Familial tooth agenesis (FTA) is one of the most common craniofacial anomalies in humans. Loss‐of‐function mutations in PAX9 and WNT10A have been known to cause FTA with various expressivity. In this ...study, we identified five FTA kindreds with novel PAX9 disease‐causing mutations: p.(Glu7Lys), p.(Val83Leu), p.(Pro118Ser), p.(Ser197Argfs*23), and c.771+4A>G. Concomitant PAX9 and WNT10A pathogenic variants found in two probands with severe phenotypes suggested an effect of mutational synergism. All overexpressed PAX9s showed proper nuclear localization, excepting the p.(Pro118Ser) mutant. Various missense mutations caused differential loss of PAX9 transcriptional ability. PAX9 overexpression in dental pulp cells upregulated LEF1 and AXIN2 expression, indicating a positive regulatory role for PAX9 in canonical Wnt signaling. Analyzing 176 cases with 63 different mutations, we observed a distinct pattern of tooth agenesis for PAX9‐associated FTA: Maxillary teeth are in general more frequently affected than mandibular ones. Along with all second molars, maxillary bicuspids and first molars are mostly involved, while maxillary lateral incisors and mandibular bicuspids are relatively less affected. Genotypically, missense mutations are associated with fewer missing teeth than frameshift and nonsense variants. This study significantly expands the phenotypic and genotypic spectrums of PAX9‐associated disorders and reveals a molecular mechanism of genetic synergism underlying FTA variable expressivity.
Familial tooth agenesis (FTA) is one of the most common craniofacial anomalies in humans. Loss‐of‐function mutations in PAX9 and WNT10A have been known to cause FTA with various expressivity. In this study, we identified 5 FTA kindreds with novel PAX9 disease‐causing mutations. Concomitant PAX9 and WNT10A pathogenic variants found in two probands with severe phenotypes suggested an effect of mutational synergism.
Activating transcription factor 5 (ATF5) is necessary for the development of various tissues, particularly under stress. Dysfunctions of ATF5 have been shown to be involved in many diseases. The ...exact function of ATF5 is tissue‐specific, and its role in erythropoiesis is still unknown. We here employed the loss of function strategy to investigate the role of ATF5 in murine erythropoiesis. We found that knockdown of Atf5 impaired the proliferation of fetal liver erythroid progenitors. Furthermore, erythroid differentiation was inhibited by ATF5 deficiency. Our study suggests that ATF5 may be a potential therapeutic target for treating blood diseases with ineffective erythropoiesis.
As essential components of hemoglobin, iron and heme play central roles in terminal erythropoiesis. The impairment of this process in iron/heme deficiency results in microcytic hypochromic anemia, ...the most prevalent anemia globally. Heme-regulated eIF2α kinase, also known as heme-regulated inhibitor (HRI), is a key heme-binding protein that senses intracellular heme concentrations to balance globin protein synthesis with the amount of heme available for hemoglobin production. HRI is activated during heme deficiency to phosphorylate eIF2α (eIF2αP), which simultaneously inhibits the translation of globin messenger RNAs (mRNAs) and selectively enhances the translation of activating transcription factor 4 (ATF4) mRNA to induce stress response genes. This coordinated translational regulation is a universal hallmark across the eIF2α kinase family under various stress conditions and is termed the integrated stress response (ISR). Inhibition of general protein synthesis by HRI-eIF2αP in erythroblasts is necessary to prevent proteotoxicity and maintain protein homeostasis in the cytoplasm and mitochondria. Additionally, the HRI–eIF2αP–ATF4 pathway represses mechanistic target of rapamycin complex 1 (mTORC1) signaling, specifically in the erythroid lineage as a feedback mechanism of erythropoietin-stimulated erythropoiesis during iron/heme deficiency. Furthermore, ATF4 target genes are most highly activated during iron deficiency to maintain mitochondrial function and redox homeostasis, as well as to enable erythroid differentiation. Thus, heme and translation regulate erythropoiesis through 2 key signaling pathways, ISR and mTORC1, which are coordinated by HRI to circumvent ineffective erythropoiesis (IE). HRI-ISR is also activated to reduce the severity of β-thalassemia intermedia in the Hbbth1/th1 murine model. Recently, HRI has been implicated in the regulation of human fetal hemoglobin production. Therefore, HRI-ISR has emerged as a potential therapeutic target for hemoglobinopathies.
