Research

The primary research interest in my lab is to understand the function and the regulation of dopaminergic neurons, with a particular focus at the synapse and the mechanisms of its dysregulation in disease conditions.

Dopaminergic signaling modulates a multitude of human behaviors including body movements, reward and addiction, as well as motivational behaviors. Loss of dopamine neurons in the Substantia Nigra leads to Parkinson’s disease (PD), yet questions remain as to why dopamine neurons are more vulnerable. We aim to understand dopamine neurons by analyzing known genetic PD risk factors and their signaling pathways both in vitro and in vivo at different parts of the brain.

Supported by an NINDS R01 grant, we are currently investigating the role of the Synj1 gene in deregulating the basal ganglia function using mouse models. SYNJ1, also known as PARK20, is one of the synaptic genes associated with Parkinsonism. Indeed, both human and mouse studies suggests that partial loss of Synj1 function (either via disease-linked missense mutation or heterozygous deletion) leads to abnormal motor functions and an impaired dopaminergic pathway. The mechanism underlying dopaminergic dystrophy due to Synj1 deficiency is not well understood. We use transgenic mouse models, primary dopamine neuron culture, quantitative imaging, as well as biochemical, behavioral, and pathological analyses to understand cell type, brain region-specific signatures, and vulnerabilities relevant to dopaminergic dysregulation in various conditions of Synj1 deficiency.

Additionally, we are interested in exploring the relationship between dopamine vulnerability and dopamine-dependent addiction mechanisms. Anatomically, the dorsostriatal dopamine pathway regulates the motor function and the mesolimbic (medioventral) pathway is involved in addiction. However, substantial crosstalk has been reported for the two dopaminergic pathways. Epidemiological studies show that nicotine intake via tobacco smoking significantly reduces the risk of PD. We hope to use the Synj1 mouse as a handle to address the interesting crosstalk in dopamine signaling. We also recently engineered a novel optical sensor, DAT-pHluorin, that is capable of reporting DAT trafficking in real time in live neurons and in awake behaving mice (through collaboration)! DAT is an essential molecule that mediates dopamine reuptake to terminate dopamine signaling in the brain. DAT is the target of various psychoactive substances and it also partners with multiple PD genes during pathogenesis. We are excited to exploit this new tool to examine molecular mechanisms underlying substance use disorder as well as PD. 

The main research strategy of the lab is microscopy. We utilize various optical tools, including genetically encoded calcium indicators, pH sensors and protein activity reporters to investigate the biology and pathophysiology of the synapse.

There are two imaging rigs in the lab.

One of them is suited for low light high-speed quantitative imaging. The system is built on a Nikon Ti2-E inverted microscope with a Ti2-S-SE-E motorized stage and linear encoder and perfect focus system (PFS). Attached to the optical port of the microscope body is the Andor iXon Life 897 EMCCD camera. We use SPECTA X (from Lumencor) as the high-speed switchable illumination source with the capacity of simultaneous imaging of multiple fluorophores. There are currently six built-in light beams at different wavelengths including 395 nm, 430 nm, 470 nm, 505 nm, 561 nm, 640 nm for versatile applications.

The other one a Nikon CREST spinning disk confocal microscope for higher resolution imaging. The Celesta light engine contains 7 LED laser lines which covers the spectrum from UV to far-red (750 nm) imaging. Attached to the optical port of the microscope body is a highly sensitive Photometrics Prime 95B-25MM back-illuminated cMOS camera.

For both workstations, field electrical stimulation can be delivered via Accupulser A310 and monitored by the oscilloscope. The temperature of the experiment can be adjusted at the objective by a temperature control system from the Warner Instrument/Tokai HIT. There are eight gravity perfusion lines controlled by the ValveLink 8.2 system. The entire work station is run by the NIS-Elements software.