Biology subjects

Colas, A. R.

Publications and source records attributed to Colas, A. R..

6 recordsLinked to original sources

bioRxiv2026

Tumor-derived SAA1-TLR4 signaling drives tumor-to-muscle communication in pancreatic cancer cachexia

Cancer cachexia limits treatment tolerance and survival in pancreatic ductal adenocarcinoma (PDAC), yet the tumor-derived signals driving tissue dysfunction remain poorly understood. Here, we identify serum amyloid A1 (SAA1) as a mediator of tumor-to-host communication acting through Toll-like receptor 4 (TLR4). Tumor-derived SAA1 was elevated in human PDAC and in a mouse PDAC model and disrupted both myofiber and muscle stem cell (MuSC) homeostasis. Genetic reduction of tumor-derived SAA1 uncoupled tumor progression from host wasting, preserving muscle mass and function and prolonging survival without affecting primary tumor growth. Mechanistically, SAA1-TLR4 signaling drove multicellular remodeling of the skeletal muscle microenvironment. Therapeutic TLR4 inhibition after cachexia onset restored muscle mass, function and MuSC abundance and prolonged survival independently of tumor growth. Conservation of SAA1-TLR4 signaling in human skeletal muscle identifies a therapeutically actionable tumor-host pathway and demonstrates that host deterioration can be targeted independently of tumor progression.

cancer biology↗

bioRxiv2023

The nutrient sensor CRTC & Sarcalumenin / Thinman represent a new pathway in cardiac hypertrophy

Obesity and type 2 diabetes are at epidemic levels and a significant proportion of these patients are diagnosed with left ventricular hypertrophy. CREB Regulated Transcription Co-activator (CRTC) is a key regulator of metabolism in mammalian hepatocytes, where it is activated by calcineurin (CaN) to increase expression of gluconeogenic genes. CaN is known its role in pathological cardiac hypertrophy, however, a role for CRTC in the heart has not been identified. In Drosophila, CRTC null mutants have little body fat and exhibit severe cardiac restriction, myofibrillar disorganization, cardiac fibrosis and tachycardia, all hallmarks of heart disease. Cardiac-specific knockdown of CRTC, or its coactivator CREBb, mimicked the reduced body fat and heart defects of CRTC null mutants. Comparative gene expression in CRTC loss- or gain-of-function fly hearts revealed contra-regulation of genes involved in glucose, fatty acid, and amino acid metabolism, suggesting that CRTC also acts as a metabolic switch in the heart. Among the contra-regulated genes with conserved CREB binding sites, we identified the fly ortholog of Sarcalumenin, which is a Ca2+-binding protein in the sarcoplasmic reticulum. Cardiac knockdown recapitulated the loss of CRTC cardiac restriction and fibrotic phenotypes, suggesting it is a downstream effector of CRTC we named thinman (tmn). Importantly, cardiac overexpression of either CaN or CRTC in flies caused hypertrophy that was reversed in a CRTC mutant background, suggesting CRTC mediates hypertrophy downstream of CaN, perhaps as an alternative to NFAT. CRTC novel role in the heart is likely conserved in vertebrates as knockdown in zebrafish also caused cardiac restriction, as in fl ies. These data suggest that CRTC is involved in myocardial cell maintenance and that CaN-CRTC- Sarcalumenin/tmn signaling represents a novel and conserved pathway underlying cardiac hypertrophy.

cell biology↗

bioRxiv2021

Conserved Transcription Factors Control Chromatin Accessibility and Gene Expression to Maintain Cell Fate Stability and Restrict Reprogramming of Differentiated Cells

The comprehensive characterization of mechanisms safeguarding cell fate identity in differentiated cells is crucial for 1) our understanding of how differentiation is maintained in healthy tissues or misregulated in disease states and 2) to improve our ability to use direct reprogramming for regenerative purposes. To uncover novel fate-stabilizing regulators, we employed a genome-wide TF siRNA screen followed by a high-complexity combinatorial evaluation of top performing hits, in a cardiac reprogramming assay in mouse embryonic fibroblasts, and subsequently validated our findings in cardiac, neuronal and iPSCs reprogramming assays in primary human fibroblasts and adult endothelial cells. This approach identified a conserved set of 4 TFs (ATF7IP, JUNB, SP7, and ZNF207 [AJSZ]) that robustly opposes cell fate reprogramming, as demonstrated by up to 6-fold increases in efficiency upon AJSZ knockdown in both lineage- and cell type-independent manners. Mechanistically, ChIP-seq and single-cell ATAC-seq analyses, revealed that AJSZ bind to both open and closed chromatin in a genome-wide and regionalized fashion, thereby limiting reprogramming TFs access to target DNA and ability to remodel the chromatin. In parallel, integration of ChIP-seq and RNA-seq data followed by systematic functional gene testing, identified that AJSZ also promote cell fate stability by proximally down-regulating a conserved set of genes involved in the regulation of cell fate specification (MEF2C), proteome remodeling (TPP1, PPIC), ATP homeostasis (EFHD1), and inflammation signaling (IL7R), thereby limiting cells ability to undergo large-scale phenotypic changes. Finally, simultaneous knock-down of AJSZ in combination with cardiac reprogramming TFs overexpression improved heart function by 250% as compared to no treatment and 50% as compared to MGT, 1 month after myocardial infarction. In sum, this study uncovers a novel evolutionarily conserved mechanism mediating cell fate stability in differentiated cells and also identifies AJSZ as promising therapeutic targets for regenerative purposes in adult organs. Significance StatementDifferentiated cells can be converted from one cell type into another by overexpressing lineage-determining transcription factors. Direct lineage reprogramming represents a promising strategy for regenerative medicine, but current clinical applications remain limited by the low yield of the reprogramming process. Here, we present the identification and detailed mechanistic study of a novel mechanisms opposing reprogramming process and promoting cell fate stability. Using a highthroughput screening technique, we identified four transcription factors that act as blockades to cell type change. By tracking chromatin and gene expression changes, we reconstructed a conserved pathway mediating cell fate stability in differentiated cells.

