Histone Post-translational Modifications Research Articles

Histone H2A deubiquitinase BAP1 is essential for endothelial cell differentiation from human pluripotent stem cells.

Polycomb group proteins (PcGs) add repressive post translational histone modifications such as H2AK119ub1, and histone H2A deubiquitinases remove it. Mice lacking histone H2A deubiquitinases such as Usp16 and Bap1 die in embryonic stage, while mice lacking Usp3, Mysm1, Usp12, and Usp21 have been shown to be deficient in hematopoietic lineage differentiation, cell cycle regulation, and DNA repair. Thus, it is likely that histone deubiquitinases may also be required for human endothelial cell differentiation; however, there are no reports about the role of histone H2A deubiquitinase BAP1 in human endothelial cell development. We differentiated human pluripotent stem cells into the endothelial lineage which expressed stable inducible shRNA against BAP1. Our results show that BAP1 is required for human endothelial cell differentiation.

Mono-methylation of lysine 27 at histone 3 confers lifelong susceptibility to stress.

Histone post-translational modifications are critical for mediating persistent alterations in gene expression. By combining unbiased proteomics profiling and genome-wide approaches, we uncovered a role for mono-methylation of lysine 27 at histone H3 (H3K27me1) in the enduring effects of stress. Specifically, mice susceptible to early life stress (ELS) or chronic social defeat stress (CSDS) displayed increased H3K27me1 enrichment in the nucleus accumbens (NAc), a key brain-reward region. Stress-induced H3K27me1 accumulation occurred at genes that control neuronal excitability and was mediated by the VEFS domain of SUZ12, a core subunit of the polycomb repressive complex-2, which controls H3K27 methylation patterns. Viral VEFS expression changed the transcriptional profile of the NAc, led to social, emotional, and cognitive abnormalities, and altered excitability and synaptic transmission of NAc D1-medium spiny neurons. Together, we describe a novel function of H3K27me1 in the brain and demonstrate its role as a "chromatin scar" that mediates lifelong stress susceptibility.

Linking Aging to Cancer: The Role of Chromatin Biology.

Epigenetic changes have been established to be a hallmark of aging, which implies that aging science requires collaborating with the field of chromatin biology. DNA methylation patterns, changes in relative abundance of histone post-translational modifications, and chromatin remodeling are the central players in modifying chromatin structure. Aging is commonly associated with an overall increase in chromatin instability, loss of homeostasis, and decondensation. However, numerous publications have highlighted that the link between aging and chromatin changes is not nearly as linear as previously expected. This complex interplay of these epigenetic elements during the lifetime of an organism likely contributes to cellular senescence, genomic instability, and disease susceptibility. Yet, the causal links between these phenomena still need to be fully unraveled. In this perspective article, we discuss potential future directions of aging chromatin biology.

Single cell proteomics by mass spectrometry reveals deep epigenetic insight into the actions of an orphan histone deacetylase inhibitor.

Epigenetic programming has been shown to play a role in nearly every human system and disease where anyone has thought to look. However, the levels of heterogeneity at which epigenetic or epiproteomic modifications occur at single cell resolution across a population remains elusive. While recent advances in sequencing technology have allowed between 1 and 3 histone post-translational modifications to be analyzed in each single cell, over twenty separate chemical PTMs are known to exist, allowing thousands of possible combinations. Single cell proteomics by mass spectrometry (SCP) is an emerging technology in which hundreds or thousands of proteins can be directly quantified in typical human cells. As the proteins detected and quantified by SCP are heavily biased toward proteins of highest abundance, chromatin proteins are an attractive target for analysis. To this end, I applied SCP to the analysis of cancer cells treated with mocetinostat, a class specific histone deacetylase inhibitor. I find that 16 PTMs can be confidently identified and localized with high site specificity in single cells. In addition, the high abundance of histone proteins allows higher throughput methods to be utilized for SCP than ever described. While quantitative accuracy suffers when analyzing more than 700 cells per day, 9 histone proteins can be measured in single cells analyzed at even 3,500 cells per day, a throughput 10-fold greater than any previous report. In addition, the unbiased global approach utilized herein identifies a previously uncharacterized response to this drug through the S100-A8/S100-A9 protein complex partners. This response is observed in nearly every cell of the over 1,000 analyzed in this study, regardless of the relative throughput of the method utilized. While limitations exist in the methods described herein, current technologies can easily improve upon the results presented here to allow comprehensive analysis of histone PTMs to be performed in any mass spectrometry lab. All raw and processed data described in this study has been made publicly available through the ProteomeXchange/MASSIVE repository system as MSV000093434.