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During erythroid differentiation and maturation, it is critical that the 3 components of hemoglobin, α-globin, β-globin, and heme, are made in proper stoichiometry to form stable hemoglobin. ...Heme-regulated translation mediated by the heme-regulated inhibitor kinase (HRI) provides one major mechanism that ensures balanced synthesis of globins and heme. HRI phosphorylates the α-subunit of eukaryotic translational initiation factor 2 (eIF2α) in heme deficiency, thereby inhibiting protein synthesis globally. In this manner, HRI serves as a feedback inhibitor of globin synthesis by sensing the intracellular concentration of heme through its heme-binding domains. HRI is essential not only for the translational regulation of globins, but also for the survival of erythroid precursors in iron deficiency. Recently, the protective function of HRI has also been demonstrated in murine models of erythropoietic protoporphyria and β-thalassemia. In these 3 anemias, HRI is essential in determining red blood cell size, number, and hemoglobin content per cell. Translational regulation by HRI is critical to reduce excess synthesis of globin proteins or heme under nonoptimal disease states, and thus reduces the severity of these diseases. The protective role of HRI may be more common among red cell disorders.
In this issue of
Blood
,
Huang et al
have identified activating transcription factor 4 (ATF4) as a novel regulator of fetal γ-globin gene expression in human cells by repressing BCL11A transcription.
...1
PURPOSE OF REVIEWThis review will provide an overview of the translational regulation of globin mRNAs and integrated stress response (ISR) during erythropoiesis by heme-regulated eIF2α kinase (HRI). ...HRI is an intracellular heme sensor that coordinates heme and globin synthesis in erythropoiesis by inhibiting protein synthesis of globins and heme biosynthetic enzymes during heme deficiency.
RECENT FINDINGSIt has been demonstrated recently that HRI also activates the eIF2αP–activating transcription factor 4 (ATF4) ISR in primary erythroid precursors to combat oxidative stress. During chronic iron/heme deficiency in vivo, this HRI–eIF2αP–ATF4 signaling is necessary both to reduce oxidative stress and to promote erythroid differentiation. Augmenting eIF2αP signaling by the small molecule salubrinal, which inhibits dephosphorylation of eIF2αP, reduces excess α-globin synthesis and enhances translation of ATF4 mRNA in mouse β-thalassemic erythroid precursors. Intriguingly, salubrinal treatment of differentiating human CD34 cells in culture increases fetal hemoglobin production with a concomitant decrease of adult hemoglobin by a posttranscriptional mechanism.
SUMMARYHRI–eIF2αP–ATF4 stress signaling is important not only to inhibit excess globin synthesis during erythropoiesis, but is also critical for adaptation to oxidative stress and for enhancing effective erythropoiesis. Modulation of this signaling pathway with small chemicals may provide a novel therapy for hemoglobinopathy.
T cells are strongly regulated by oxidizing environments and amino acid restriction. How T cells reprogram metabolism to adapt to these extracellular stress situations is not well understood. Here, ...we show that oxidizing environments and amino acid starvation induce ATF4 in CD4+ T cells. We also demonstrate that Atf4-deficient CD4+ T cells have defects in redox homeostasis, proliferation, differentiation, and cytokine production. We further reveal that ATF4 regulates a coordinated gene network that drives amino acid intake, mTORC1 activation, protein translation, and an anabolic program for de novo synthesis of amino acids and glutathione. ATF4 also promotes catabolic glycolysis and glutaminolysis and oxidative phosphorylation and thereby provides precursors and energy for anabolic pathways. ATF4-deficient mice mount reduced Th1 but elevated Th17 immune responses and develop more severe experimental allergic encephalomyelitis (EAE). Our study demonstrates that ATF4 is critical for CD4+ T cell-mediated immune responses through driving metabolic adaptation.
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•Oxidizing environments and amino acid starvation induce ATF4 in CD4+ T cells•ATF4 increases mTORC1 activation plus intake and de novo synthesis of amino acids•ATF4 enhances glycolysis, glutaminolysis, and oxidative phosphorylation•ATF4 deficiency leads to decreases in Th1 but increases in Th17 immune responses.
