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1.
Nat Commun ; 15(1): 5937, 2024 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-39009564

RESUMO

How disruptions to normal cell differentiation link to tumorigenesis remains incompletely understood. Wilms tumor, an embryonal tumor associated with disrupted organogenesis, often harbors mutations in epigenetic regulators, but their role in kidney development remains unexplored. Here, we show at single-cell resolution that a Wilms tumor-associated mutation in the histone acetylation reader ENL disrupts kidney differentiation in mice by rewiring the gene regulatory landscape. Mutant ENL promotes nephron progenitor commitment while restricting their differentiation by dysregulating transcription factors such as Hox clusters. It also induces abnormal progenitors that lose kidney-associated chromatin identity. Furthermore, mutant ENL alters the transcriptome and chromatin accessibility of stromal progenitors, resulting in hyperactivation of Wnt signaling. The impacts of mutant ENL on both nephron and stroma lineages lead to profound kidney developmental defects and postnatal mortality in mice. Notably, a small molecule inhibiting mutant ENL's histone acetylation binding activity largely reverses these defects. This study provides insights into how mutations in epigenetic regulators disrupt kidney development and suggests a potential therapeutic approach.


Assuntos
Diferenciação Celular , Rim , Mutação , Análise de Célula Única , Animais , Camundongos , Rim/metabolismo , Rim/patologia , Diferenciação Celular/genética , Regulação da Expressão Gênica no Desenvolvimento , Cromatina/metabolismo , Epigênese Genética , Tumor de Wilms/genética , Tumor de Wilms/patologia , Tumor de Wilms/metabolismo , Histonas/metabolismo , Acetilação , Humanos , Organogênese/genética , Via de Sinalização Wnt/genética , Néfrons/metabolismo , Néfrons/patologia , Néfrons/embriologia , Transcriptoma/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Feminino , Masculino , Multiômica
2.
J Am Chem Soc ; 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38859684

RESUMO

Reducing iridium (Ir) catalyst loading for acidic oxygen evolution reaction (OER) is a critical strategy for large-scale hydrogen production via proton exchange membrane (PEM) water electrolysis. However, simultaneously achieving high activity, long-term stability, and reduced material cost remains challenging. To address this challenge, we develop a framework by combining density functional theory (DFT) prediction using model surfaces and proof-of-concept experimental verification using thin films and nanoparticles. DFT results predict that oxidized Ir monolayers over titanium nitride (IrOx/TiN) should display higher OER activity than IrOx while reducing Ir loading. This prediction is verified by depositing Ir monolayers over TiN thin films via physical vapor deposition. The promising thin film results are then extended to commercially viable powder IrOx/TiN catalysts, which demonstrate a lower overpotential and higher mass activity than commercial IrO2 and long-term stability of 250 h to maintain a current density of 10 mA cm-2. The superior OER performance of IrOx/TiN is further confirmed using a proton exchange membrane water electrolyzer (PEMWE), which shows a lower cell voltage than commercial IrO2 to achieve a current density of 1 A cm-2. Both DFT and in situ X-ray absorption spectroscopy reveal that the high OER performance of IrOx/TiN strongly depends on the IrOx-TiN interaction via direct Ir-Ti bonding. This study highlights the importance of close interaction between theoretical prediction based on mechanistic understanding and experimental verification based on thin film model catalysts to facilitate the development of more practical powder IrOx/TiN catalysts with high activity and stability for acidic OER.

3.
Cell Rep ; 43(6): 114323, 2024 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-38861385

RESUMO

Aberrant male germline development can lead to the formation of seminoma, a testicular germ cell tumor. Seminomas are biologically similar to primordial germ cells (PGCs) and many bear an isochromosome 12p [i(12p)] with two additional copies of the short arm of chromosome 12. By mapping seminoma transcriptomes and open chromatin landscape onto a normal human male germline trajectory, we find that seminoma resembles premigratory/migratory PGCs; however, it exhibits enhanced germline and pluripotency programs and upregulation of genes involved in apoptosis, angiogenesis, and MAPK/ERK pathways. Using pluripotent stem cell-derived PGCs from Pallister-Killian syndrome patients mosaic for i(12p), we model seminoma and identify gene dosage effects that may contribute to transformation. As murine seminoma models do not exist, our analyses provide critical insights into genetic, cellular, and signaling programs driving seminoma transformation, and the in vitro platform developed herein permits evaluation of additional signals required for seminoma tumorigenesis.