Improved Mass Spectrometry–Based Methods Reveal Abundant Propionylation and Tissue-Specific Histone Propionylation Profiles

Histone posttranslational modifications (PTMs) have crucial roles in a multitude of cellular processes, and their aberrant levels have been linked with numerous diseases, including cancer. Although histone PTM investigations have focused so far on methylations and acetylations, alternative long-chain acylations emerged as new dimension, as they are linked to cellular metabolic states and affect gene expression through mechanisms distinct from those regulated by acetylation. Mass spectrometry is the most powerful, comprehensive, and unbiased method to study histone PTMs. However, typical mass spectrometry–based protocols for histone PTM analysis do not allow the identification of naturally occurring propionylation and butyrylation. Here, we present improved state-of-the-art sample preparation and analysis protocols to quantitate these classes of modifications. After testing different derivatization methods coupled to protease digestion, we profiled common histone PTMs and histone acylations in seven mouse tissues and human normal and tumor breast clinical samples, obtaining a map of propionylations and butyrylations found in different tissue contexts. A quantitative histone PTM analysis also revealed a contribution of histone acylations in discriminating different tissues, also upon perturbation with antibiotics, and breast cancer samples from the normal counterpart. Our results show that profiling only classical modifications is limiting and highlight the importance of using sample preparation methods that allow the analysis of the widest possible spectrum of histone modifications, paving the way for deeper insights into their functional significance in cellular processes and disease states.

PARticular MARks: Histone ADP-ribosylation and the DNA Damage Response

Cellular and molecular responses to DNA damage are highly orchestrated and dynamic, acting to preserve the maintenance and integrity of the genome. Histone proteins bind DNA and organize the genome into chromatin. Post-translational modifications of histones have been shown to play an essential role in orchestrating the chromatin response to DNA damage by regulating the DNA damage response pathway. Among the histone modifications that contribute to this intricate network, histone ADP-ribosylation (ADPr) is emerging as a pivotal component of chromatin-based DNA damage response (DDR) pathways. In this review, we survey how histone ADPr is regulated to promote the DDR and how it impacts chromatin and other histone marks. Recent advancements have revealed histone ADPr effects on chromatin structure and the regulation of DNA repair factor recruitment to DNA lesions. Additionally, we highlight advancements in technology that have enabled the identification and functional validation of histone ADPr in cells and in response to DNA damage. Given the involvement of DNA damage and epigenetic regulation in human diseases including cancer, these findings have clinical implications for histone ADPr, which are also discussed. Overall, this review covers the involvement of histone ADPr in the DDR and highlights potential future investigations aimed at identifying mechanisms governed by histone ADPr that participate in the DDR, human diseases, and their treatments.

Epigenetics in Glaucoma.

Primary open angle glaucoma (POAG) is defined as a "genetically complex trait", where modifying factors act on a genetic predisposing background. For the majority of glaucomatous conditions, DNA variants are not sufficient to explain pathogenesis. Some genes are clearly underlying the more "Mendelian" forms, while a growing number of related polymorphisms in other genes have been identified in recent years. Environmental, dietary, or biological factors are known to influence the development of the condition, but interactions between these factors and the genetic background are poorly understood. Several studies conducted in recent years have led to evidence that epigenetics, that is, changes in the pattern of gene expression without any changes in the DNA sequence, appear to be the missing link. Different epigenetic mechanisms have been proven to lead to glaucomatous changes in the eye, principally DNA methylation, post-translational histone modification, and RNA-associated gene regulation by non-coding RNAs. The aim of this work is to define the principal epigenetic actors in glaucoma pathogenesis. The identification of such mechanisms could potentially lead to new perspectives on therapeutic strategies.