Oxidizing environments and availability of extracellular amino acids are major mechanisms that regulate T cell proliferation and function. Yang et al. demonstrate that ATF4 drives metabolic reprogramming, which allows CD4+ T cells to adapt to these stresses.
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Objectives: Miniscrews and miniplates are increasingly being used for absolute anchorage during orthodontic treatment. However, potential problems of damaging adjacent roots and their consequences ...during mini‐implant placement in the alveolar process have not been clearly described.
Materials and methods: Animal experiments were used to evaluate the stability of miniscrews placed with intentional root contact. The root repair was evaluated after screw removal. Seventy‐two miniscrews were surgically placed in the mandibular alveolar bone of six adult mongrel dogs with metabolic bone labeling at 3‐week intervals. Miniscrews of the experimental group were placed so that they contacted the root of the adjacent teeth, were retained for different time durations, and were then removed. The insertion torque, clinical measurements, removal torque, and histological findings were analyzed.
Results: (1) miniscrews contacting the roots showed a significantly higher insertion torque than those without contact; (2) there was a significant difference in the removal torque measurements based on the mobility of miniscrews and the state of root contact; and (3) miniscrews contacting the root were at greater risk of failure.
Conclusions: During placement of miniscrews in the aveolar process, increased failure rates were noticed among those contacting adjacent roots. Failed miniscrews appeared to be surrounded with a greater volume of soft tissue. When more inflammation was present, the adjacent roots seemed to experience more resorption. Nevertheless, the created lesion was repaired with a narrow zone of mineralized tissue deposited on the root surface, which was likely cellular cementum, and was mainly filled with alveolar bone, with the periodontal ligament space being maintained.
Pleural empyema is an inflammatory condition characterized by accumulation of pus inside the pleural cavity, which is usually followed by bacterial pneumonia. During the disease process, the ...pro-inflammatory and pro-fibrotic cytokines in the purulent pleural effusion cause proliferation of fibroblasts and deposition of extracellular matrix, which lead to fibrin deposition and fibrothorax. Urokinase instillation therapy through a chest drainage tube is frequently used for fibrinolysis in patients with empyema. However, urokinase treatment requires multiple instillation (2-3 times per day, for 4-8 days) and easily flows out from the chest drainage tube due to its high water solubility. In this in vitro study, we developed a thermo-responsive hydrogel based on poloxamer 407 (P407) combined with hyaluronic acid (HA) for optimal loading and release of urokinase. Our results show that the addition of HA to poloxamer gels provides a significantly more compact microstructure, with smaller pore sizes (**p < 0.001). The differential scanning calorimetry (DSC) profile revealed no influence on the micellization intensity of poloxamer gel by HA. The 25% poloxamer-based gel was significantly superior to the 23% poloxamer-based gel, with slower gel erosion when comparing the 16th hour residual gel weight of both gels (*p < 0.05; **p < 0.001). The 25% poloxamer-HA gel also exhibited a superior urokinase release profile and longer release time. A Fourier-transform infrared spectroscopy (FT-IR) study of the P407/HA hydrogel showed no chemical interactions between P407 and HA in the hydrogel system. The thermoresponsive P407/HA hydrogel may have a promising potential in the loading and delivery of hydrophilic drugs. On top of that, in vitro toxicity test of this combination demonstrates a lower toxicity.
In the current study, the mosquito larvicidal activity of leaf essential oils and their constituents from two eucalyptus species (
Eucalyptus camaldulensis and
Eucalyptus urophylla) against two ...mosquito species,
Aedes aegypti and
Aedes albopictus, was investigated. In addition, the chemical compositions of the leaf essential oils were analyzed using gas chromatography–mass spectrometry. Results from the larvicidal tests revealed that essential oil from the leaves of
E. camaldulensis had an excellent inhibitory effect against both
A. aegypti and
A. albopictus larvae. The 12 pure constituents extracted from the two eucalyptus leaf essential oils were also tested individually against two mosquito larvae. Among the six effective constituents, α-terpinene exhibits the best larvicidal effect against both
A. aegypti and
A. albopictus larvae. Results of this study show that the leaf essential oil of
E. camaldulensis and its effective constituents might be considered as a potent source for the production of fine natural larvicides.