Assuntos
Epigênese Genética , Células Germinativas , Seminoma , Neoplasias Testiculares , Humanos , Seminoma/genética , Seminoma/patologia , Seminoma/metabolismo , Masculino , Células Germinativas/metabolismo , Neoplasias Testiculares/genética , Neoplasias Testiculares/patologia , Neoplasias Testiculares/metabolismo , Transcrição Gênica , Regulação Neoplásica da Expressão Gênica , Transcriptoma/genética
4.
bioRxiv ; 2024 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-38766219

RESUMO

Cell differentiation during organogenesis relies on precise epigenetic and transcriptional control. Disruptions to this regulation can result in developmental abnormalities and malignancies, yet the underlying mechanisms are not well understood. Wilms tumors, a type of embryonal tumor closely linked to disrupted organogenesis, harbor mutations in epigenetic regulators in 30-50% of cases. However, the role of these regulators in kidney development and pathogenesis remains unexplored. By integrating mouse modeling, histological characterizations, and single-cell transcriptomics and chromatin accessibility profiling, we show that a Wilms tumor-associated mutation in the chromatin reader protein ENL disrupts kidney development trajectory by rewiring the gene regulatory landscape. Specifically, the mutant ENL promotes the commitment of nephron progenitors while simultaneously restricting their differentiation by dysregulating key transcription factor regulons, particularly the HOX clusters. It also induces the emergence of abnormal progenitor cells that lose their chromatin identity associated with kidney specification. Furthermore, the mutant ENL might modulate stroma-nephron interactions via paracrine Wnt signaling. These multifaceted effects caused by the mutation result in severe developmental defects in the kidney and early postnatal mortality in mice. Notably, transient inhibition of the histone acetylation binding activity of mutant ENL with a small molecule displaces transcriptional condensates formed by mutant ENL from target genes, abolishes its gene activation function, and restores developmental defects in mice. This work provides new insights into how mutations in epigenetic regulators can alter the gene regulatory landscape to disrupt kidney developmental programs at single-cell resolution in vivo . It also offers a proof-of-concept for the use of epigenetics-targeted agents to rectify developmental defects.

5.
J Am Chem Soc ; 146(5): 3010-3022, 2024 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-38278519

RESUMO

The development of Pt-based catalysts for use in fuel cells that meet performance targets of high activity, maximized stability, and low cost remains a huge challenge. Herein, we report a nitrogen (N)-doped high-entropy alloy (HEA) electrocatalyst that consists of a Pt-rich shell and a N-doped PtCoFeNiCu core on a carbon support (denoted as N-Pt/HEA/C). The N-Pt/HEA/C catalyst showed a high mass activity of 1.34 A mgPt-1 at 0.9 V for the oxygen reduction reaction (ORR) in rotating disk electrode (RDE) testing, which substantially outperformed commercial Pt/C and most of the other binary/ternary Pt-based catalysts. The N-Pt/HEA/C catalyst also demonstrated excellent stability in both RDE and membrane electrode assembly (MEA) testing. Using operando X-ray absorption spectroscopy (XAS) measurements and theoretical calculations, we revealed that the enhanced ORR activity of N-Pt/HEA/C originated from the optimized adsorption energy of intermediates, resulting in the tailored electronic structure formed upon N-doping. Furthermore, we showed that the multiple metal-nitrogen bonds formed synergistically improved the corrosion resistance of the 3d transition metals and enhanced the ORR durability.

