Biology subjects

Mazine, A.

Publications and source records attributed to Mazine, A..

4 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↗

bioRxiv2025

Human pluripotent stem cell-derived atrioventricular node-like pacemaker cells exhibit biological conduction bridge properties in vitro and in vivo

The atrioventricular node (AVN) ensures synchronized heart contractions by establishing the electrical connection between the atria and ventricles. Dysfunction of the pacemaker cells of the AVN leads to atrioventricular block (AV block), a life-threatening condition managed with electronic pacemakers (EPMs). EPMs have drawbacks that could be overcome by a human pluripotent stem cell (hPSC)-derived biological conduction bridge (BioCB). Recent studies demonstrated the differentiation of AVN-like cells from hPSCs, but their conduction properties upon engraftment in vivo remain unexplored. Here we report the generation of AVN-like pacemaker cells (AVNLPCs) from hPSCs using WNT and BMP signaling modulation. These AVNLPCs transcriptionally resemble fetal AVN pacemaker cells, exhibit pacemaker action potentials, and display unique AVN-like conduction properties. Notably, when transplanted into the guinea pig heart, AVNLPCs replicate the functional properties of the AVN. Our study highlights the potential of an AVNLPC-based BioCB as novel cell therapy to improve treatment for AV block patients.

developmental biology↗

bioRxiv2024

Single-cell transcriptome analysis reveals CD34 as a novel marker of human sinoatrial node pacemaker cardiomyocytes

The sinoatrial node (SAN) regulates the heart rate throughout life. Failure of this primary pacemaker results in life-threatening, slow heart rhythm. Despite its important function, the cellular and molecular composition of the human SAN is not completely resolved. Particularly, no cell surface marker to identify and isolate SAN pacemaker cells has been reported to date. Here we used single-nuclei/cell RNA sequencing of fetal and human pluripotent stem cell (hPSC)- derived SAN cells and show that the SAN consists of three subtypes of pacemaker cells, including Core SAN, SAN, and Transitional Cells. Our study identified a host of novel Core SAN markers including MYH11, BMP4, and the cell surface antigen CD34. We demonstrate that sorting for CD34+ cells from cardiac hPSC differentiations enriches for SAN cells with a functional pacemaker phenotype. This novel SAN pacemaker cell surface marker is highly valuable for future hPSC- based disease modelling, drug discovery, cell replacement therapies, as well as the delivery of therapeutics to SAN cells in vivo using antibody-drug conjugates.

cell biology↗