Biology subjects

Lee, J. O.

Publications and source records attributed to Lee, J. O..

5 recordsLinked to original sources

bioRxiv2026

Split intein vectors permit oversize FLIM-FRET biosensor neuronal expression

Adeno-associated virus (AAV) packaging limits constrain the design, performance, and in vivo application of genetically encoded biosensors. We developed a split intein-mediated reconstitution strategy enabling modular delivery and reassembly of oversized fluorescence lifetime-based biosensors. Using this platform, we engineered an oversized cAMP sensor compatible with one-photon fluorescence lifetime measurements, enabling monitoring of intracellular signaling dynamics in distinct neuronal subtypes in freely behaving mice.

bioengineering↗

bioRxiv2023

Motor cortex somatostatin interneurons adaptively shape the structure of motor sequences

The brain can flexibly reorganize the structure of action sequence, or motor programs, to efficiently reach positive outcomes. These behavioral adaptations are primarily driven by reinforcement learning, leading to structural and kinematic modifications of consolidated motor programs. While the motor cortex is recognized as a crucial neural substrate for adaptive motor control and skill learning, the mechanisms by which cortical microcircuits actively fine-tune the timing and structure of action sequences, enabling organisms to adaptively maintain motor efficiency across varying task demands, remain unclear. Here, we found that the calcium activity of somatostatin (SST) interneurons (INs) in the primary motor cortex (M1) exhibits highly action-locked and synchronized calcium responses during the acquisition of a single lever-press task in freely moving mice. This neural representation contrasts with the sequential activation of pyramidal (PYR) neurons during the same task. After extended training with a consistent schedule and subsequent motor consolidation, M1 SST IN activity was no longer related to action execution. However, when the training schedule was progressively updated, leading mice to adapt their motor programs for more time-constrained, rapid action sequences, the action-related SST IN activity redistributed and did not decrease. Notably, this redistributed calcium activity of M1 SST INs correlated with structural modulation of ongoing action sequences. We identified two distinct neural activity patterns among non-overlapping SST IN populations: one encoding the initiation of action sequences and the other encoding trial-by-trial structural changes during the execution of complex action sequences. Moreover, inhibition of SST INs disrupted temporal structure of action sequences and decreased the efficiency of motor program execution. These findings highlight the unexpected role of M1 SST interneurons in actively refining motor programs into more efficient and task-specific structures. HIGHLIGHTSO_LIActivation of somatostatin (SST) interneurons in the primary motor cortex (M1) correlates with learning new motor actions and execution of complex motor programs. C_LIO_LIDistinct activity patterns of M1 SST interneurons actively encode the initiation and temporal structure of complex action sequences on a trial-by-trial basis C_LIO_LIInhibition of SST interneuron activity leads to inefficient execution of complex motor programs, with effects dependent on task specificity. C_LI

neuroscience↗

bioRxiv2022

Sub-second striatal dopamine dynamics assessed by simultaneous fast-scan cyclic voltammetry and fluorescence biosensor

Dopamine produces neuromodulation throughout the basal ganglia, cortex and other brain regions, and is implicated in movement control, neural mechanisms of reward and actions of misused substances. The efferent projections of dopaminergic neurons with somata in the substantia nigra pars compacta and ventral tegmental area strongly innervate different striatal subregions. While much is known about the function of these neurons, there is a relative deficiency of information about in vivo dopamine dynamics in the nigrostriatal projections, especially those to the dorsolateral striatum (DLS). In past studies, subsecond dopamine changes were measured predominantly with fast-scan cyclic voltammetry (FSCV) both in brain slices and in vivo. However, traditional FSCV has limitations in discriminating among catecholamines, and cannot be used for simultaneous measurement of both slow and fast/phasic dopamine changes. In addition, FSCV has been most useful for measuring dopamine in the ventral striatum in vivo with less utility for measurement in dorsolateral striatum. The development of genetically encoded dopamine sensors has provided a new approach to measuring slow and fast dopamine dynamics both in brain slices and in vivo, raising the hope of more facile measurement of in vivo dopamine measurements, including in areas where measurement was previously difficult with FSCV. To this end, we first evaluated dLight photometry in brain slices with simultaneous FSCV. We found that both techniques yielded comparable findings. However, differences were noted in responses to dopamine transporter inhibitors, including cocaine. We then used in vivo fiber photometry with dLight to examine responses to cocaine in DLS and compared responses during Pavlovian conditioning in DLS to two other striatal subregions. These experiments show that dopamine increases are readily detectable in DLS and provide new information about dopamine transient kinetics and slowly developing signaling during conditioning. Overall, our findings indicate that dLight photometry is well suited to measuring dopamine dynamics in a striatal region of great interest where such measurements were difficult previously.

neuroscience↗

bioRxiv2020

Stress and behavioral correlates in the head-fixed method

Head-fixation of awake rodents is a method that allows for sophisticated investigation and manipulation of neural circuits in vivo, that would otherwise be impossible in completely freely moving animals. However, while it is known that head-fixation induces stress, its scale and habituation dynamics remain unclear. Thus, interpretation of physiological and behavioral experiments would greatly benefit from the characterization of the stress response. In our study, we used the Mobile HomeCage system (Neurotar, Finland) where animals are head-fixed to an aluminum frame, but otherwise freely moving in an ultralight carbon container floating above an air-dispensing base. To better understand this experimental environment, we analyzed locomotion and stress during an extended habituation protocol. For 25 consecutive days, mice were prepared as they would be for recording experiments, i.e. head-fixed while standing on the air-lifted platform for 2 hours per day. Throughout 25 days, blood samples were taken periodically from the tail vein to measure variation in the stress-related hormone, corticosterone. These data were compared and contrasted with behavioral data including locomotion during the 2-hours head-fixed habituation sessions and several classical behavioral measurements known to be affected by chronic mild stress.

physiology↗

bioRxiv2018

Meteorin-like (Metrnl) adipomyokine improves glucose tolerance in type 2 diabetes via AMPK pathway

Meteorin-like (metrnl) is a recently identified adipomyokine that has beneficial effects on glucose metabolism. However, its underlying mechanism of action is not completely understood. In this study, we have shown that a level of metrnl increase in vitro under electrical-pulse-stimulation (EPS) and in vivo in exercise mice, suggesting that metrnl is an exercise-induced myokine. In addition, metrnl increases glucose uptake through the calcium-dependent AMPK pathway. Metrnl also increases the phosphorylation of HDAC5, a transcriptional repressor of GLUT4, in an AMPK-dependent manner. Phosphorylated HDAC5 interacts with 14-3-3 proteins and sequesters them in the cytoplasm, resulting in the activation of GLUT4 transcription. The intraperitoneal injection of recombinant metrnl improves glucose tolerance in mice with high fat-induced obesity or type 2 diabetes (db/db), but this is not seen in AMPK {beta}1{beta}2 muscle-specific null mice (AMPK {beta}1{beta}2 MKO). In conclusion, we have demonstrated that metrnl induces beneficial effects on glucose metabolism via AMPK and is a promising therapeutic candidate for glucose-related diseases such as type 2 diabetes.

biochemistry↗