Biology subjects

Porter, G. A.

Publications and source records attributed to Porter, G. A..

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↗

bioRxiv2023

Mitochondrial citrate carrier SLC25A1 is a dosage-dependent regulator of metabolic reprogramming and morphogenesis in the developing heart

The developing mammalian heart undergoes an important metabolic shift from glycolysis toward mitochondrial oxidation, such that oxidative phosphorylation defects may present with cardiac abnormalities. Here, we describe a new mechanistic link between mitochondria and cardiac morphogenesis, uncovered by studying mice with systemic loss of the mitochondrial citrate carrier SLC25A1. Slc25a1 null embryos displayed impaired growth, cardiac malformations, and aberrant mitochondrial function. Importantly, Slc25a1 heterozygous embryos, which are overtly indistinguishable from wild type, exhibited an increased frequency of these defects, suggesting Slc25a1 haploinsuffiency and dose-dependent effects. Supporting clinical relevance, we found a near-significant association between ultrarare human pathogenic SLC25A1 variants and pediatric congenital heart disease. Mechanistically, SLC25A1 may link mitochondria to transcriptional regulation of metabolism through epigenetic control of gene expression to promote metabolic remodeling in the developing heart. Collectively, this work positions SLC25A1 as a novel mitochondrial regulator of ventricular morphogenesis and cardiac metabolic maturation and suggests a role in congenital heart disease.

developmental biology↗

bioRxiv2021

iPSC modeling shows uncompensated mitochondrial mediated oxidative stress underlies early heart failure in hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect with 30% mortality from heart failure (HF) in the first year of life, but why only some patients suffer early-HF and its cause remain unknown. Modeling using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) showed early-HF patient iPSC-CM have increased apoptosis, redox stress, and failed antioxidant response. This was associated with mitochondrial permeability transition pore (mPTP) opening, mitochondrial hyperfusion and respiration defects. Whereas iPSC-CM from patients without early-HF had hyper-elevated antioxidant response with increased mitochondrial fission and mitophagy. Single cell transcriptomics showed dichotomization by HF outcome, with mitochondrial dysfunction and endoplasmic reticulum (ER) stress associated with early-HF. Importantly, oxidative stress and apoptosis associated with early HF were rescued by sildenafil inhibition of mPTP opening or TUDCA suppression of ER stress. Together these findings demonstrate a new paradigm for modeling clinical outcome in iPSC-CM, demonstrating uncompensated mitochondrial oxidative stress underlies early HF in HLHS.

cell biology↗

bioRxiv2020

Neonatal hyperoxia inhibits proliferation of atrial cardiomyocytes by suppressing fatty acid synthesis

Preterm birth increases the risk for pulmonary hypertension and heart failure in adulthood. Oxygen therapy can damage the immature cardiopulmonary system and may be partially responsible for the cardiovascular disease in adults born preterm. We previously showed that exposing newborn mice to hyperoxia causes pulmonary hypertension by 1 year of age that is preceded by a poorly understood loss of pulmonary vein cardiomyocyte proliferation. We now show that hyperoxia also inhibits the proliferation of left atrial cardiomyocytes and causes diastolic heart failure by thinning the walls of the left atrium and disrupting its ability to pump effectively. Transcriptomic profiling showed that neonatal hyperoxia permanently suppressed fatty acid synthase (Fasn), stearoyl-CoA desaturase 1 (Scd1) and other fatty acid synthesis genes in the atria of mice, the HL-1 line of mouse atrial cardiomyocytes and left atrial tissue explanted from human infants. Suppressing Fasn or Scd1 reduced HL-1 cell proliferation while overexpressing these genes maintained their expansion in hyperoxic conditions, suggesting hyperoxia directly inhibits atrial cardiomyocyte proliferation by repressing Fasn and Scd1. Pharmacologic interventions that restore Fasn, Scd1 and other fatty acid synthesis genes in atrial cardiomyocytes may thus provide a way of ameliorating the adverse effects of supplemental oxygen on preterm infants.

developmental biology↗

bioRxiv2019

Early post-zygotic mutations contribute to congenital heart disease

BackgroundThe contribution of somatic mosaicism, or genetic mutations arising after oocyte fertilization, to congenital heart disease (CHD) is not well understood. Further, the relationship between mosaicism in blood and cardiovascular tissue has not been determined.\n\nResultsWe developed a computational method, Expectation-Maximization-based detection of Mosaicism (EM-mosaic), to analyze mosaicism in exome sequences of 2530 CHD proband-parent trios. EM-mosaic detected 326 mosaic mutations in blood and/or cardiac tissue DNA. Of the 309 detected in blood DNA, 85/97 (88%) tested were independently confirmed, while 7/17 (41%) candidates of 17 detected in cardiac tissue were confirmed. MosaicHunter detected an additional 64 mosaics, of which 23/46 (50%) among 58 candidates from blood and 4/6 (67%) of 6 candidates from cardiac tissue confirmed. Twenty-five mosaic variants altered CHD-risk genes, affecting 1% of our cohort. Of these 25, 22/22 candidates tested were confirmed. Variants predicted as damaging had higher variant allele fraction than benign variants, suggesting a role in CHD. The frequency of mosaic variants above 10% mosaicism was 0.13/person in blood and 0.14/person in cardiac tissue. Analysis of 66 individuals with matched cardiac tissue available revealed both tissue-specific and shared mosaicism, with shared mosaics generally having higher allele fraction.\n\nConclusionsWe estimate that ~1% of CHD probands have a mosaic variant detectable in blood that could contribute to cardiac malformations, particularly those damaging variants expressed at higher allele fraction compared to benign variants. Although blood is a readily-available DNA source, cardiac tissues analyzed contributed ~5% of somatic mosaic variants identified, indicating the value of tissue mosaicism analyses.

bioinformatics↗