Biology subjects

Yoon, J. S.

Publications and source records attributed to Yoon, J. S..

7 recordsLinked to original sources

bioRxiv2025

Hyper-proliferation of Adipose Progenitors During Developmental Adipogenesis Programs Higher Adipocyte Number and Early-onset Obesity in Offspring Born to Obese Dams

Being born to a mother who was obese during pregnancy is one of the strongest predictors of early onset obesity and metabolic syndrome. To identify the developmental mechanism linking maternal obesity to cardiometabolic disease in the offspring, a high fat/high fructose diet or low-fat control diet were introduced 4 weeks prior to mating in C57BL6 females and continued throughout pregnancy and lactation. Offspring born to obese dams had greater whole-body adiposity prior to puberty and were more susceptible to diet-induced obesity in adulthood. On postnatal day 10 (PND10) when pups born to obese dams had greater accumulation of subcutaneous adipose tissue, single cell sequencing was used to identify adipose progenitor cells (APCs) in the stromal vascular fraction. Two distinct lineages of APCs were identified that arose from a common proliferative root, terminating in committed preadipocytes and anti-adipogenic APCs. In pups born to obese dams, the proliferative root made up a greater proportion of APCs, more of these cells were in the G2M and S phases of the cell cycle and there was an enrichment in genes associated with proliferation (mKi67, Fat3, Ccn4, Gata4). On PND10, APCs isolated from the inguinal depots of pups born to obese dams were hyper-proliferative and there was a greater abundance of total APCs, whereas there were no differences in adipocyte size. After puberty, APCs in subcutaneous depots of offspring born to obese dams were more adipogenic in vitro and this group gained a greater amount of body fat in response to pharmacological stimulation of adipogenesis by rosiglitazone. Male adults born to obese dams had a lower abundance of APCs and were more susceptible to APC exhaustion due to prolonged exposure to rosiglitazone. Therefore, early onset obesity in offspring exposed to maternal obesity in utero is due to a prolongation of the proliferative phase of early life adipogenesis, leading to a higher adipocyte number.

developmental biology↗

bioRxiv2025

The strand-selective regulation of miR-155 response to lipopolysaccharide by CELF2, FUBP1 and KSRP proteins

The microRNA-155 exists in two forms, miR-155-5p and miR-155-3p, produced from either strand of the double-stranded precursor of miR-155. The more abundant and better-studied miR-155-5p has been implicated in many biological processes with dysregulated expression occurring in human diseases. miR-155-5p plays an essential role in supporting inflammatory responses in macrophages. Activating macrophages with lipopolysaccharide elevates miR-155-5p, while the anti-inflammatory cytokine interleukin-10 reduces miR-155-5p levels. Recently, miR-155-3p has also been suggested to participate in macrophage function, although its specific role is unclear. We found that LPS stimulation of macrophages results first in the elevation of miR-155-3p levels, followed by an increase in miR-155-5p levels. In this paper, we explore the mechanisms involved in the maturation of the pre-miR-155 to either miR-155-5p or miR-155-3p. We describe the contribution of three RNA-binding proteins, CELF2, FUBP1 and KSRP, to pre-miR-155 processing. Our data suggests CELF2 regulates miR-155-5p/miR-155-3p strand selection. FUBP1 may support the expression of miR-155-3p for specific subcellular functions, while KSRP appears to inhibit both miR-155-5p and miR-155-3p maturation without altering the relative expression of each strand.

immunology↗

bioRxiv2024

Upregulation of a nonsense mediated decay (NMD) insensitive CFTR mRNA isoform has therapeutic potential for the treatment of 3 Prime CFTR PTC variants