6.
PLoS Genet ; 19(12): e1011080, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-38091369

RESUMO

Despite our increasing knowledge of molecular mechanisms guiding various aspects of human reproduction, those underlying human primordial germ cell (PGC) development remain largely unknown. Here, we conducted custom CRISPR screening in an in vitro system of human PGC-like cells (hPGCLCs) to identify genes required for acquisition and maintenance of PGC fate. Amongst our candidates, we identified TCL1A, an AKT coactivator. Functional assessment in our in vitro hPGCLCs system revealed that TCL1A played a critical role in later stages of hPGCLC development. Moreover, we found that TCL1A loss reduced AKT-mTOR signaling, downregulated expression of genes related to translational control, and subsequently led to a reduction in global protein synthesis and proliferation. Together, our study highlights the utility of CRISPR screening for human in vitro-derived germ cells and identifies novel translational regulators critical for hPGCLC development.


Assuntos
Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Proteínas Proto-Oncogênicas c-akt , Humanos , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Diferenciação Celular/genética , Células Germinativas/metabolismo , Transcriptoma
7.
Alzheimers Res Ther ; 15(1): 212, 2023 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-38087316

RESUMO

BACKGROUND: Developing a screening method for identifying individuals at higher risk of elevated brain amyloid burden is important to reduce costs and burden to patients in clinical trials on Alzheimer's disease or the clinical setting. We developed machine learning models using objectively measured lifestyle factors to predict elevated brain amyloid burden on positron emission tomography. METHODS: Our prospective cohort study of non-demented, community-dwelling older adults aged ≥ 65 years was conducted from August 2015 to September 2019 in Usuki, Oita Prefecture, Japan. One hundred and twenty-two individuals with mild cognitive impairment or subjective memory complaints (54 men and 68 women, median age: 75.50 years) wore wearable sensors and completed self-reported questionnaires, cognitive test, and positron emission tomography imaging at baseline. Moreover, 99 individuals in the second year and 61 individuals in the third year were followed up. In total, 282 eligible records with valid wearable sensors, cognitive test results, and amyloid imaging and data on demographic characteristics, living environments, and health behaviors were used in the machine learning models. Amyloid positivity was defined as a standardized uptake value ratio of ≥ 1.4. Models were constructed using kernel support vector machine, Elastic Net, and logistic regression for predicting amyloid positivity. The mean score among 10 times fivefold cross-validation repeats was utilized for evaluation. RESULTS: In Elastic Net, the mean area under the receiver operating characteristic curve of the model using objectively measured lifestyle factors alone was 0.70, whereas that of the models using wearable sensors in combination with demographic characteristics and health and life environment questionnaires was 0.79. Moreover, 22 variables were common to all machine learning models. CONCLUSION: Our machine learning models are useful for predicting elevated brain amyloid burden using readily-available and noninvasive variables without the need to visit a hospital. TRIAL REGISTRATION: This prospective study was conducted in accordance with the Declaration of Helsinki and was approved by the local ethics committee of Oita University Hospital (UMIN000017442). A written informed consent was obtained from all participants. This research was performed based on the Strengthening the Reporting of Observational Studies in Epidemiology reporting guideline.


Assuntos
Doença de Alzheimer , Disfunção Cognitiva , Dispositivos Eletrônicos Vestíveis , Masculino , Humanos , Feminino , Idoso , Estudos Prospectivos , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/psicologia , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Tomografia por Emissão de Pósitrons , Amiloide/metabolismo , Disfunção Cognitiva/diagnóstico por imagem , Disfunção Cognitiva/psicologia , Proteínas Amiloidogênicas , Estilo de Vida , Aprendizado de Máquina , Peptídeos beta-Amiloides/metabolismo
8.
Development ; 150(17)2023 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-37650565

RESUMO

Male germ cells undergo a complex sequence of developmental events throughout fetal and postnatal life that culminate in the formation of haploid gametes: the spermatozoa. Errors in these processes result in infertility and congenital abnormalities in offspring. Male germ cell development starts when pluripotent cells undergo specification to sexually uncommitted primordial germ cells, which act as precursors of both oocytes and spermatozoa. Male-specific development subsequently occurs in the fetal testes, resulting in the formation of spermatogonial stem cells: the foundational stem cells responsible for lifelong generation of spermatozoa. Although deciphering such developmental processes is challenging in humans, recent studies using various models and single-cell sequencing approaches have shed new insight into human male germ cell development. Here, we provide an overview of cellular, signaling and epigenetic cascades of events accompanying male gametogenesis, highlighting conserved features and the differences between humans and other model organisms.