Heterochromatic 3D genome organization is directed by HP1a- and H3K9-dependent and independent mechanisms

Whether and how histone post-translational modifications and the proteins that bind them drive 3D genome organization remains unanswered. Here, we evaluate the contribution of H3K9-methylated constitutive heterochromatin to 3D genome organization in Drosophila tissues. We find that the predominant organizational feature of wild-type tissues is the segregation of euchromatic chromosome arms from heterochromatic pericentromeres. Reciprocal perturbation of HP1a⋅H3K9me binding, using a point mutation in the HP1a chromodomain or replacement of the replication-dependent histone H3 with H3K9R mutant histones, revealed that HP1a binding to methylated H3K9 in constitutive heterochromatin is required to limit contact frequency between pericentromeres and chromosome arms and regulate the distance between arm and pericentromeric regions. Surprisingly, the self-association of pericentromeric regions is largely preserved despite the loss of H3K9 methylation and HP1a occupancy. Thus, the HP1a⋅H3K9 interaction contributes to but does not solely drive the segregation of euchromatin and heterochromatin inside the nucleus.

Novel lactylation-related signature to predict prognosis for pancreatic adenocarcinoma.

Lactate, previously considered a metabolic byproduct, is pivotal in cancer progression and maintaining the immunosuppressive tumor microenvironment. Further investigations confirmed that lactate is a primary regulator, introducing recently described post-translational modifications of histone and non-histone proteins, termed lysine lactylation. Pancreatic adenocarcinomas are characterized by increased glycolysis and lactate accumulation. However, our understanding of lactylation-related genes in pancreatic adenocarcinomas remains limited. To construct a novel lactylation-related gene signature to predict the survival of patients with pancreatic cancer. RNA-seq and clinical data of pancreatic adenocarcinoma (PDAC) were obtained from the GTEx (Genotype-Tissue Expression) and TCGA (The Cancer Genome Atlas) databases via Xena Explorer, and GSE62452 datasets from GEO. Data on lactylation-related genes were obtained from publicly available sources. Differential expressed genes (DEGs) were acquired by using R package "DESeq2" in R. Univariate COX regression analysis, LASSO Cox and multivariate Cox regressions were produced to construct the lactylation-related prognostic model. Further analyses, including functional enrichment, ESTIMATE, and CIBERSORT, were performed to analyze immune status and treatment responses in patients with pancreatic cancer. PDAC and normal human cell lines were subjected to western blot analysis under lactic acid intervention; two PDAC cell lines with the most pronounced lactylation were selected. Subsequently, RT-PCR was employed to assess the expression of LRGs genes; SLC16A1, which showed the highest expression, was selected for further investigation. SLC16A1-mediated lactylation was analyzed by immunofluorescence, lactate production analysis, colony formation, transwell, and wound healing assays to investigate its role in promoting the proliferation and migration of PDAC cells. In vivo validation was performed using an established tumor model. In this study, we successfully identified 10 differentially expressed lactylation-related genes (LRGs) with prognostic value. Subsequently, a lactylation-related signature was developed based on five OS-related lactylation-related genes (SLC16A1, HLA-DRB1, KCNN4, KIF23, and HPDL) using Lasso Cox hazard regression analysis. Subsequently, we evaluated the clinical significance of the lactylation-related genes in pancreatic adenocarcinoma. A comprehensive examination of infiltrating immune cells and tumor mutation burden was conducted across different subgroups. Furthermore, we demonstrated that SLC16A1 modulates lactylation in pancreatic cancer cells through lactate transport. Both in vivo and in vitro experiments showed that decreasing SLC16A1 Level and its lactylation significantly inhibited tumor progression, indicating the potential of targeting the SLC16A1/Lactylation-associated signaling pathway as a therapeutic strategy against pancreatic adenocarcinoma. We constructed a novel lactylation-related prognostic signature to predict OS, immune status, and treatment response of patients with pancreatic adenocarcinoma, providing new strategic directions and antitumor immunotherapies.

