Hematologic DNMT3A reduction and high-fat diet synergize to promote weight gain and tissue inflammation.

During aging, blood cell production becomes dominated by a limited number of variant hematopoietic stem cell (HSC) clones. Differentiated progeny of variant HSCs are thought to mediate the detrimental effects of such clonal hematopoiesis on organismal health, but the mechanisms are poorly understood. While somatic mutations in DNA methyltransferase 3A (DNMT3A) frequently drive clonal dominance, the aging milieu also likely contributes. Here, we examined in mice the interaction between high-fat diet (HFD) and reduced DNMT3A in hematopoietic cells; strikingly, this combination led to weight gain. HFD amplified pro-inflammatory pathways and upregulated inflammation-associated genes in mutant cells along a pro-myeloid trajectory. Aberrant DNA methylation during myeloid differentiation and in response to HFD led to pro-inflammatory activation and maintenance of stemness genes. These findings suggest that reduced DNMT3A in hematopoietic cells contributes to weight gain, inflammation, and metabolic dysfunction, highlighting a role for DNMT3A loss in the development of metabolic disorders.

Reactivation of the G1 enhancer landscape underlies core circuitry addiction to SWI/SNF.

Several cancer core regulatory circuitries (CRCs) depend on the sustained generation of DNA accessibility by SWI/SNF chromatin remodelers. However, the window when SWI/SNF is acutely essential in these settings has not been identified. Here we used neuroblastoma (NB) cells to model and dissect the relationship between cell-cycle progression and SWI/SNF ATPase activity. We find that SWI/SNF inactivation impairs coordinated occupancy of non-pioneer CRC members at enhancers within 1 hour, rapidly breaking their autoregulation. By precisely timing inhibitor treatment following synchronization, we show that SWI/SNF is dispensable for survival in S and G2/M, but becomes acutely essential only during G1 phase. We furthermore developed a new approach to analyze the oscillating patterns of genome-wide DNA accessibility across the cell cycle, which revealed that SWI/SNF-dependent CRC binding sites are enriched at enhancers with peak accessibility during G1 phase, where they activate genes involved in cell-cycle progression. SWI/SNF inhibition strongly impairs G1-S transition and potentiates the ability of retinoids used clinically to induce cell-cycle exit. Similar cell-cycle effects in diverse SWI/SNF-addicted settings highlight G1-S transition as a common cause of SWI/SNF dependency. Our results illustrate that deeper knowledge of the temporal patterns of enhancer-related dependencies may aid the rational targeting of addicted cancers.

Cancer cells driven by runaway transcription factor networks frequently depend on the cellular machinery that promotes DNA accessibility. For this reason, recently developed small molecules that impair SWI/SNF (or BAF) chromatin remodeling activity have been under active evaluation as anti-cancer agents. However, exactly when SWI/SNF activity is essential in dependent cancers has remained unknown. By combining live-cell imaging and genome-wide profiling in neuroblastoma cells, Cermakova et al. discover that SWI/SNF activity is needed for survival only during G1 phase of the cell cycle. The authors reveal that in several cancer settings, dependency on SWI/SNF arises from the need to reactivate factors involved in G1-S transition. Because of this role, authors find that SWI/SNF inhibition potentiates cell-cycle exit by retinoic acid.

Maternal metabolism influences neural tube closure.

Changes in maternal nutrient availability due to diet or disease significantly increase the risk of neural tube defects (NTDs). Because the incidence of metabolic disease continues to rise, it is urgent that we better understand how altered maternal nutrient levels can influence embryonic neural tube development. Furthermore, primary neurulation occurs before placental function during a period of histiotrophic nutrient exchange. In this review we detail how maternal metabolites are transported by the yolk sac to the developing embryo. We discuss recent advances in understanding how altered maternal levels of essential nutrients disrupt development of the neuroepithelium, and identify points of intersection between metabolic pathways that are crucial for NTD prevention.

The role of noncoding RNAs in pancreatic birth defects.