Assuntos
Células-Tronco Germinativas Adultas , Células Germinativas , Masculino , Humanos , Espermatozoides , Oócitos , Diferenciação Celular
9.
J Am Chem Soc ; 145(34): 19076-19085, 2023 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-37606196

RESUMO

Efficient C-C bond cleavage and oxidation of alcohols to CO2 is the key to developing highly efficient alcohol fuel cells for renewable energy applications. In this work, we report the synthesis of core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs as an active catalyst to effectively oxidize alcohols to CO2. The catalytic oxidation reaction is dependent on the Au/Pt ratios, and the Au1.0/Pt0.2 NWs have the largest percentage (∼75%) of stepped Au/Pt sites and show the highest activity for ethanol electro-oxidation, reaching an unprecedented 196.9 A/mgPt (32.5 A/mgPt+Au). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as methanol, n-propanol, and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy are used to characterize the catalyst structure and to identify key reaction intermediates, providing concrete evidence that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to catalyze the alcohol oxidation reaction, which is further supported by DFT calculations that the C-C bond cleavage is indeed enhanced on the undercoordinated Pt-Au surface. Our study provides important evidence that a core/shell structure with stepped core/shell sites is essential to enhance electrochemical oxidation of alcohols and will also be central to understanding electro-oxidation reactions and to the future development of highly efficient direct alcohol fuel cells for renewable energy applications.

10.
Mol Cell Endocrinol ; 573: 111949, 2023 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-37201564

RESUMO

Male and female germ cells undergo genome-wide reprogramming during their development, and execute sex-specific programs to complete meiosis and successfully generate healthy gametes. While sexually dimorphic germ cell development is fundamental, similarities and differences exist in the basic processes governing normal gametogenesis. At the simplest level, male gamete generation in mammals is centred on the activity of spermatogonial stem cells (SSCs), and an equivalent cell state is not present in females. Maintaining this unique SSC epigenetic state, while keeping to germ cell-intrinsic developmental programs, poses challenges for the correct completion of spermatogenesis. In this review, we highlight the origins of spermatogonia, comparing and contrasting them with female germline development to emphasize specific developmental processes that are required for their function as germline stem cells. We identify gaps in our current knowledge about human SSCs and further discuss the impact of the unique regulation of the sex chromosomes during spermatogenesis, and the roles of X-linked genes in SSCs.


Assuntos
Epigênese Genética , Espermatogênese , Animais , Feminino , Masculino , Humanos , Espermatogênese/genética , Espermatogônias/fisiologia , Diferenciação Celular , Cromossomos Sexuais/genética , Células-Tronco/fisiologia , Testículo , Mamíferos/genética
11.
Methods Mol Biol ; 2656: 145-159, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37249870

RESUMO

There is a scarcity of information regarding the molecular mechanisms underlying human germ cell development due to limitations in obtaining the relevant materials. Reconstitution of human germ cell development from pluripotent stem cells in vitro would provide critical insight into the etiology of various reproductive conditions and disorders, including infertility.Recently, we reported the in vitro reconstitution of human prospermatogonial development from human-induced pluripotent stem cells through human primordial germ cell (PGC)-like cells (hPGCLCs) using long-term cultured xenogeneic reconstituted testes. Here, we describe a method to generate M-prospermatogonia-like cells (MLCs) and T1-prospermatogonia-like cells (T1LCs), which closely resemble M- and T1-prospermatogonia present in second-trimester human fetal testes in vivo.