Regulation of seed dormancy by histone post-translational modifications in the model plant Arabidopsis thaliana.

Plants synchronize their growth and development with environmental changes, which is critical for their survival. Among their life cycle transitions, seed germination is key for ensuring the survival and optimal growth of the next generation. However, even under favorable conditions, oftentimes germination can be blocked by seed dormancy, a regulatory multilayered checkpoint integrating internal and external signals. Intricate genetic and epigenetic mechanisms underlie seed dormancy establishment, maintenance, and release. In this review, we focus on recent advances that shed light on the complex mechanisms associated with physiological dormancy, prevalent in seed plants, with Arabidopsis thaliana serving as a model. Here, we summarize the role of multiple epigenetic regulators, but with a focus on histone modifications like acetylation and methylation, that finely tune dormancy responses and influence dormancy-associated gene expression. Understanding these mechanisms can lead to a better understanding of seed biology in general, as well as result in the identification of possible targets for breeding climate-resilient plants.

Histone lactylation regulates autophagy of hyperplastic scar fibroblasts by inhibiting the transcriptional activity of phosphatase and tensin homologue.

Hyperplastic scar (HS) is an overreaction of tissue to skin injury caused by local fibroblast proliferation and excessive collagen production. Histone posttranslational modification patterns are important epigenetic processes that control various biological activities. This study was designed to investigate the effects of histone lactylation on HS and the underlying mechanism. Western blot was used to analyse the lactylation level in HS patients and fibroblasts (HSFs). In vitro experiments, western blot, cell counting kit-8, and immunofluorescence staining were performed to detect the collagen level, cell viability, and autophagy, respectively. The relationship between snai2 (SLUG) and phosphatase and tensin homologue (PTEN) was assessed by RNA immunoprecipitation and dual-luciferase reporter assays. The results showed that the histone lactylation level was upregulated in HS tissues and HSFs. HSFs showed increased collagen production and cell viability, and decreased autophagy. Silencing of lactate dehydrogenase A (LDHA) promoted the transcription of PTEN by inhibiting SLUG, thus promoting autophagy. Knockdown of LDHA inhibited collagen deposition and cell viability, and increased autophagy in HSFs, and the results were reversed after PTEN inhibition. In summary, histone lactylation inhibited the transcription activity of PTEN by promoting SLUG, thereby suppressing autophagy and promoting collagen deposition and cell viability of HSFs, which might provide effective therapeutic strategies in HS.

Histone methylation: at the crossroad between circadian rhythms in transcription and metabolism.

Circadian rhythms, essential 24-hour cycles guiding biological functions, synchronize organisms with daily environmental changes. These rhythms, which are evolutionarily conserved, govern key processes like feeding, sleep, metabolism, body temperature, and endocrine secretion. The central clock, located in the suprachiasmatic nucleus (SCN), orchestrates a hierarchical network, synchronizing subsidiary peripheral clocks. At the cellular level, circadian expression involves transcription factors and epigenetic remodelers, with environmental signals contributing flexibility. Circadian disruption links to diverse diseases, emphasizing the urgency to comprehend the underlying mechanisms. This review explores the communication between the environment and chromatin, focusing on histone post-translational modifications. Special attention is given to the significance of histone methylation in circadian rhythms and metabolic control, highlighting its potential role as a crucial link between metabolism and circadian rhythms. Understanding these molecular intricacies holds promise for preventing and treating complex diseases associated with circadian disruption.

