysis. The best fit models (linear, quadratic and broken stick linear model) were used to describe the longitudinal change in each of the parameters. RESULTS:91 subjects (149 eyes) with FD of ages 5-56 years were included in the analysis. The rate of change for average RNFL and average GCIPL thicknesses were significant before reaching a plateau at the age of 26.2 for RNFL and 24.8 for GCIPL (- 0.861 µm/year (95% CI - 1.026, - 0.693) and - 0.553 µm/year (95% CI - 0.645, - 0.461), respectively). Significant linear rate of progression was noted for all ONH parameters, except for a subset of subjects (24%), with no cupping that did not show progression in any of the ONH parameters. CONCLUSIONS:The rapidly declining RNFL and GCIPL can explain the progressive visual impairment previously reported in these subjects. Among all structural parameters, ONH parameters might be most suitable for longitudinal follow-up, in eyes with a measurable cup.

BACKGROUND: Primary hyperoxaluria (PH) is a family of rare genetic disorders affecting 1-3 per 1 million persons globally. PH causes hepatic oxalate overproduction leading to increased urinary oxalate excretion, that can result in frequent kidney stone events, progression to end-stage kidney disease (ESKD) and then other systemic morbidities.
OBJECTIVE(S): To assess the burden of PH among patients and caregivers with respect to healthcare resource utilization (HRU), quality of life (QoL) and work productivity.
METHOD(S): An IRB-approved web survey was conducted among adults (>= 18 years) with PH, and caregivers of children (< 17 years) with PH in the US. Participants were asked about their or their child's medical care, HRU and QoL. The Kidney Disease Quality of Life (KDQOL-36TM: range 0-100, higher score = better QOL) and Work Productivity and Activity Impairment (WPAI: range 0-100%, higher score = more impairment) questionnaires were administered. Descriptive statistics summarized the responses.
RESULT(S): Patient sample (n = 21) comprised 7 adults (median age 42 years) and 14 children (median age 8 years). Patients' HRU consisted of visits to nephrologists (81%), urologists (67%) and ophthalmologists (10%). 33% visited the emergency room and 29% were hospitalized. Patients on dialysis (n = 5) spent a median of 24 hours per week receiving dialysis. PH complications included kidney stone events (95%), pain (71%, nearly all moderate-severe) and nephrocalcinosis (48%). 48% of all patients experienced PH-related anxiety. Adult patients' mean KDQOL-36TM domain scores (burden, symptoms/problems and effects of kidney disease) were 38 (SD = 23), 77 (SD = 23) and 65 (SD = 26), respectively. Employed adult patients (n = 4) reported 25% presenteeism (reduced productivity at work) on average based on the WPAI. Children missed a median of 15 hours/month of school due to their PH. Caregivers (n = 13) experienced moderate-severe anxiety about the possibility of future PH-related outcomes (i.e., kidney stones [54%], kidney disease progression [62%] and ESKD [62%]) for their child. Employed caregivers (n = 9) reported 28% presenteeism on average based on the WPAI.
CONCLUSION(S): This research quantifies the burden of PH in terms of HRU, QoL and productivity for patients and caregivers. Patients experienced considerable clinical sequalae associated with PH, such as kidney stones and pain, which appear to negatively affect these outcomes. Numerous clinician visits indicated an intensive level of care. Further, PH burden goes beyond the patient, as evidenced by caregiver burden, including anxiety and impact on work productivity

We review advances in understanding Purkinje cell (PC) complex spike (CS) physiology that suggest increased CS synchrony underlies syndromic essential tremor (ET). We searched PubMed for papers describing factors that affect CS synchrony or cerebellar circuits potentially related to tremor. Inferior olivary (IO) neurons are electrically coupled, with the degree of coupling controlled by excitatory and GABAergic inputs. Clusters of coupled IO neurons synchronize CSs within parasagittal bands via climbing fibers (Cfs). When motor cortex is stimulated in rats at varying frequencies, whisker movement occurs at ~10 Hz, correlated with synchronous CSs, indicating that the IO/CS oscillatory rhythm gates movement frequency. Intra-IO injection of the GABA_A receptor antagonist picrotoxin increases CS synchrony, increases whisker movement amplitude, and induces tremor. Harmaline and 5-HT_2a receptor activation also increase IO coupling and CS synchrony and induce tremor. The hotfoot17 mouse displays features found in ET brains, including cerebellar GluRδ2 deficiency and abnormal PC Cf innervation, with IO- and PC-dependent cerebellar oscillations and tremor likely due to enhanced CS synchrony. Heightened coupling within the IO oscillator leads, through its dynamic control of CS synchrony, to increased movement amplitude and, when sufficiently intense, action tremor. Increased CS synchrony secondary to aberrant Cf innervation of multiple PCs likely also underlies hotfoot17 tremor. Deep cerebellar nucleus (DCN) hypersynchrony may occur secondary to increased CS synchrony but might also occur from PC axonal terminal sprouting during partial PC loss. Through these combined mechanisms, increased CS/DCN synchrony may plausibly underlie syndromic ET.

Objective/UNASSIGNED:To test the hypothesis that many patients presenting with congenital insensitivity to pain have lesser known or unidentified mutations not captured by conventional genetic panels, we performed whole-exome sequencing in a cohort of well-characterized patients with a clinical diagnosis of congenital hereditary sensory and autonomic neuropathy with unrevealing conventional genetic testing. Methods/UNASSIGNED:We performed whole-exome sequencing (WES) in 13 patients with congenital impaired or absent sensation to pain and temperature with no identified molecular diagnosis from a conventional genetic panel. Patients underwent a comprehensive phenotypic assessment including autonomic function testing, and neurologic and ophthalmologic examinations. Results/UNASSIGNED:). Conclusions/UNASSIGNED:Our results expand the genetic landscape of congenital sensory and autonomic neuropathies. Further validation of some identified variants should confirm their pathogenicity. WES should be clinically considered to expedite diagnosis, reduce laboratory investigations, and guide enrollment in future gene therapy trials.