Assuntos
Células-Tronco Pluripotentes Induzidas , Células-Tronco Pluripotentes , Masculino , Humanos , Células Germinativas , Diferenciação Celular , Testículo
12.
ACS Nano ; 17(4): 3492-3505, 2023 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-36753696

RESUMO

Designing N-coordinated porous single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) is a promising approach to achieve enhanced energy conversion due to maximized atom utilization and higher activity. Here, we report two Co(II)-porphyrin/ [2,1,3]-benzothiadiazole (BTD)-based covalent organic frameworks (COFs; Co@rhm-PorBTD and Co@sql-PorBTD), which are efficient SAC systems for O2 electrocatalysis (ORR). Experimental results demonstrate that these two COFs outperform the mass activity (at 0.85 V) of commercial Pt/C (20%) by 5.8 times (Co@rhm-PorBTD) and 1.3 times (Co@sql-PorBTD), respectively. The specific activities of Co@rhm-PorBTD and Co@sql-PorBTD were found to be 10 times and 2.5 times larger than that of Pt/C, respectively. These COFs also exhibit larger power density and recycling stability in Zn-air batteries compared with a Pt/C-based air cathode. A theoretical analysis demonstrates that the combination of Co-porphyrin with two different BTD ligands affords two crystalline porous electrocatalysts having different d-band center positions, which leads to reactivity differences toward alkaline ORR. The strategy, design, and electrochemical performance of these two COFs offer a pyrolysis-free bottom-up approach that avoids the creation of random atomic sites, significant metal aggregation, or unpredictable structural features.

13.
Elife ; 122023 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-36719274

RESUMO

Reconstitution of germ cell fate from pluripotent stem cells provides an opportunity to understand the molecular underpinnings of germ cell development. Here, we established robust methods for induced pluripotent stem cell (iPSC) culture in the common marmoset (Callithrix jacchus [cj]), allowing stable propagation in an undifferentiated state. Notably, iPSCs cultured on a feeder layer in the presence of a WNT signaling inhibitor upregulated genes related to ubiquitin-dependent protein catabolic processes and enter a permissive state that enables differentiation into primordial germ cell-like cells (PGCLCs) bearing immunophenotypic and transcriptomic similarities to pre-migratory cjPGCs in vivo. Induction of cjPGCLCs is accompanied by transient upregulation of mesodermal genes, culminating in the establishment of a primate-specific germline transcriptional network. Moreover, cjPGCLCs can be expanded in monolayer while retaining the germline state. Upon co-culture with mouse testicular somatic cells, these cells acquire an early prospermatogonia-like phenotype. Our findings provide a framework for understanding and reconstituting marmoset germ cell development in vitro, thus providing a comparative tool and foundation for a preclinical modeling of human in vitro gametogenesis.


Assuntos
Células-Tronco Pluripotentes Induzidas , Células-Tronco Pluripotentes , Animais , Camundongos , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Callithrix , Diferenciação Celular , Células-Tronco Pluripotentes/metabolismo , Células Germinativas/metabolismo
14.
Dev Cell ; 57(22): 2566-2583.e8, 2022 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-36413950

RESUMO

The mechanisms leading to adrenal cortex development and steroid synthesis in humans remain poorly understood due to the paucity of model systems. Herein, we recapitulate human fetal adrenal cortex specification processes through stepwise induction of human-induced pluripotent stem cells through posterior intermediate mesoderm-like and adrenocortical progenitor-like states to ultimately generate fetal zone adrenal-cortex-like cells (FZLCs), as evidenced by histomorphological, ultrastructural, and transcriptome features and adrenocorticotropic hormone (ACTH)-independent Δ5 steroid biosynthesis. Furthermore, FZLC generation is promoted by SHH and inhibited by NOTCH, ACTIVIN, and WNT signaling, and steroid synthesis is amplified by ACTH/PKA signaling and blocked by inhibitors of Δ5 steroid synthesis enzymes. Finally, NR5A1 promotes FZLC survival and steroidogenesis. Together, these findings provide a framework for understanding and reconstituting human adrenocortical development in vitro, paving the way for cell-based therapies of adrenal insufficiency.