BackgroundNonsense or Premature Termination Codon (PTC) mutations of the CFTR gene are pathogenic and found in [~]10% of North American people with cystic fibrosis. PTC mutations induce Nonsense-Mediated mRNA Decay (NMD), leading to a substantial ([~]80-90%) reduction in full-length mRNA. This reduction is a key contributor to PTC mutation-related pathology. Various approaches to evade NMD and preserve the impacted mRNA transcript have been explored but have not progressed to clinical development, leaving NMD a significant hurdle for PTC readthrough therapy. MethodsAntisense oligonucleotides (ASOs) were tiled across intron 22 splice donor (SD) and acceptor (SA) sites of the CFTR gene. Immortalized airway cells were treated with SD and SA ASOs, and those yielding the greatest increase in a CFTR NMD-insensitive mRNA isoform (e22 trunc mRNA) were tested in combinations. Top SD/SA ASO pairs were assessed for their impact on e22 trunc mRNA via ddPCR, e22 trunc protein via western blot, and CFTR-mediated chloride (Cl-) transport via transepithelial electrophysiological measurements in immortalized and primary human bronchial epithelial (hBE) cell cultures. ResultsWe demonstrate that e22 trunc mRNA generates a truncated CFTR protein whose Cl- transport function can be enhanced with elexacaftor/tezacaftor/ivacaftor (ETI) treatment. ASO and ETI treatment in combination restore [~]20% and 25% of wild-type CFTR Cl- transport function in immortalized epithelial and primary hBE cells homozygous for CFTR W1282X, respectively. ConclusionsThis study lays the groundwork for advancing ASO-mediated upregulation of e22 trunc mRNA and protein as a therapeutic approach for cystic fibrosis caused by 3-terminal CFTR PTC mutations.

genomics↗

bioRxiv2024

NPAS4 is an allostatic regulator of POMC neuronal activity during diet-induced obesity

RationaleObesity is characterized by a chronic positive energy balance and altered function of cell types that regulate food intake. These cell types include proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) of the hypothalamus that detect peripheral signals and promote a reduction in food intake upon activation. Downstream of neuronal activation, activity- regulated genes such as Neuronal PAS domain protein 4 (Npas4) are induced as part of the response to environmental stimuli. Npas4 is known to have cytoprotective roles in both neurons and pancreatic beta cells. A previous Npas4 knockout study in both mouse pancreatic beta cells and ARC neurons implied a potential role of Npas4 in regulating food intake. However, the specific sites of Npas4 action in the ARC are unknown. We hypothesized that Npas4 in POMC neurons of the ARC has a role in regulating food intake during obesity. MethodsWe quantified Npas4 expression in POMC neurons of the arcuate nucleus in mice exposed to various positive energy states known to activate POMC neurons using RNAscope fluorescent in situ hybridization. Next, we generated adult male mice with a conditional Npas4 knockout specifically in their ARC POMC neurons (POMC-NPAS4 KO) and metabolically characterized them for 30 weeks on regular chow or 60% high-fat diet (HFD) at room temperature. In addition, we performed single cell RNA sequencing (scRNA-seq) on microdissected ARC tissue and neighbouring regions from fasted or 1hr refed POMC-NPAS4 KO mice and controls at 6 weeks of HFD, in order to identify Npas4-regulated and feeding- regulated transcriptional changes in POMC neurons. ResultsNpas4 was expressed in POMC neurons, and its expression was induced in response to positive energy states such as refeeding, oral glucose, and acute HFD feeding. HFD-fed POMC- NPAS4 KO males showed significantly reduced body weight starting at 10 weeks of HFD, and weighed 8-10 grams less than controls by 30 weeks. With metabolic cages and manual food intake measurements, we determined this difference was not the result of increased energy expenditure or physical activity, but was due to decreased food intake prior to the observed lack of gain in body weight. Using the ARC single-cell dataset, we found that POMC neurons of KO mice showed an enhanced refeeding-induced transcriptional response, dysregulated immediate early gene expression in response to refeeding, and reduced expression of genes encoding GABA-A receptor subunits. Furthermore, cell-to-cell communication analysis revealed that POMC neurons of KO mice specifically lost inhibitory GABAergic signaling inputs, some of which came from agouti-related protein (AgRP) neurons, and gained excitatory glutamatergic signaling inputs compared to POMC neurons of control littermates. ConclusionsTaken together, the results suggest that activity-dependent expression of Npas4 in POMC neurons tempers the activity of these cells upon overnutrition. Loss of Npas4 causes cell- autonomous loss of the capacity to sense nutrient intake. Molecularly, this is driven by reduced expression of inhibitory GABA-A receptors and an overall increase in POMC neuronal activity, leading to decreased food intake and decreased weight gain. In conclusion, for the first time we report a role for the transcription factor Npas4 in POMC neurons of the ARC, and demonstrate it plays an indispensable role in controlling feeding behavior in states of overnutrition.

physiology↗

bioRxiv2023

Calcium-dependent transcriptional profiles of human pancreatic islet cells reveal functional diversity in islet subpopulations