Histone H3 posttranslational modified enzymes defined neutrophil plasticity and their vulnerability to IL-10 in the course of the inflammation

BackgroundNeutrophils are a heterogeneous population capable of antimicrobial functions associated with pre-activation/activation and tissue regeneration. The specific polarisation of immune cells is mediated by the modification of ‘chromatin landscapes’, which enables differentiated access and activity of regulatory elements that guarantee their plasticity during inflammation No specific pattern within histone posttranslational modifications (PTMs) controlling this plasticity has been identified.MethodsUsing the in vitro model of inflammation, reflecting different states of neutrophils from resting, pre-activated cells to activated and reducing tissue regeneration, we have analysed 11 different histone posttranslational modifications (PTMs), PTM enzymes associated with remodelling neutrophil chromatin, and H3K4me3 ChIP-Seq Gene Ontology analysis focusing on the processes related to histone PTMs. These findings were verified by extrapolation to adequate clinical status, using neutrophils derived from the patients with sepsis (systemic septic inflammation with LPS-stimulated neutrophils), neuromyelitis optical spectrum disorders (aseptic inflammation with pre-activated neutrophils) and periodontitis (local self-limiting septic inflammation with IL-10-positive neutrophils).ResultsPhysiological activation of neutrophils comprises a pre-activation characterised by histone H3K27ac and H3K4me1, which position enhancers; direct LPS exposure is induced explicitly by H3K4me3 which marked Transcription Start Site (TSS) regions and low-level of H3K9me3, H3K79me2 and H3K27me3 which, in turn, marked repressed genes. Contrary to antimicrobial action, IL-10 positively induced levels of H3S10p and negatively H3K9me3, which characterised processes related to the activation of genes within heterochromatin mediated by CHD1 and H3K9me3 specific demethylase JMJD2A. IL-10 protects changes within histone PTMs induced by TNF or LPS that affected H3K4me3-specific methyltransferase SETD1A and MLL1. Neutrophils previously exposed to inflammatory factors become unvulnerable to IL-10 because previous LPS stimulation interrupts TSS regions marked by H3K4me3 of CHD1 and JMJD2A genes. Therefore, LPS-activated neutrophils are disabled to induce CHD1/JMJD2A enzymes by IL-10, making this process irreversible. Because transcription of JMJD2A and CHD1 also depends on TSS positioning by H3K4me3, neutrophils before LPS stimulation become insensitive to IL-10.ConclusionNeutrophils, once pre-activated by TNF or directly stimulated by LPS, become insensitive to the anti-inflammatory effects of IL-10, and vice versa; IL-10 protects neutrophils against these proinflammatory stimuli. This phenomenon is responsible for disturbing the natural process of resolving inflammation and tissue regeneration.Graphical

Impact of Combinatorial Histone Modifications on Acetyllysine Recognition by the ATAD2 and ATAD2B Bromodomains.

The ATPase family AAA+ domain containing 2 (ATAD2) protein and its paralog ATAD2B have a C-terminal bromodomain (BRD) that functions as a reader of acetylated lysine residues on histone proteins. Using a structure-function approach, we investigated the ability of the ATAD2/B BRDs to select acetylated lysine among multiple histone post-translational modifications. The ATAD2B BRD can bind acetylated histone ligands that also contain adjacent methylation or phosphorylation marks, while the presence of these modifications significantly weakened the acetyllysine binding activity of the ATAD2 BRD. Our structural studies provide mechanistic insights into how ATAD2/B BRD-binding pocket residues coordinate the acetyllysine group in the context of adjacent post-translational modifications. Furthermore, we investigated how sequence changes in amino acids of the histone ligands impact the recognition of an adjacent acetyllysine residue. Our study highlights how the interplay between multiple combinations of histone modifications influences the reader activity of the ATAD2/B BRDs, resulting in distinct binding modes.

Epigenetic and gene therapy in human and veterinary medicine.