Assuntos
Córtex Suprarrenal , Células-Tronco Pluripotentes Induzidas , Humanos , Via de Sinalização Wnt , Hormônio Adrenocorticotrópico , Esteroides
15.
Healthcare (Basel) ; 10(9)2022 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-36141238

RESUMO

The human gastrointestinal tract, which constitutes the digestive system, contains a large number of virus particles that maintain organizational homeostasis and health. Conversely, viral pathogens have also attracted attention for their involvement in the pathogenesis of certain cancers, including gastrointestinal cancers. To aid prevention and treatment of these cancers, the relevance of gastrointestinal viral factors as potential risk factors needs to be carefully investigated. This review summarizes and discusses the available literature on the relationship between the development of esophageal, gastric, and colorectal cancers and their corresponding viruses. This review reveals that research on the association between colorectal cancer and viruses, in particular, is still in its infancy compared to the association between HPV and esophageal cancer and between EBV and gastric cancer.

16.
ACS Appl Mater Interfaces ; 14(27): 30914-30926, 2022 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-35759361

RESUMO

Herein, we investigate the effect of the chemical composition of double perovskite nanorods on their versatile electrocatalytic activity not only as supports for the oxidation of small organic molecules but also as catalysts for the oxygen evolution reaction. Specifically, Y2CoMnO6 and Y2NiMnO6 nanorods with average diameters of 300 nm were prepared by a two-step hydrothermal method, in which the individual effects of synthetic parameters, such as the pH, annealing temperature, and precursor ratios on both the composition and morphology, were systematically investigated. When used as supports for Pt nanoparticles, Y2CoMnO6/Pt catalysts exhibited an electrocatalytic activity for the methanol oxidation reaction, which is 2.1 and 1.3 times higher than that measured for commercial Pt/C and Y2NiMnO6/Pt, respectively. Similarly, the Co-based catalyst support material displayed an ethanol oxidation activity, which is 2.3 times higher than both Pt/C and Y2NiMnO6/Pt. This clear enhancement in the activity for Y2CoMnO6 can largely be attributed to strong metal-support interactions, as evidenced by a downshift in the binding energy of the Pt 4f bands, measured by X-ray photoelectron spectroscopy (XPS), which is often correlated not only with a downshift in the d-band center but also to a decreased adsorption of poisoning adsorbates. Moreover, when used as catalysts for the oxygen evolution reaction, Y2CoMnO6 displayed a much greater activity as compared with Y2NiMnO6. This behavior can largely be attributed not only to a preponderance of comparatively more favorable oxidation states and electronic configurations but also to the formation of an active layer on the surface of the Y2CoMnO6 catalyst, which collectively gives rise to improved performance metrics and greater stability as compared with both IrO2 and Y2NiMnO6. Overall, these results highlight the importance of both the chemical composition and the electronic structure of double perovskites, especially when utilized in multifunctional roles as either supports or catalysts.

17.
Artigo em Inglês | MEDLINE | ID: mdl-35666990

RESUMO

PtM (M = 3d transition metals) alloys are known as the promising oxygen reduction reaction catalysts and have been considered as the replacement of pure Pt catalysts for the commercialization of proton exchange membrane fuel cells. Although great progress has been made in the past three decades, the performance and durability of PtM catalysts still face stringent challenges from practical applications. Functionalization of a catalyst carbon support with nitrogen-contained groups can add charges onto its surface, which can be utilized to build a more complete ionomer/catalyst interface, to reduce the catalyst particle size, and to improve particle size distribution. Nitriding of PtNi catalysts can effectively improve the catalyst activity and stability by the modification of lattice strain. Hereby, we propose a synergistic approach of combining polybenzimidazole-grafted Vulcan XC72 carbon as the catalyst carbon support and the nitriding of PtNi to develop PtNiN/XC72-polybenzimidazole catalysts. Such PtNiN/XC72-PBI catalysts exhibit the excellent performance of fuel cell membrane electrode assembly (i.e., mass activity, 440 mA mgPt-1; electrochemical surface area, 51 m2 gPt-1; and rated power density, 836 mW cm-2) as well as promising catalyst stability. The developed PtNiN/XC72-PBI meets the US DOE 2020 targets of mass activity for the fuel cell catalysts. This work provides a novel approach and a promising pathway on the development of the catalyst using such a synergistic approach─modification of the catalyst structure by nitrogen doping and functionalization of carbon support by polybenzimidazole for both high performance and high durability.

