Kirthana Sarathy

Bio: Kirthana Sarathy is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Histone code & Histone methylation. The author has co-authored 1 publications.

Is There a Histone Code for Cellular Quiescence

Abstract: Many of the cells in our bodies are quiescent, that is, temporarily not dividing. Under certain physiological conditions such as during tissue repair and maintenance, quiescent cells receive the appropriate stimulus and are induced to enter the cell cycle. The ability of cells to successfully transition into and out of a quiescent state is crucial for many biological processes including wound healing, stem cell maintenance, and immunological responses. Across species and tissues, transcriptional, epigenetic, and chromosomal changes associated with the transition between proliferation and quiescence have been analyzed, and some consistent changes associated with quiescence have been identified. Histone modifications have been shown to play a role in chromatin packing and accessibility, nucleosome mobility, gene expression, and chromosome arrangement. In this review, we critically evaluate the role of different histone marks in these processes during quiescence entry and exit. We consider different model systems for quiescence, each of the most frequently monitored candidate histone marks, and the role of their writers, erasers and readers. We highlight data that support these marks contributing to the changes observed with quiescence. We specifically ask whether there is a quiescence histone "code," a mechanism whereby the language encoded by specific combinations of histone marks is read and relayed downstream to modulate cell state and function. We conclude by highlighting emerging technologies that can be applied to gain greater insight into the role of a histone code for quiescence.

Avatrombopag treatment response in patients with immune thrombocytopenia: the REAL-AVA 1.0 study

Abstract: Background: Thrombopoietin-receptor agonists (TPO-RAs) are used to treat immune thrombocytopenia (ITP), a disorder characterized by prolonged low platelet counts (PCs) that pose a risk of serious bleeding episodes. Avatrombopag (AVA) is the most recently approved TPO-RA for the treatment of chronic ITP. A high proportion of patients responded to AVA in clinical trials, and treatment was well-tolerated; however, limited real-world effectiveness data have been reported to date. Objectives: To describe demographic and clinical characteristics, treatment patterns, and outcomes following the initiation of AVA in patients with ITP in the United States. Design: This is a retrospective study using administrative claims data from the Komodo Healthcare Map (1 February 2017 to 28 February 2022) linked with PC laboratory data. Methods: Patients with ⩾1 diagnosis of ITP, ⩾1 paid prescription for AVA (index date), and ⩾1 month of pharmacy coverage after AVA initiation were selected. Baseline characteristics and follow-up steroid, immunosuppressant, and rescue medication use were described. The percentage of patients achieving clinically meaningful PC thresholds (⩾30 × 109/l) were assessed among patients with ⩾1 PC following AVA initiation and prior to AVA discontinuation/switch (effectiveness subgroup). Results: A total of 205 patients met eligibility criteria and 49% reported TPO-RA use in the prior 6 months. Approximately 70% and 93% of patients did not require use of steroid or immunoglobulin rescue medication during follow-up, respectively. Among patients with concomitant steroid (n = 75) or immunosuppressant (n = 7) use at AVA initiation, 35% and 57% discontinued those treatments, respectively. Of the 21 patients in the effectiveness subgroup, 81% achieved clinically meaningful PC thresholds. Conclusion: A high proportion of evaluable patients with ITP in this real-world study achieved clinically meaningful PCs, without requiring rescue medication during AVA treatment, with many able to discontinue baseline concomitant steroid or immunosuppressant utilization. Despite limited availability of PC data, these results are consistent with results from the AVA pivotal clinical trials.

Epigenetic aging in adult neurogenesis

Abstract: Neural stem cells (NSCs) in the hippocampus generate new neurons throughout life, which functionally contribute to cognitive flexibility and mood regulation. Yet adult hippocampal neurogenesis substantially declines with age and age-related impairments in NSC activity underlie this reduction. Particularly, increased NSC quiescence and consequently reduced NSC proliferation are considered to be major drivers of the low neurogenesis levels in the aged brain. Epigenetic regulators control the gene expression programs underlying NSC quiescence, proliferation and differentiation and are hence critical to the regulation of adult neurogenesis. Epigenetic alterations have also emerged as central hallmarks of aging, and recent studies suggest the deterioration of the NSC-specific epigenetic landscape as a driver of the age-dependent decline in adult neurogenesis. In this review, we summarize the recently accumulating evidence for a role of epigenetic dysregulation in NSC aging and propose perspectives for future research directions.

Lactate Rewrites the Metabolic Reprogramming of Uveal Melanoma Cells and Induces Quiescence Phenotype

Abstract: Uveal melanoma (UM), the most common primary intraocular cancer in adults, is among the tumors with poorer prognosis. Recently, the role of the oncometabolite lactate has become attractive due to its role as hydroxycarboxylic acid receptor 1 (HCAR1) activator, as an epigenetic modulator inducing lysine residues lactylation and, of course, as a glycolysis end-product, bridging the gap between glycolysis and oxidative phosphorylation. The aim of the present study was to dissect in UM cell line (92.1) the role of lactate as either a metabolite or a signaling molecule, using the known modulators of HCAR1 and of lactate transporters. Our results show that lactate (20 mM) resulted in a significant decrease in cell proliferation and migration, acting and switching cell metabolism toward oxidative phosphorylation. These results were coupled with increased euchromatin content and quiescence in UM cells. We further showed, in a clinical setting, that an increase in lactate transporters MCT4 and HCAR1 is associated with a spindle-shape histological type in UM. In conclusion, our results suggest that lactate metabolism may serve as a prognostic marker of UM progression and may be exploited as a potential therapeutic target.