Congenital defects in the pancreas can cause severe health issues such as pancreatic cancer and diabetes which require lifelong treatment. Regenerating healthy pancreatic cells to replace malfunctioning cells has been considered a promising cure for pancreatic diseases including birth defects. However, such therapies are currently unavailable in the clinic. The developmental gene regulatory network underlying pancreatic development must be reactivated for in vivo regeneration and recapitulated in vitro for cell replacement therapy. Thus, understanding the mechanisms driving pancreatic development will pave the way for regenerative therapies. Pancreatic progenitor cells are the precursors of all pancreatic cells which use epigenetic changes to control gene expression during differentiation to generate all of the distinct pancreatic cell types. Epigenetic changes involving DNA methylation and histone modifications can be controlled by noncoding RNAs (ncRNAs). Indeed, increasing evidence suggests that ncRNAs are indispensable for proper organogenesis. Here, we summarize recent insight into the role of ncRNAs in the epigenetic regulation of pancreatic development. We further discuss how disruptions in ncRNA biogenesis and expression lead to developmental defects and diseases. This review summarizes in vivo data from animal models and in vitro studies using stem cell differentiation as a model for pancreatic development.

A pancreatic player in dementia: pathological role for islet amyloid polypeptide accumulation in the brain.

Type 2 diabetes mellitus patients have a markedly higher risk of developing dementia. While multiple factors contribute to this predisposition, one of these involves the increased secretion of amylin, or islet amyloid polypeptide, that accompanies the pathophysiology of type 2 diabetes mellitus. Islet amyloid polypeptide accumulation has undoubtedly been implicated in various forms of dementia, including Alzheimer's disease and vascular dementia, but the exact mechanisms underlying islet amyloid polypeptide's causative role in dementia are unclear. In this review, we have summarized the literature supporting the various mechanisms by which islet amyloid polypeptide accumulation may cause neuronal damage, ultimately leading to the clinical symptoms of dementia. We discuss the evidence for islet amyloid polypeptide deposition in the brain, islet amyloid polypeptide interaction with other amyloids implicated in neurodegeneration, neuroinflammation caused by islet amyloid polypeptide deposition, vascular damage induced by islet amyloid polypeptide accumulation, and islet amyloid polypeptide-induced cytotoxicity. There are very few therapies approved for the treatment of dementia, and of these, clinical responses have been controversial at best. Therefore, investigating new, targetable pathways is vital for identifying novel therapeutic strategies for treating dementia. As such, we conclude this review by discussing islet amyloid polypeptide accumulation as a potential therapeutic target not only in treating type 2 diabetes mellitus but as a future target in treating or even preventing dementia associated with type 2 diabetes mellitus.

KRAS Hijacks the miRNA Regulatory Pathway in Cancer.

Extensive studies have focused on the misregulation of individual miRNAs in cancer. More recently, mutations in the miRNA biogenesis and processing machinery have been implicated in several malignancies. Such mutations can lead to global miRNA misregulation, which may promote many of the well-known hallmarks of cancer. Interestingly, recent evidence also suggests that oncogenic Kristen rat sarcoma viral oncogene homolog (KRAS) mutations act in part by modulating the activity of members of the miRNA regulatory pathway. Here, we highlight the vital role mutations in the miRNA core machinery play in promoting malignant transformation. Furthermore, we discuss how mutant KRAS can simultaneously impact multiple steps of miRNA processing and function to promote tumorigenesis. Although the ability of KRAS to hijack the miRNA regulatory pathway adds a layer of complexity to its oncogenic nature, it also provides a potential therapeutic avenue that has yet to be exploited in the clinic. Moreover, concurrent targeting of mutant KRAS and members of the miRNA core machinery represents a potential strategy for treating cancer.

Human Islet Amyloid Polypeptide (hIAPP) Protofibril-Specific Antibodies for Detection and Treatment of Type 2 Diabetes.

Type 2 diabetes mellitus (T2D) is a major public health concern and is characterized by sustained hyperglycemia due to insulin resistance and destruction of insulin-producing ß cells. One pathological hallmark of T2D is the toxic accumulation of human islet amyloid polypeptide (hIAPP) aggregates. Monomeric hIAPP is a hormone normally co-secreted with insulin. However, increased levels of hIAPP in prediabetic and diabetic patients can lead to the formation of hIAPP protofibrils, which are toxic to ß cells. Current therapies fail to address hIAPP aggregation and current screening modalities do not detect it. Using a stabilizing capping protein, monoclonal antibodies (mAbs) can be developed against a previously nonisolatable form of hIAPP protofibrils, which are protofibril specific and do not engage monomeric hIAPP. Shown here are two candidate mAbs that can detect hIAPP protofibrils in serum and hIAPP deposits in pancreatic islets in a mouse model of rapidly progressing T2D. Treatment of diabetic mice with the mAbs delays disease progression and dramatically increases overall survival. These results demonstrate the potential for using novel hIAPP protofibril-specific mAbs as a diagnostic screening tool for early detection of T2D, as well as therapeutically to preserve ß cell function and target one of the underlying pathological mechanisms of T2D.