Gene therapy is a focus of interest in both human and veterinary medicine, especially in recent years due to the potential applications of CRISPR/Cas9 technology. Another relatively new approach is that of epigenetic therapy, which involves an intervention based on epigenetic marks, including DNA methylation, histone post-translational modifications, and post-transcription modifications of distinct RNAs. The epigenome results from enzymatic reactions, which regulate gene expression without altering DNA sequences. In contrast to conventional CRISP/Cas9 techniques, the recently established methodology of epigenetic editing mediated by the CRISPR/dCas9 system is designed to target specific genes without causing DNA breaks. Both natural epigenetic processes and epigenetic editing regulate gene expression and thereby contribute to maintaining the balance between physiological functions and pathophysiological states. From this perspective, knowledge of specific epigenetic marks has immense potential in both human and veterinary medicine. For instance, the use of epigenetic drugs (chemical compounds with therapeutic potential affecting the epigenome) seems to be promising for the treatment of cancer, metabolic, and infectious diseases. Also, there is evidence that an epigenetic diet (nutrition-like factors affecting epigenome) should be considered as part of a healthy lifestyle and could contribute to the prevention of pathophysiological processes. In summary, epigenetic-based approaches in human and veterinary medicine have increasing significance in targeting aberrant gene expression associated with various diseases. In this case, CRISPR/dCas9, epigenetic targeting, and some epigenetic nutrition factors could contribute to reversing an abnormal epigenetic landscape to a healthy physiological state.

Lactylproteome analysis indicates histone H4K12 lactylation as a novel biomarker in triple-negative breast cancer.

The established link between posttranslational modifications of histone and non-histone lysine (K) residues in cell metabolism, and their role in cancer progression, is well-documented. However, the lactylation expression signature in triple-negative breast cancer (TNBC) remains underexplored. We conducted a comprehensive lactylproteome profiling of eight pairs of TNBC samples and their matched adjacent tissues. This was achieved through 4-Dimensional label-free quantitative proteomics combined with lactylation analysis (4D-LFQP-LA). The expression of identified lactylated proteins in TNBC was detected using immunoblotting and immunohistochemistry (IHC) with specific primary antibodies, and their clinicopathological and prognostic significance was evaluated. Our analysis identified 58 lactylation sites on 48 proteins, delineating the protein lactylation alteration signature in TNBC. Bioinformatic and functional analyses indicated that these lactylated proteins play crucial roles in regulating key biological processes in TNBC. Notably, lactylation of lysine at position 12 (H4K12lac) in the histone H4 domain was found to be upregulated in TNBC. Further investigations showed a high prevalence of H4K12lac upregulation in TNBC, with positive rates of 93.19% (137/147) and 92.93% (92/99) in TNBC tissue chip and validation cohorts, respectively. H4K12lac expression correlated positively with Ki-67 and inversely with overall survival (OS) in TNBC (HR [hazard ratio] =2.813, 95%CI [credibility interval]: 1.242-6.371, P=0.0164), suggesting its potential as an independent prognostic marker (HR=3.477, 95%CI: 1.324-9.130, P=0.011). Lactylation is a significant post-translational modification in TNBC proteins. H4K12lac emerges as a promising biomarker for TNBC, offering insights into the lactylation profiles of TNBC proteins and linking histone modifications to clinical implications in TNBC.

H2B oncohistones cause homologous recombination defect and genomic instability through reducing H2B monoubiquitination in Schizosaccharomyces pombe

Canonical oncohistones are histone H3 mutations in the N-terminal tail associated with tumors and affect gene expression by altering H3 post-translational modifications (PTMs) and the epigenetic landscape. Noncanonical oncohistone mutations occur in both tails and globular domains of all 4 core histones and alter gene expression by perturbing chromatin remodeling. However, the effects and mechanisms of noncanonical oncohistones remain largely unknown. Here we characterized 16 noncanonical H2B oncohistones in the fission yeast Schizosaccharomyces pombe. We found that 7 of them exhibited temperature sensitivities and 11 exhibited genotoxic sensitivities. A detailed study of 2 of these onco-mutants H2BG52D and H2BP102L revealed that they were defective in homologous recombination (HR) repair with compromised histone eviction and Rad51 recruitment. Interestingly, their genotoxic sensitivities and HR defects were rescued by inactivation of the H2BK119 deubiquitination function of Ubp8 in the Spt-Ada-Gcn5-Acetyltransferase (SAGA) complex. The levels of H2BK119 monoubiquitination (H2Bub) in the H2BG52D and H2BP102L mutants are reduced in global and local DNA break sites presumably due to enhanced recruitment of Ubp8 onto nucleosomes, and are recovered upon loss of H2B deubiquitination function of the SAGA complex. Moreover, H2BG52D and H2BP102L heterozygotes exhibit genotoxic sensitivities and reduced H2Bub in cis. We therefore conclude that H2BG52D and H2BP102L oncohistones affect HR repair and genome stability via reduction of H2Bub and propose that other noncanonical oncohistones may also affect histone PTMs to cause diseases.

