Biology subjects

Riemondy, K.

Publications and source records attributed to Riemondy, K..

3 recordsLinked to original sources

bioRxiv2026

Drosophila Arc1 is required for metabolic resilience and developmental timing during dietary challenges

Energy homeostasis at the organismal level requires balancing energy storage and mobilization to provide sufficient fuel for energy-intensive processes like development without depleting or accumulating excess stores. Fluctuations in the nutritional content of the diet present a challenge to the pathways that maintain energy balance. We previously identified the Drosophila melanogaster counterpart of human ARC (activity-regulated cytoskeleton-associated protein) as a brain-expressed protein that regulates energy storage in the major fat storage tissue of the fly, the fat body. Here we show that Arc1 expression in the brain responds to changes in diet and insulin-like peptide levels. Mutating Arc1 perturbs the ability of larvae to maintain normal body fat and rates of development upon dietary changes: mutants develop slower or faster than wild-type on nutrient-poor or nutrient-rich diets, respectively. Excess fat storage in Arc1 mutants becomes an advantage upon starvation, prolonging survival relative to the wild type. In addition to metabolic and neuronal genes, transcriptomic analysis revealed changes in key developmental drivers of development, in both diet-dependent and - independent manners. This study supports a model in which nutrient regulation of Arc1 via insulin-like peptide signaling couples dietary changes to changes in metabolism -- to maintain energy homeostasis -- and production of hormone signals, to support timely development. In this role, Arc1 is a central player in a buffering mechanism that coordinates nutrient availability, organismal metabolism, and developmental rate.

genetics↗

bioRxiv2021

RNA-binding proteins regulate aldosterone homeostasis in human steroidogenic cells

Angiotensin II (AngII) binds to the type I angiotensin receptor in the adrenal cortex to initiate a cascade of events leading to the production of aldosterone, a master regulator of blood pressure. Despite extensive characterization of the transcriptional and enzymatic control of adrenocortical steroidogenesis, there are still major gaps in our knowledge related to precise regulation of AII-induced gene expression kinetics. Specifically, we do not know the regulatory contribution of RNA-binding proteins (RBPs) and RNA decay, which can control the timing of stimulus-induced gene expression. To investigate this question, we performed a high-resolution RNA-seq time course of the AngII stimulation response and 4-thiouridine pulse labeling in a steroidogenic human cell line (H295R). We identified twelve temporally distinct gene expression responses that contained mRNA encoding proteins known to be important for various steps of aldosterone production, such as cAMP signaling components and steroidogenic enzymes. AngII response kinetics for many of these mRNAs revealed a coordinated increase in both synthesis and decay. These findings were validated in primary human adrenocortical cells stimulated ex vivo with AngII. Using a candidate siRNA screen, we identified a subset of RNA-binding protein and RNA decay factors that activate or repress AngII-stimulated aldosterone production. Among the repressors of aldosterone were BTG2, which promotes deadenylation and global RNA decay. BTG2 was induced in response to AngII stimulation and promoted the repression of mRNAs encoding pro-steroidogenic factors indicating the existence of an incoherent feedforward loop controlling aldosterone homeostasis. Together, these data support a model in which coordinated increases in transcription and regulated RNA decay facilitates the major transcriptomic changes required to implement a pro-steroidogenic gene expression program that is temporally restricted to prevent aldosterone overproduction.

genomics↗

bioRxiv2019

Simultaneous measurement of biochemical phenotypes and gene expression in single cells

Methods to measure heterogeneity among cells are rapidly transforming our understanding of biology but are currently limited to molecular abundance measurements. We developed an approach to simultaneously measure biochemical activities and mRNA abundance in single cells to understand the heterogeneity of DNA repair activities across thousands of human lymphocytes, identifying known and novel cell-type-specific DNA repair phenotypes. Our approach provides a general framework for understanding functional heterogeneity among single cells.

biochemistry↗