Biology subjects

Liu, C. Z.

Publications and source records attributed to Liu, C. Z..

5 recordsLinked to original sources

bioRxiv2026

Dysregulated TGFb-ERK Signaling Drives Aberrant Extracellular Matrix Production in Noonan Syndrome-Associated Pulmonary Valve Stenosis

Pulmonary valve stenosis (PVS) is the most common congenital heart defect in Noonan syndrome (NS) and related RASopathies, yet the molecular mechanisms linking pathogenic variants to the valve pathology remain poorly defined. Here, we utilized a human iPSC-based valve differentiation platform to generate the cardiac valve cell lineages--including fibrosa and spongiosa valve interstitial cell (VIC) subtypes. CRISPR-edited iPSCs harboring NS gain-of-function RAS/MAPK and Noonan syndrome with multiple lentigines (NSML) dominant-negative RAS/MAPK variants exhibited early defects in mesodermal and endocardial specification in all genotypes. Additionally, NS-iPSC endocardial cells exhibited defects in endothelial-to-mesenchymal transition (EndMT) specifically towards fibrosa VICs, which was most pronounced in PTPN11N308D (N308D) cells. Single-cell transcriptomics revealed widespread dysregulation of extracellular matrix (ECM) programs in N308D fibrosa VICs, including increased expression of collagens and proteoglycans, as well as dysregulation of multiple genes involved in ECM remodeling. We also detected activation of RAS-MAPK, TGF{beta}, and fibrosis-associated pathways in our transcriptional dataset. Mass spectrometry-based phosphoproteomics confirmed coordinated increases in ERK, PKC, and stress-related kinases, as well as enhanced activity of the TGF{beta} receptor. Functionally, N308D fibrosa VICs exhibited exaggerated upregulation of ECM genes in the presence of TGF{beta}2 ligand, suggesting that these cells are hypersensitive to TGF{beta} stimulation. Furthermore, we demonstrated that this pathological ECM-program occurs independently of BAMBI, a negative regulator of TGF{beta} signaling that was found to be decreased in N308D fibrosa VICs. Lastly, we performed histopathological analyses of stenotic pulmonary valves from two NS infants, which demonstrated marked overproduction and disorganization of ECM, mirroring the findings from our iPSC-based disease model. Together, our data reveal a central mechanism where NS-associated alleles sensitize fibrosa VICs to TGF{beta}, which leads to aberrant downstream signaling and drives the pathological ECM program in NS-associated PVS.

cell biology↗

bioRxiv2025

Generation of Valvular Interstitial Cells from Human Pluripotent Stem Cells

Heart valves are living structures whose sophisticated functions are mediated by a specialized population of mesenchymal cells known as valvular interstitial cells (VICs). Given their central role in valve homeostasis, VICs represent a promising cell population for studying heart valve diseases and developing novel therapies to treat them. Here, we describe a strategy for generating VICs from human pluripotent stem cells (hPSCs) by stage-specific manipulation of developmental signalling pathways. Our results demonstrate that hPSC-derived VICs show a high transcriptional similarity to primary human fetal VICs and can secrete key proteins of the valve extracellular matrix. We further investigate the heterogeneity of hPSC-derived VICs and identify two major subpopulations with distinct molecular and functional properties, mirroring the cellular diversity observed in vivo. Finally, we utilize an in vitro model of Noonan syndrome to demonstrate that hPSC-derived VICs can accurately recapitulate key aspects of valve disease. Collectively, these findings provide a reproducible method for the scaled generation of bona fide hPSC-derived VICs and establish their utility in disease modelling and tissue engineering applications. Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABS- We established a robust platform to generate bona fide valvular interstitial cells (VICs) from human pluripotent stem cells (hPSCs), recapitulating native VIC identity and function. - We delineated signaling pathways that promote the development of two distinct VIC subsets and identified a surface marker to distinguish between them. What are the clinical implications?- A renewable, human-specific source of VICs enables precise mechanistic studies of valve development and disease that are not possible with limited surgical specimens or animal models. - This platform creates opportunities for therapeutic applications, including drug discovery and tissue engineering approaches for valve repair.