18.
Genes Dev ; 36(11-12): 752-763, 2022 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-35738678

RESUMO

Self-renewal of spermatogonial stem cells is vital to lifelong production of male gametes and thus fertility. However, the underlying mechanisms remain enigmatic. Here, we show that DOT1L, the sole H3K79 methyltransferase, is required for spermatogonial stem cell self-renewal. Mice lacking DOT1L fail to maintain spermatogonial stem cells, characterized by a sequential loss of germ cells from spermatogonia to spermatids and ultimately a Sertoli cell only syndrome. Inhibition of DOT1L reduces the stem cell activity after transplantation. DOT1L promotes expression of the fate-determining HoxC transcription factors in spermatogonial stem cells. Furthermore, H3K79me2 accumulates at HoxC9 and HoxC10 genes. Our findings identify an essential function for DOT1L in adult stem cells and provide an epigenetic paradigm for regulation of spermatogonial stem cells.


Assuntos
Histona-Lisina N-Metiltransferase/metabolismo , Espermatogônias , Células-Tronco , Animais , Diferenciação Celular , Masculino , Camundongos , Espermatogônias/citologia , Espermatogônias/metabolismo , Células-Tronco/citologia , Células-Tronco/metabolismo
19.
PLoS Genet ; 18(5): e1009846, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35551519

RESUMO

Mammalian germ cells stem from primordial germ cells (PGCs). Although the gene regulatory network controlling the development of germ cells such as PGCs is critical for ensuring gamete integrity, substantial differences exist in this network among mammalian species, suggesting that this network has been modified during mammalian evolution. Here, we show that a hominoid-specific group of endogenous retroviruses, LTR5_Hs, discloses enhancer-like signatures in human in vitro-induced PGCs, PGC-like cells (PGCLCs). Human PGCLCs exhibit a transcriptome signature similar to that of naïve-state pluripotent cells. LTR5_Hs are epigenetically activated in both PGCLCs and naïve pluripotent cells, and the expression of genes in the vicinity of LTR5_Hs is coordinately upregulated in these cell types, contributing to the establishment of the transcriptome similarity between these cell types. LTR5_Hs are preferentially bound by transcription factors that are highly expressed in both PGCLCs and naïve pluripotent cells (KLF4, TFAP2C, NANOG, and CBFA2T2), suggesting that these transcription factors contribute to the epigenetic activation of LTR5_Hs in these cells. Comparative transcriptome analysis between humans and macaques suggests that the expression of many genes in PGCLCs and naïve pluripotent cells is upregulated by LTR5_Hs insertions in the hominoid lineage. Together, this study suggests that LTR5_Hs insertions may have finetuned the gene regulatory network shared between PGCLCs and naïve pluripotent cells and coordinately altered the gene expression in these cells during hominoid evolution.


Assuntos
Retrovirus Endógenos , Animais , Diferenciação Celular/genética , Retrovirus Endógenos/genética , Redes Reguladoras de Genes/genética , Células Germinativas/metabolismo , Mamíferos/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
20.
Nat Commun ; 13(1): 2207, 2022 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-35459865

RESUMO

Reversible protonic ceramic electrochemical cells (R-PCECs) are ideally suited for efficient energy storage and conversion; however, one of the limiting factors to high performance is the poor stability and insufficient electrocatalytic activity for oxygen reduction and evolution of the air electrode exposed to the high concentration of steam. Here we report our findings in enhancing the electrochemical activity and durability of a perovskite-type air electrode, Ba0.9Co0.7Fe0.2Nb0.1O3-δ (BCFN), via a water-promoted surface restructuring process. Under properly-controlled operating conditions, the BCFN electrode is naturally restructured to an Nb-rich BCFN electrode covered with Nb-deficient BCFN nanoparticles. When used as the air electrode for a fuel-electrode-supported R-PCEC, good performances are demonstrated at 650 °C, achieving a peak power density of 1.70 W cm-2 in the fuel cell mode and a current density of 2.8 A cm-2 at 1.3 V in the electrolysis mode while maintaining reasonable Faradaic efficiencies and promising durability.

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