Biology subjects

Park, J.-C.

Publications and source records attributed to Park, J.-C..

9 recordsLinked to original sources

bioRxiv2026

Cryptic disease-prone states in human mesocortical assembloids revealed by multimodal profiling

Neurodegenerative diseases are characterized by synaptic failure, aberrant protein accumulation, and neuroglial dysfunction that emerge long before clinical onset. Although brain assembloids, which recapitulate interregional circuit connectivity beyond the scope of single organoids, significantly advance the modeling of circuit pathophysiology, they are predominantly evaluated through single-modality approaches that cannot resolve the functional and molecular heterogeneity underlying differential disease susceptibility. Here we show that morphologically identical human iPSC-derived dorso forebrain-midbrain mesocortical assembloids (MCAs) spontaneously bifurcate into disease-prone and non-prone states under identical culture conditions, revealing that MCA heterogeneity reflects intrinsic neurodegeneration susceptibility rather than stochastic culture variability. Using integrated electrophysiological, molecular, and spatial profiling, we find that disease-prone MCAs exhibit a temporally ordered molecular cascade in which neurofilament light chain elevation precedes tau dysregulation, mirroring the sequential biomarker trajectories observed in pre-symptomatic human neurodegeneration. Disease-prone MCAs further display selective cortical hyperexcitability and aberrant brainwave-like oscillatory dynamics that remain undetectable by any single modality. Spatially, a discrete junction-like neuronal population at the midbrain-forebrain interface shows transcriptional priming for synaptic overactivation alongside impaired astrocytic glutamate clearance, defining a spatially confined neuron-glial uncoupling as a candidate early origin of the disease-prone state. These findings reframe MCA heterogeneity as a biological window into pre-symptomatic neurodegeneration, with broad implications for disease modeling, risk stratification, and therapeutic discovery.

neuroscience↗

bioRxiv2024

AI-generated small binder improves prime editing

The prime editing 2 (PE2) system comprises a nickase Cas9 fused to a reverse transcriptase utilizing a prime editing guide RNA (pegRNA) to introduce desired mutations at target genomic sites. However, the PE efficiency is limited by mismatch repair (MMR) that excises the DNA strand containing desired edits. Thus, inhibiting key components of MMR complex through transient expression of a dominant negative MLH1 (MLH1dn) exhibited approximately 7.7-fold increase in PE efficiency over PE2, generating PE4. Herein, by utilizing a generative artificial intelligence (AI) technologies, RFdiffusion and AlphaFold 3, we ultimately generated a de novo MLH1 small binder (named MLH1-SB), which bind to the dimeric interface of MLH1 and PMS2 to disrupt the formation of key MMR components. MLH1-SBs small size (82 amino acids) allowed it to be integrated into pre-existing PE architectures via the 2A system, creating a novel PE-SB platform. Resultantly, by incorporating MLH1-SB into PE7, we have developed an improved PE architecture called PE7-SB, which demonstrates the highest PE efficiency to date (29.4-fold over PE2 and 2.4-fold over PE7 in HeLa cells), providing an insight that generative AI technologies will boost up the improvement of genome editing tools.

bioengineering↗

bioRxiv2024

Direct interrogation of context-dependent GPCR activity with a universal biosensor platform

G protein-coupled receptors (GPCRs) are the largest family of druggable proteins in the human genome, but progress in understanding and targeting them is hindered by the lack of tools to reliably measure their nuanced behavior in physiologically-relevant contexts. Here, we developed a collection of compact ONE vector G-protein Optical (ONE-GO) biosensor constructs as a scalable platform that can be conveniently deployed to measure G-protein activation by virtually any GPCR with high fidelity even when expressed endogenously in primary cells. By characterizing dozens of GPCRs across many cell types like primary cardiovascular cells or neurons, we revealed new insights into the molecular basis for G-protein coupling selectivity of GPCRs, pharmacogenomic profiles of anti-psychotics on naturally-occurring GPCR variants, and G-protein subtype signaling bias by endogenous GPCRs depending on cell type or upon inducing disease-like states. In summary, this open-source platform makes the direct interrogation of context-dependent GPCR activity broadly accessible.