cell biology↗

bioRxiv2020

Lipid availability influences the metabolic maturation of human pluripotent stem cell-derived cardiomyocytes

ObjectivesPluripotent stem cell-derived cardiomyocytes are phenotypically immature, which limits their utility in downstream applications. Metabolism is dramatically reprogramed during cardiac maturation in vivo and presents a potential avenue to drive in vitro maturation. We aimed to identify and address metabolic bottlenecks in the generation of human pluripotent stem cell (hPSC)-derived cardiomyocytes. MethodshPSCs were differentiated into cardiomyocytes using an established, chemically-defined differentiation protocol. We applied 13C metabolic flux analysis (MFA) and targeted transcriptomics to characterize cardiomyocyte metabolism in during differentiation in the presence or absence of exogenous lipids. ResultshPSC-derived cardiomyocytes induced some cardiometabolic pathways (i.e. ketone body and branched-chain amino acid oxidation) but failed to effectively activate fatty acid oxidation. MFA studies indicated that lipid availability in cultures became limited during differentiation, suggesting potential issues with nutrient availability. Exogenous supplementation of lipids improved cardiomyocyte morphology, mitochondrial function, and promoted increased fatty acid oxidation in hPSC-derivatives. ConclusionhPSC-derived cardiomyocytes are dependent upon exogenous sources of lipids for metabolic maturation. Proper supplementation removes a potential roadblock in the generation of metabolically mature cardiomyocytes. These studies further highlight the importance of considering and exploiting metabolic phenotypes in the in vitro production and utilization of functional hPSC-derivatives.

cell biology↗

bioRxiv2020

PGC1/PPAR Drive Cardiomyocyte Maturation through Regulation of Yap1 and SF3B2

Cardiomyocytes undergo significant levels of structural and functional changes after birth--fundamental processes essential for the heart to produce the volume and contractility to pump blood to the growing body. However, due to the challenges in isolating single postnatal/adult myocytes, how individual newborn cardiomyocytes acquire multiple aspects of mature phenotypes remains poorly understood. Here we implemented large-particle sorting and analyzed single myocytes from neonatal to adult hearts. Early myocytes exhibited a wide-ranging transcriptomic and size heterogeneity, maintained until adulthood with a continuous transcriptomic shift. Gene regulatory network analysis followed by mosaic gene deletion revealed that peroxisome proliferator-activated receptor coactivator-1 signaling--activated in vivo but inactive in pluripotent stem cell-derived cardiomyocytes--mediates the shift. The signaling regulated key aspects of cardiomyocyte maturation simultaneously through previously unrecognized regulators, including Yap1 and SF3B2. Our study provides a single-cell roadmap of heterogeneous transitions coupled to cellular features and unveils a multifaceted regulator controlling cardiomyocyte maturation. Significance StatementHow the individual single myocytes achieve full maturity remains a black box, largely due to the challenges with the isolation of single mature myocytes. Understanding this process is particularly important as the immaturity and early developmental arrest of pluripotent stem cell-derived myocytes has emerged a major concern in the field. Here we present the first study of high-quality single-cell transcriptomic analysis of cardiac muscle cells from neonatal to adult hearts. We identify a central transcription factor and its novel targets that control key aspects of myocyte maturation, including cellular hypertrophy, contractility, and mitochondrial activity.

developmental biology↗

bioRxiv2019

Patient-specific functional genomics and disease modeling suggest a role for LRP2 in Hypoplastic Left Heart Syndrome

Congenital heart diseases (CHD), such as hypoplastic left heart syndrome (HLHS), are considered to have complex genetic underpinnings that are poorly understood. Here, an integrated multi-disciplinary approach was applied to identify novel genes and underlying mechanisms associated with HLHS. A family-based strategy was employed that coupled whole genome sequencing (WGS) with RNA sequencing of patient-derived induced pluripotent stem cells (iPSCs) from a sporadic HLHS proband-parent trio to identify, prioritize and functionally evaluate candidate genes in model systems. Consistent with the hypoplastic phenotype, the probands iPSCs had reduced proliferation capacity. Filtering WGS for rare de novo, recessive, and loss-of-function variants revealed 10 candidate genes with recessive variants and altered expression compared to the parents iPSCs. siRNA/RNAi-mediated knockdown in generic human iPSC-derived cardiac progenitors and in the in vivo Drosophila heart model revealed that LDL receptor related protein LRP2 and apolipoprotein APOB are required for robust hiPSC-derived cardiomyocyte proliferation and normal hear structure and function, possibly involving an oligogenic mechanism via growth-promoting WNT and SHH signaling. LRP2 was further validated as a CHD gene in a zebrafish heart model and rare variant burden testing in an HLHS cohort. Collectively, this cross-functional genetic approach to complex congenital heart disease revealed LRP2 dysfunction as a likely novel genetic driver of HLHS, and hereby established a scalable approach to decipher the oligogenic underpinnings of maladaptive left heart development. One sentence summaryWhole genome sequencing and a multi-model system candidate gene validation - human iPSC-derived cardiomyocytes and Drosophila and zebrafish hearts - identified lipoprotein LRP2 as a new potential driver in congenital heart disease and suggests a deficit in proliferation as a hallmark of hypoplastic left heart syndrome.

genetics↗