Aims/hypothesisPancreatic islets depend on cytosolic calcium to trigger the secretion of glucoregulatory hormones and regulate the transcription of genes important for the response to stimuli. To date, there has not been an attempt to profile calcium-regulated gene expression in all islet cell types. Our aim was to construct a large single-cell transcriptomic dataset from human islets exposed to conditions that would acutely induce or inhibit intracellular calcium signalling, while preserving biological heterogeneity. MethodsWe exposed intact human islets from three donors to the following conditions: (1) 2.8 mM glucose; (2) 25 mM glucose and 40 mM KCl to maximally stimulate calcium signalling; and (3) 25 mM glucose, 40 mM KCl and 5 mM EGTA (calcium chelator) to inhibit calcium signalling, for 1 hour. We sequenced 43,909 cells from all islet cell types, and further subsetted the cells to form an endocrine cell-specific dataset of 32,486 cells expressing INS, GCG, SST or PPY. We compared transcriptomes across conditions to determine the differentially expressed calcium-regulated genes in each endocrine cell type, and in each endocrine cell subcluster of alpha and beta cells. ResultsBased on the number of calcium-regulated genes, we found that each alpha and beta cell cluster had a different magnitude of calcium response. We also showed that a polyhormonal cluster expressing INS, GCG, and SST is defined by calcium-regulated genes specific to this cluster. Finally, we identified the gene PCDH7 from the beta cell clusters that had the highest number of calcium-regulated genes, and showed that cells expressing cell surface PCDH7 protein have enhanced glucose-stimulated insulin secretory function. ConclusionsHere we use our single-cell dataset to show that human islets have cell-type-specific calcium-regulated gene expression profiles, some of them specific to subpopulations. In our dataset, we identify PCDH7 as a novel marker of beta cells having an increased number of calcium-regulated genes and enhanced insulin secretory function. Data availabilityA searchable and user-friendly format of the data in this study, specifically designed for rapid mining of single-cell RNA sequencing data, is available at https://lynnlab.shinyapps.io/Hislet_2023/. The raw data files are available at NCBI Gene Expression Omnibus (GSE196715).

physiology↗

bioRxiv2022

Efficacy and Specificity of Melanopsin Reporters for Retinal Ganglion Cells

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are specialized retinal output neurons that mediate behavioral, neuroendocrine, and developmental responses to environmental light. There are diverse molecular strategies for marking ipRGCs, especially in mice, making them among the best characterized retinal ganglion cells. With the development of more sensitive reporters, new subtypes of ipRGCs have emerged. We therefore tested high-sensitivity reporter systems to see whether we could reveal yet more. Substantial confusion remains about which of the available methods, if any, label all and only ipRGCs. Here, we compared many different methods for labeling of ipRGCs, including anti-melanopsin immunofluorescence, Opn4-GFP BAC transgenic mice, and Opn4cre mice crossed with three different Cre-specific reporters (Z/EG; Ai9; and Ai14) or injected with Cre-dependent (DIO) AAV2. We show that Opn4cre mice, when crossed with sensitive Cre-reporter mice, label numerous ganglion cell types that lack intrinsic photosensitivity. Though other methods label ipRGCs specifically, they do not label the entire population of ipRGCs. We conclude that no existing method labels all and only ipRGCs. We assess the appropriateness of each reporter for particular applications and integrate findings across reporters to estimate that the overall abundance of ipRGCs among mouse retinal ganglion cells may approach 11%.

neuroscience↗

bioRxiv2018

Engineered transfer RNAs for suppression of premature termination codons

Premature termination codons (PTCs) are responsible for 10-15% of all inherited disease. PTC suppression during translation offers a promising approach to treat a variety of genetic disorders, yet small molecules that promote PTC read-through have yielded mixed performance in clinical trials. We present a high-throughput, cell-based assay to identify anticodon engineered transfer RNAs (ACE-tRNA) which can effectively suppress in-frame PTCs and faithfully encode their cognate amino acid. In total, we identified ACE-tRNA with a high degree of suppression activity targeting the most common human disease-causing nonsense codons. Genome-wide transcriptome ribosome profiling of cells expressing ACE-tRNA at levels which repair PTC indicate that there are limited interactions with translation termination codons. These ACE-tRNAs display high suppression potency in mammalian cells, Xenopus oocytes and mice in vivo, producing PTC repair in multiple genes, including disease causing mutations within the cystic fibrosis transmembrane conductance regulator (CFTR).

molecular biology↗