biochemistry↗

bioRxiv2023

Fine-tuning GPCR-mediated neuromodulation by biasing signaling through different G-protein subunits

GPCRs mediate neuromodulation through activation of heterotrimeric G-proteins (G{beta}{gamma}). Classical models depict that G-protein activation leads to a one-to-one formation of G-GTP and G{beta}{gamma} species. Each of these species propagates signaling by independently acting on effectors, but the mechanisms by which response fidelity is ensured by coordinating G and G{beta}{gamma} responses remain unknown. Here, we reveal a paradigm of G-protein regulation whereby the neuronal protein GINIP biases inhibitory GPCR responses to favor G{beta}{gamma} over G signaling. Tight binding of GINIP to Gi-GTP precludes its association with effectors (adenylyl cyclase) and, simultaneously, with Regulator-of-G-protein-Signaling (RGS) proteins that accelerate deactivation. As a consequence, Gi-GTP signaling is dampened whereas G{beta}{gamma} signaling is enhanced. We show that this mechanism is essential to prevent imbalances of neurotransmission that underlie increased seizure susceptibility in vivo. Our findings reveal an additional layer of regulation within a quintessential mechanism of signal transduction that sets the tone of neurotransmission.

biochemistry↗

bioRxiv2023

Small-molecule targeting of GPCR-independent non-canonical G protein signaling inhibits cancer progression

Activation of heterotrimeric G-proteins (G{beta}{gamma}) by G-protein-coupled receptors (GPCRs) is a quintessential mechanism of cell signaling widely targeted by clinically-approved drugs. However, it has become evident that heterotrimeric G-proteins can also be activated via GPCR-independent mechanisms that remain untapped as pharmacological targets. GIV/Girdin has emerged as a prototypical non-GPCR activator of G proteins that promotes cancer metastasis. Here, we introduce IGGi-11, a first-in-class smallmolecule inhibitor of non-canonical activation of heterotrimeric G-protein signaling. IGGi-11 binding to G-protein -subunits (Gi) specifically disrupted their engagement with GIV/Girdin, thereby blocking non-canonical G-protein signaling in tumor cells, and inhibiting pro-invasive traits of metastatic cancer cells in vitro and in mice. In contrast, IGGi-11 did not interfere with canonical G-protein signaling mechanisms triggered by GPCRs. By revealing that small molecules can selectively disable non-canonical mechanisms of G-protein activation dysregulated in disease, these findings warrant the exploration of therapeutic modalities in G-protein signaling that go beyond targeting GPCRs.

biochemistry↗

bioRxiv2022

MSH2 and MSH6 as size dependent cellular determinants for prime editing in human embryonic stem cells

Potential applications of precise genome editing in human pluripotent stem cells (hPSCs), not only for isogenic disease modeling but also for ex vivo stem cell therapy, have urged the application of diverse genome editing tools in hPSCs. However, unlike differentiated somatic cells, the unique cellular properties of hPSCs (e.g., high susceptibility to DNA damage and active DNA repair) largely determine the overall efficiency of editing tools. Considering high demand of prime editors (PE), mostly due to its broad editing coverage compared to base editors, it is important to characterize the key molecular determinants of PE efficiency in hPSCs. Herein, we showed that MSH2 and MSH6, two main components of the MutS complex of mismatch repair (MMR), are highly expressed in hPSCs and determine PE efficiency in an editing size-dependent manner. Importantly, loss of MSH2, which disrupts both MutS and MutS{beta} complexes, was found to dramatically improve the efficiency of PE from one base to 10 bases, up to 50 folds. In contrast, genetic perturbation of MSH6, which solely abrogates MutS activity, marginally improved the editing efficiency up to 3 base pairs. The size dependent effect of MSH2 or MSH6 on prime editing in hPSCs not only implies MMR is a major determinant of PE efficiency in hPSCs but also highlights the distinct roles of MutS and MutS{beta} in the outcome of genome editing.