Abstract PO5-24-05: The Metabolic and Epigenetic Contributions of Fibroblast Growth Factor Receptor-Mediated Breast Cancer Progression

Abstract Despite recent improvements in treatment options, breast cancer remains the second leading cause of cancer-related deaths among women, with metastasis of the primary tumor accounting for most of these deaths. Signaling by fibroblast growth factor receptors (FGFRs) is active in 85% of breast cancers and results in enhanced proliferation, migration, invasion, and therapeutic resistance of tumor cells. A common feature of breast cancer is altered cholesterol metabolism including an increase in cholesterol stored intracellularly as cholesteryl esters (CEs). In breast cancer cells, high levels of CEs are associated with aggressive disease and CEs are essential for growth and migration of cancer cells. Furthermore, there is mounting evidence that modifications to metabolic pathways impact epigenetic processes including DNA methylation and histone post-translational modifications. These epigenetic changes support tumor progression and metastasis through oncogene activation and silencing of tumor suppressors. While there have been numerous studies focused on the role of metabolic and epigenetic changes in breast cancer, none have attempted to connect these altered pathways to upstream growth factor receptor pathways, such as the FGFR pathway, in cancer cells. We hypothesize that FGFR signaling promotes changes to cholesterol metabolism and epigenetic regulation which lead to breast cancer progression. To study the proposed roles of FGFR signaling, we utilized murine mammary cells of differing metastatic abilities with inducible, oncogenic FGFR1 signaling. We also included the FGFR-dependent murine mammary tumor lines 4T1 and 4T07 which demonstrate differing metastatic capabilities. Through gene expression studies, we found an FGFR-mediated increase in cholesterol metabolic processes including cholesterol storage, uptake, and synthesis. Along with this, we found an FGFR-mediated increase in CE content in our models. Interestingly, these changes were exclusive to our highly metastatic models. Additionally, we have identified FGFR-mediated changes in the expression of histone modifying enzymes in our cell lines. Many of the enzymes modified by FGFR have been previously reported to play a role in breast cancer metastasis. To further elucidate the role of enhanced cholesterol storage in breast cancer progression, we treated cells with pharmacological inhibitors of cholesterol storage. Using in vitro assays, we demonstrate that cell survival, migration, and invasion all decrease when cholesterol storage is inhibited. Again, we observe that our highly metastatic cell line models are more sensitive to this inhibition. Taken together, these data suggest a role for FGFR signaling in promoting breast cancer progression and metastasis. With further studies, this connection may inform the development of novel therapeutic strategies to combat therapeutic resistance in breast cancer. Citation Format: Jennifer Tuokkola, Lyndsay Reese, Kaylee Schwertfeger. The Metabolic and Epigenetic Contributions of Fibroblast Growth Factor Receptor-Mediated Breast Cancer Progression [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-24-05.