CHAF1A Blocks Neuronal Differentiation and Promotes Neuroblastoma Oncogenesis via Metabolic Reprogramming.

Neuroblastoma (NB) arises from oncogenic disruption of neural crest (NC) differentiation. Treatment with retinoic acid (RA) to induce differentiation has improved survival in some NB patients, but not all patients respond, and most NBs eventually develop resistance to RA. Loss of the chromatin modifier chromatin assembly factor 1 subunit p150 (CHAF1A) promotes NB cell differentiation; however, the mechanism by which CHAF1A drives NB oncogenesis has remained unexplored. This study shows that CHAF1A gain-of-function supports cell malignancy, blocks neuronal differentiation in three models (zebrafish NC, human NC, and human NB), and promotes NB oncogenesis. Mechanistically, CHAF1A upregulates polyamine metabolism, which blocks neuronal differentiation and promotes cell cycle progression. Targeting polyamine synthesis promotes NB differentiation and enhances the anti-tumor activity of RA. The authors' results provide insight into the mechanisms that drive NB oncogenesis and suggest a rapidly translatable therapeutic approach (DFMO plus RA) to enhance the clinical efficacy of differentiation therapy in NB patients.

Conformation-specific antibodies against multiple amyloid protofibril species from a single amyloid immunogen.

We engineered and employed a chaperone-like amyloid-binding protein Nucleobindin 1 (NUCB1) to stabilize human islet amyloid polypeptide (hIAPP) protofibrils for use as immunogen in mice. We obtained multiple monoclonal antibody (mAb) clones that were reactive against hIAPP protofibrils. A secondary screen was carried out to identify clones that cross-reacted with amyloid beta-peptide (Aß42) protofibrils, but not with Aß40 monomers. These mAbs were further characterized in several in vitro assays, in immunohistological studies of a mouse model of Alzheimer's disease (AD) and in AD patient brain tissue. We show that mAbs obtained by immunizing mice with the NUCB1-hIAPP complex cross-react with Aß42, specifically targeting protofibrils and inhibiting their further aggregation. In line with conformation-specific binding, the mAbs appear to react with an intracellular antigen in diseased tissue, but not with amyloid plaques. We hypothesize that the mAbs we describe here recognize a secondary or quaternary structural epitope that is common to multiple amyloid protofibrils. In summary, we report a method to create mAbs that are conformation-sensitive and sequence-independent and can target more than one type of protofibril species.

A prominent requirement for single-minded and the ventral midline in patterning the dorsoventral axis of the crustacean Parhyale hawaiensis.

In bilaterians, establishing the correct spatial positioning of structures along the dorsoventral (DV) axis is essential for proper embryonic development. Insects such as Drosophila rely on the Dorsal activity gradient and Bone morphogenetic protein (BMP) signaling to establish cell fates along the DV axis, leading to the distinction between tissues such as mesoderm, neurogenic ectoderm and dorsal ectoderm in the developing embryo. Subsequently, the ventral midline plays a more restricted role in DV patterning by establishing differential cell fates in adjacent regions of the neurogenic ectoderm. In this study, we examine the function of the ventral midline and the midline-associated gene single-minded (Ph-sim) in the amphipod crustacean Parhyale hawaiensis. Remarkably, we found that Ph-sim and the ventral midline play a central role in establishing proper fates along the entire DV axis in this animal; laser ablation of midline cells causes a failure to form neurogenic ectoderm and Ph-sim RNAi results in severely dorsalized embryos lacking both neurogenic ectoderm and the appendage-bearing lateral ectoderm. Furthermore, we hypothesize that this role of midline cells was present in the last common ancestor of crustaceans and insects. We predict that the transition to a Dorsal-dependent DV patterning system in the phylogenetically derived insect lineage leading to Drosophila has led to a more restricted role of the ventral midline in patterning the DV axis of these insects.