Biology subjects

Laforest, B.

Publications and source records attributed to Laforest, B..

5 recordsLinked to original sources

bioRxiv2025

Generation and validation of an aryl hydrocarbon receptor knockout human embryonic stem cell line

Glucose homeostasis is tightly controlled by hormones secreted from pancreatic islets. The most abundant cell type in islets is the {beta}-cell, which secretes insulin in response to nutritional stimuli. We previously reported that the adverse metabolic effects of high-dose dioxin exposure in mice are regulated by the aryl hydrocarbon receptor (AHR) specifically in {beta}-cells. Additionally, fetal exposure to low-dose dioxin reduced {beta}-cell area in female mice at birth; however, the role of AHR in {beta}-cell development has not been explored. To characterize the AHR pathway in developing human {beta}-cells, we differentiated human embryonic stem cells (hESCs) into "islet-like" cell clusters (SC-islets) in vitro and treated cells with vehicle or dioxin for 24-hours at key stages of differentiation. Dioxin exposure robustly upregulated AHR gene targets (CYP1A1, AHRR) at all stages of differentiation but only had modest effects on markers of islet development and maturity. We next generated an AHR knock-out (KO) hESC line and found that basal CYP1A1 expression was profoundly suppressed in AHR-KO cells compared to parental cells at all stages of differentiation. Key markers of developing and mature pancreatic islets were largely unaffected by AHR deletion; however, G6PC2 was consistently downregulated in SC-islets from AHR-KO cells compared to parental cells. Interestingly, AHR-KO SC-islets also showed modestly increased insulin secretion relative to the parental line, suggesting a role for AHR in islet development. This novel AHR-KO cell line will allow for deeper investigation into the impact of AHR on development of human islets and other cell lineages.

developmental biology↗

bioRxiv2025

Nicotinic acetylcholine receptor signaling regulates cytokine production in Jurkat T cells

Nicotinic acetylcholine receptors (nAChRs) regulate immune cell functions, yet their expression patterns and roles in human T cells remain incompletely defined. The immunomodulatory effects of 7 nAChR signaling in human immune cells is complicated by the presence of the human-specific duplicated 7 (dup7) subunit. Here, we investigated the expression and function of nAChRs in human Jurkat T cells, focusing on 7, dup7, 9, and 10. Quantitative PCR revealed transcripts for all four subunits. Mitogenic stimulation with PMA, ionomycin, and ConA significantly downregulated 7, 9, and 10 expression while upregulating dup7, suggesting dynamic remodeling of receptor composition during T cell activation. Functional assays showed that 7 antagonism with ArIB[V11L,V16D] strongly suppressed mitogen-induced IL-2 and TNF- secretion, while nicotine pretreatment produced more modest reductions. Flow cytometry confirmed a decreased frequency of IL-2+ cells following treatment with nicotine or nAChR antagonists. These findings establish Jurkat cells as a tractable model for studying nAChR signaling in human T cells. Our results demonstrate that 7-containing nAChRs positively regulate cytokine production, while dup7 expression increases during activation and may act as a negative regulator of 7 function. Together, these data highlight nAChRs as key modulators of T cell activity and identify 7 and dup7 as potential therapeutic targets for regulating adaptive immunity.

immunology↗

bioRxiv2025

CD300LG is a receptor for triglyceride-rich lipoproteins that facilitates postprandial lipid clearance

Circulating triglycerides are principally transported by triglyceride-rich lipoprotein particles (TRLs) including very-low-density-lipoproteins (VLDL) and chylomicrons and require the activity of lipoprotein lipase for appropriate lipid processing and cellular uptake. Despite known genetic links between CD300LG variants and altered lipid profiles, the functional role of CD300LG in lipid metabolism remains unclear. In this study, we identify CD300LG as a crucial receptor for TRLs. Human genetic analyses reveal that reduced CD300LG protein levels are causally linked with CAD risk and increased number, diameter, and TAG concentration of TRLs. In mice, CD300LG deficiency results in postprandial hypertriglyceridemia independent of changes in VLDL secretion, intestinal lipid absorption, or lipoprotein lipase activity. Mechanistically, CD300LG acts as a receptor for TRLs through a direct interaction with ApoA4 to facilitate TRL clearance at the microvascular endothelium. These findings elucidate new functions for both CD300LG and ApoA4 and advance our general understanding of triglyceride metabolism.

physiology↗

bioRxiv2024

Coordinated Tbx3 / Tbx5 transcriptional control of the adult ventricular conduction system

The cardiac conduction system (CCS) orchestrates the electrical impulses that enable coordinated contraction of the cardiac chambers. The T-box transcription factors TBX3 and TBX5 are required for cardiac conduction system development and associated with overlapping and distinct human cardiac conduction system diseases. We evaluated the coordinated role of Tbx3 and Tbx5 in the murine ventricular conduction system (VCS). We engineered a compound Tbx3:Tbx5 conditional knockout allele for both genes located in cis on mouse chromosome 5. Conditional deletion of both T-box transcriptional factors in the ventricular conduction system, using the VCS-specific MinK:Cre, caused loss of VCS function and molecular identity. Combined Tbx3 and Tbx5 deficiency in the adult VCS led to conduction defects, including prolonged PR and QRS intervals and elevated susceptibility to ventricular tachycardia. These electrophysiological defects occurred prior to detectable alterations in cardiac contractility or histologic morphology, indicative of a primary conduction system defect. Tbx3:Tbx5 double knockout VCS cardiomyocytes revealed a transcriptional shift towards non-CCS-specialized working myocardium, indicating a change to their cellular identity. Furthermore, optical mapping revealed a loss of VCS-specific conduction system propagation. Collectively, these findings indicate that Tbx3 and Tbx5 coordinate to control VCS molecular fate and function, with implications for understanding cardiac conduction disorders in humans.

developmental biology↗

bioRxiv2020

Hox-dependent coordination of cardiac progenitor cell patterning and differentiation

Perturbation of addition of second heart field (SHF) cardiac progenitor cells to the poles of the heart tube results in congenital heart defects (CHD). The transcriptional programs and upstream regulatory events operating in different subpopulations of the SHF remain unclear. Here, we profile the transcriptome and chromatin accessibility of anterior and posterior SHF sub-populations at genome-wide levels and demonstrate that Hoxb1 negatively regulates differentiation in the posterior SHF. Spatial mis-expression of Hoxb1 in the anterior SHF results in hypoplastic right ventricle. Activation of Hoxb1 in embryonic stem cells arrests cardiac differentiation, whereas Hoxb1-deficient embryos display premature cardiac differentiation. Moreover, ectopic differentiation in the posterior SHF of embryos lacking both Hoxb1 and its paralog Hoxa1 results in atrioventricular septal defects. Our results show that Hoxb1 plays a key role in patterning cardiac progenitor cells that contribute to both cardiac poles and provide new insights into the pathogenesis of CHD.

developmental biology↗