The Impacts of Osmotic Stress During the Critical Window of Development on Protein and Histone PTM Alterations in California grunion

The California Grunion, Leuresthes tenuis, can experience a broad range of salinities during their early life stages, with their nursery grounds measuring salinities of 21 to 42ppt under normal conditions. Due to the unique subterrestrial incubation of their eggs within the sand of California beaches, it is not unlikely for this marine fish to hatch in non-seawater conditions, whereafter the larvae may transition to relatively diluted estuaries or concentrated harbors to develop as juveniles for several months. Consequently, they are an ideal system to study the impacts of ecologically relevant salinity stress on the alteration of proteins and histone post-translational modifications (PTMs) during early development. The study of the relationship between the critical window of development (CWD), in which sexual bipotential is lost, and the longevity of protein landscape and histone PTM changes has not been widely explored. The CWD is of interest as this is when the gametes of this species become set. Therefore, we hypothesize that histone PTM changes that occur during this time may thus be a form of heritable epigenetics. Thus, hypo-and-hyperosmotic exposures of L. tenuis hatchlings during this window, and past it, attempt to identify if the CWD is relevant to the presence and persistence of protein and histone PTM changes under salinity stress. We hypothesize that exposure to osmotic stress during the CWD will result in induced compensatory mechanisms in the protein landscape of the California grunion larvae, as well as persistent alterations in the histone PTMs in the larvae. To elucidate the relationship between these factors, California grunion larvae were exposed in replicate to one of three chronic salinity treatments (16ppt, 32ppt, or 40ppt) for the duration of their CWD (68dph), with 16ppt and 40ppt inducing hypoosmotic and hyperosmotic stress respectively. Chronic post-CWD exposures and recovery times until 98dph were used to determine whether the CWD or prolonged salinity exposures were key to alterations in the histone PTM and protein landscape of the larvae. After each timepoint, L. tenuis were culled and processed for histone PTM enrichment and proteomic analysis. At the time of culling, there were no significant differences in survivorship between replicates and experimental groups, with statistically significant different deaths between groups occurring only shortly after hatching. Skyline and MSstats were used in the analysis of the statistical significance of differential regulation of proteins and histone PTMs under stress conditions versus the controls. Of special interest is the osmoregulatory mechanisms involved in the myo-inositol biosynthesis pathway, with analysis focusing on the abundance of histone acetylation, amidation, ubiquitylation, and 4-hydroxynonelation in histone PTMs, as the accumulations of these have been found to be correlated with osmotic stress in some fish tissues. Funding provided by NSF IOS-2209383 and NSF GRFP. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

MSL2 variants lead to a neurodevelopmental syndrome with lack of coordination, epilepsy, specific dysmorphisms, and a distinct episignature

Epigenetic dysregulation has emerged as an important etiological mechanism of neurodevelopmental disorders (NDDs). Pathogenic variation in epigenetic regulators can impair deposition of histone post-translational modifications leading to aberrant spatiotemporal gene expression during neurodevelopment. The male-specific lethal (MSL) complex is a prominent multi-subunit epigenetic regulator of gene expression and is responsible for histone 4 lysine 16 acetylation (H4K16ac). Using exome sequencing, here we identify a cohort of 25 individuals with heterozygous de novo variants in MSL complex member MSL2. MSL2 variants were associated with NDD phenotypes including global developmental delay, intellectual disability, hypotonia, and motor issues such as coordination problems, feeding difficulties, and gait disturbance. Dysmorphisms and behavioral and/or psychiatric conditions, including autism spectrum disorder, and to a lesser extent, seizures, connective tissue disease signs, sleep disturbance, vision problems, and other organ anomalies, were observed in affected individuals. As a molecular biomarker, a sensitive and specific DNA methylation episignature has been established. Induced pluripotent stem cells (iPSCs) derived from three members of our cohort exhibited reduced MSL2 levels. Remarkably, while NDD-associated variants in two other members of the MSL complex (MOF and MSL3) result in reduced H4K16ac, global H4K16ac levels are unchanged in iPSCs with MSL2 variants. Regardless, MSL2 variants altered the expression of MSL2 targets in iPSCs and upon their differentiation to early germ layers. Our study defines an MSL2-related disorder as an NDD with distinguishable clinical features, a specific blood DNA episignature, and a distinct, MSL2-specific molecular etiology compared to other MSL complex-related disorders.