Biology subjects

Suner, I. G.

Publications and source records attributed to Suner, I. G..

4 recordsLinked to original sources

bioRxiv2023

A zebrafish knock-in reporter line for the Foxo1a transcription factor.

Zebrafish is a powerful model organism for in vivo live imaging. However, protein visualization relies to this date on the overexpression of fluorescently tagged proteins from a specific promoter which very often does not recapitulate endogenous patterns of expression and dynamics. Tagging proteins in the endogenous locus is not widely used in the field due to its technical inefficiency and difficulty. Here we developed a knock-in reporter line for the Foxo1a transcription factor by inserting an EGFP-pA cassette in frame at the C-terminal generating a fusion protein. Foxo1a has been involved in the regulation of many biological processes regarding metabolism, stress response, longevity, cell differentiation and others and its functions are conserved from invertebrates to vertebrates. Using in-vivo live imaging at early developmental stages, we validated the expression in the cardiovascular network, CNS, olfactory epithelium, spinal cord, retina, skeletal muscle, and myocardium. Our line opens the way for imaging studies aiming to characterize the expression and localization of this transcription factor in a tissue and context specific manner. Also, the knock-in line can be used in combination with other modern techniques to determine the transcriptional targets of Foxo1a, many of which remain unknown.

developmental biology↗

bioRxiv2023

Fluorescent Sensors for Imaging Interstitial Calcium

Calcium in interstitial fluids is central to systemic physiology and a crucial ion pool for entry into cells through numerous plasma membrane channels. Its study has been limited by the lack of methods that allow monitoring in tight inter-cell spaces at high spatio-temporal resolution. We engineered high performance ultra-low affinity genetically encoded calcium biosensors named GreenT-ECs. GreenT-ECs combine large fluorescence changes upon calcium binding and binding affinities (KD) ranging from 0.8 mM to 2.9 mM, making them uniquely tuned to calcium concentrations in extracellular organismal fluids. We validated GreenT-ECs in rodent hippocampal neurons and transgenic zebrafish in vivo, where the sensors enabled monitoring homeostatic regulation of tissue interstitial calcium. GreenT-ECs may become useful for recording very large calcium transients and for imaging calcium homeostasis in inter-cell structures in live tissues and organisms.

physiology↗

bioRxiv2022

Cellular senescence modulates progenitor cell expansion during axolotl limb regeneration

Axolotl limb regeneration is accompanied by the transient induction of cellular senescence within the blastema, the structure which nucleates regeneration. The precise role of this blastemal senescent cell (bSC) population, however, remains unknown. Here, through a combination of gain- and loss-of-function assays, we elucidate the functions and molecular features of cellular senescence in vivo. We demonstrate that cellular senescence plays a positive role during axolotl regeneration, by creating a pro-proliferative niche that supports progenitor cell expansion and blastema outgrowth. Senescent cells impact on their microenvironment via Wnt pathway modulation. Further, we uncover a link between Wnt signalling and senescence induction, and propose that bSC-derived Wnt signals facilitate the proliferation of neighbouring cells in part by preventing their induction into senescence. This work defines the roles of cellular senescence in regeneration of complex structures.

developmental biology↗

bioRxiv2022

Brown adipocytes local response to thyroid hormone is required for adaptive thermogenesis in adult male mice

Thyroid hormone (T3) and its nuclear receptors (TR) are important regulators of energy expenditure and adaptive thermogenesis, notably through their action in the brown adipose tissue (BAT). However, T3 acts in many other peripheral and central tissues which are also involved in energy expenditure. The general picture of how T3 regulates BAT thermogenesis is currently not fully established, notably due to the absence of extensive omics analyses and the lack of specific mice model. Here, we first used transcriptome and cistrome analyses to establish the list of T3/TR direct target genes in brown adipocytes. We then developed a novel model of transgenic mice, in which T3-signaling is specifically suppressed in brown adipocytes at adult stage. We addressed the capacity of these mice to mount a thermogenic response when challenged by either a cold exposure or a high-fat diet, and analyzed the associated changes in BAT transcriptome. We conclude that T3 plays a crucial role in the thermogenic response of the BAT, controlling the expression of genes involved in lipid and glucose metabolism and regulating BAT proliferation. The resulting picture provides an unprecedented view on the pathways by which T3 activates energy expenditure through an efficient adaptive thermogenesis in the BAT. Significance StatementThyroid hormones (TH) increase energy expenditure by regulating the expression of target genes in many metabolic tissues. Among them, brown adipose tissue (BAT) dissipates biochemical energy into heat production to notably prevent hypothermia during cold exposure. Hypothyroid mice display inefficient BAT thermogenesis suggesting that TH are crucial for this process. Here, we eliminated TH signaling specifically in brown adipocytes and expose the mice to different physiological stressors. We showed that TH signaling is crucial for BAT thermogenesis as it controls the expression of genes involved in proliferation and in the metabolism of lipids and glucose, the main energy resources for BAT thermogenesis. This study provides an unprecedented view on the pathways by which T3 activates energy expenditure the BAT.

genomics↗