cell biology↗

bioRxiv2023

Feeder-Free Generation of Endocardial and Cardiac Valve Cells from Human Pluripotent Stem Cells

Valvular heart disease presents a significant health burden, yet advancements in valve biology and novel therapeutics have been hindered by the lack of accessibility to human valve cells. In this study, we have developed a scalable and feeder-free method to differentiate human induced pluripotent stem cells (iPSCs) into endocardial cells. Importantly, we show that these endocardial cells are transcriptionally and phenotypically distinct from vascular endothelial cells and can be directed to undergo endothelial-to-mesenchymal transition (EndMT) to generate cardiac valve cell populations. Following this, we identified two distinct populations--one population undergoes EndMT to become valvular interstitial cells (VICs), while the other population reinforces their endothelial identity to become valvular endothelial cells (VECs). Lastly, we confirmed the identities of our iPSC-derived cell populations and identified putative markers through transcriptomic analyses. By increasing the accessibility to these cell populations, we aim to accelerate discoveries for cardiac valve biology and disease.

cell biology↗

bioRxiv2020

Interstitial spaces are continuous across tissue and organ boundaries in humans

Bodies have "reticular networks" comprising collagens, elastin, glycosaminoglycans, and other extracellular matrix components, that are continuous within and around all organs. Fibrous tissue coverings of nerves and blood vessels create structural continuity beyond organ boundaries. We recently described fluid flow through such human fibrous tissues. It remains unclear whether these interstitial spaces are continuous through the body or are discontinuous, confined within individual organs. We investigated IS continuity using two approaches. Non-biological particles (tattoo pigment, colloidal silver) were tracked within colon and skin interstitial spaces and into adjacent fascia. We also exploited hyaluronic acid, a macromolecular component of interstitial spaces. Both techniques demonstrate continuity of interstitial spaces within and across organ boundaries, including within perineurium and vascular adventitia traversing organs and the spaces between them. We suggest a body-wide network of fluid-filled interstitial spaces with significant implications for molecular signaling, cell trafficking, and the spread of malignant and infectious disease.

pathology↗

bioRxiv2020

Improved discrimination of asymmetric and symmetric arginine dimethylation by optimization of the normalized collision energy in LC-MS proteomics

Protein arginine methylation regulates diverse biological processes including signaling, metabolism, splicing, and transcription. Despite its important biological roles, arginine methylation remains an understudied post-translational modification. Partly, this is because the two forms of arginine dimethylation, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), are isobaric and therefore indistinguishable by traditional mass spectrometry techniques. Thus, there exists a need for methods that can differentiate these two modifications. Recently, it has been shown that the ADMA and SDMA can be distinguished by the characteristic neutral loss (NL) of dimethylamine and methylamine, respectively. However, the utility of this method is limited because the vast majority of dimethylarginine peptides do not generate measurable NL ions. Here, we report that increasing the normalized collision energy (NCE) in a higher-energy collisional dissociation (HCD) cell increases the generation of the characteristic NL that distinguish ADMA and SDMA. By analyzing both synthetic and endogenous methyl-peptides, we identify an optimal NCE value that maximizes NL generation and simultaneously improves methyl-peptide identification. Using two orthogonal methyl peptide enrichment strategies, high pH strong cation exchange (SCX) and immunoaffinity purification (IAP), we demonstrate that the optimal NCE increases improves NL-based ADMA and SDMA annotation and methyl peptide identifications by 125% and 17%, respectively, compared to the standard NCE. This simple parameter change will greatly facilitate the identification and annotation of ADMA and SDMA in mass spectrometry-based methyl-proteomics to improve our understanding of how these modifications differentially regulate protein function.

biochemistry↗