molecular biology↗

bioRxiv2021

NFIC regulates ribosomal biology and ER stress in pancreatic acinar cells and suppresses PDAC initiation

Tissue-specific differentiation is driven by specialized transcriptional networks. Pancreatic acinar cells crucially rely on the PTF1 complex, and on additional transcription factors, to deploy their transcriptional program. Here, we identify NFIC as a novel regulator of acinar differentiation using a variety of methodological strategies. NFIC binding sites are found at very short distances from NR5A2-bound genomic regions and both proteins co-occur in the same complex. Nfic knockout mice show reduced expression of acinar genes and, in ChIP-seq experiments, NFIC binds the promoters of acinar genes. In addition, NFIC binds to the promoter of, and regulates, genes involved in RNA and protein metabolism; in Nfic knockout mice, p-RS6K1 and p-IEF4E are down-regulated indicating reduced activity of the mTOR pathway. In 266-6 acinar cells, NFIC dampens the ER stress program through its binding to ER stress gene promoters and is required for complete resolution of Tunicamycin-mediated ER stress. Normal human pancreata from subjects with low NFIC mRNA levels display reduced epxression of genes down-regulated in Nfic knockout mice. Consistently, NFIC displays reduced expression upon induced acute pancreatitis and is required for proper recovery after damage. Finally, expression of NFIC is lower in samples of mouse and human pancreatic ductal adenocarcinoma and Nfic knockout mice develop an increased number of mutant Kras-driven pre-neoplastic lesions.

cell biology↗

bioRxiv2020

Efficient GNE myopathy disease modeling with mutation specific phenotypes in human pluripotent stem cells by base editors

Despite the great potential of disease modeling with the isogenic pairs of human pluripotent stem cells (hPSCs), the extremely low efficiency of precise gene editing in hPSCs remains a technical hurdle for this approach. Herein, we took advantage of currently available base editors (BEs) to epitomize the isogenic disease model from hPSCs. Using this method, we established 14 hPSCs that harbor point mutations on the GNE gene, including four different mutations found in GNE myopathy patients. Due to lesser activation of p53 by BEs than Cas9, a higher editing efficiency with BEs was achieved. Four different mutations in the epimerase or kinase domains of GNE revealed mutation-specific hyposialylation, which was closely correlated to pathological clinical phenotypes. These mutation-specific hyposialylation patterns were evident in GNE protein structure modeling. Furthermore, treatment with a drug candidate currently under clinical trials showed a mutation-specific drug response in GNE myopathy disease models. These data suggest that isogenic disease models from hPSCs using BEs could serve as a useful tool for mimicking the pathophysiology of GNE myopathy and for predicting drug responses.

developmental biology↗

bioRxiv2019

Scarless Enriched selection of Genome edited Human Pluripotent Stem Cells Using Induced Drug Resistance

An efficient gene editing technique for use in human pluripotent stem cells (hPSCs) would have great potential value in regenerative medicine, as well as in drug discovery based on isogenic human disease models. However, the extremely low efficiency of gene editing in hPSCs is a major technical hurdle that remains to be resolved. Previously, we demonstrated that YM155, a survivin inhibitor developed as an anti-cancer drug, induces highly selective cell death in undifferentiated hPSCs. In this study, we demonstrated that the high cytotoxicity of YM155 in hPSCs, which is mediated by selective cellular uptake of the drug, is due to high expression of SLC35F2 in these cells. Consistent with this, knockout of SLC35F2 with CRISPR-Cas9 or depletion with siRNAs made hPSCs highly resistant to YM155. Simultaneous gene editing of a gene of interest and transient knockdown of SLC35F2 following YM155 treatment enabled genome-edited hPSCs to survive because YM155 resistance was temporarily induced, thereby achieving enriched selection of genome-edited clonal populations. This precise and efficient genome editing approach took as little as 3 weeks without cell sorting or introduction of additional genes.

developmental biology↗