Biology subjects

You, H.

Publications and source records attributed to You, H..

24 records · Page 2Linked to original sources

bioRxiv2021

METTL3 facilitates hepatic fibrosis progression via m6A-YTHDF2 dependent silencing of GPR161

Hepatic fibrosis (HF) is a very common condition seen in millions of patients with various liver diseases. N6-methyladenosine (m6A) plays critical roles in various biological and pathological processes. However, the role of m6A and its main methyltransferase METTL3 in HF remains obscure. Here, we reported that METTL3 expression was elevated in HSCs from CCl4 induced fibrotic liver. METTL3 knockdown in HSCs mediated by recombinant adeno-associated-virus serotype 9 packed short hairpin RNA against METTL3 alleviated liver injury and fibrosis compared to empty carrier group. Mechanistically, the decreased liver fibrosis in CCl4-treated HSC-specific METTL3 knockdown mice was due to the increased GPR161 that is a suppressor of Hedgehog pathway, a well-known pathway to activate in liver injury and regeneration. As expect, GPR161 transferred into HSCs alleviated liver fibrosis and HSC activation. Forced GPR161 expression inhibited Gli3 activated form nuclear accumulation and subsequently suppressed fibrosis-associate gene expression. Conclusion, HSC-specific deletion of METTL3 inhibits liver fibrosis via elevated GPR161 expression, which subsequently suppressed Hedgehog pathway activation and fibrosis-associated genes expression, providing novel therapeutic targets for HF therapy. Synopsis O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/472749v1_ufig1.gif" ALT="Figure 1"> View larger version (78K): org.highwire.dtl.DTLVardef@1245f3aorg.highwire.dtl.DTLVardef@e7effdorg.highwire.dtl.DTLVardef@13ce319org.highwire.dtl.DTLVardef@61be8b_HPS_FORMAT_FIGEXP M_FIG C_FIG The role of RNA m6A methyltransferase METTL3 in the progression of hepatic fibrosis is unclear. Here, we reveal that suppresses m6A modification by depletion of METTL3 in Hepatic Stellate Cells (HSCs), stabilizes the GPR161 transcripts, that involved in suppressing Hedgehog signaling pathway, through YTHDF2, thereby alleviating the fibrosis feature of CCl4-induced liver injury. O_LIDisruption of m6A methyltransferases METTL3 in HSCs alleviates liver fibrosis feature. C_LIO_LIMETTL3 depletion in liver HSCs suppresses its activation by suppressing Hedgehog signaling pathway through stabilizing GPR161 transcripts in an m6A-YTHDF2 dependent manner. C_LIO_LIGPR161 activates PKA that mediates phosphorylation and degradation of full-length Gli3 (Gli3-FL) protein, then the short Gli3 (Gli3-R) translocated into the nucleus and suppresses the fibrosis associated gene transcription. C_LIO_LIThe elevated METTL3 expression is attribute to its promoter H3K27ac modification. C_LI

molecular biology↗

bioRxiv2020

MoCpa1-mediated arginine biosynthesis is crucial for fungal growth, conidiation, and plant infection of Magnaporthe oryzae

Arginine is an important amino acid involved in processes such as cell signal transduction, protein synthesis, and sexual reproduction. To understand the biological roles of arginine biosynthesis in pathogenic fungi, we used Cpa1, the carbamoyl phosphate synthase arginine-specific small chain subunit in Saccharomyces cerevisiae as a query to identify its ortholog in Magnaporthe oryzae genome database and named it MoCpa1. MoCpa1 is a 471-amino acid protein containing the CPSase_sm_chain domain and the GATase domain. MoCpa1 transcripts were highly expressed at the conidiation, early-infection, and late-infection stages of the fungus. Targeted deletion of MoCPA1 gene resulted in the {Delta}Mocpa1 mutant exhibiting arginine auxotrophy on MM, confirming its role in de novo arginine biosynthesis. The {Delta}Mocpa1 mutant presented significantly decreased sporulation with some of its conidia being defective in morphology. Furthermore, the {Delta}Mocpa1 mutant was nonpathogenic on rice and barley leaves, which was a result of defects in appressorium-mediated penetration and restricted invasive hyphal growth within host cells. Addition of exogenous arginine partially rescued conidiation and pathogenicity defects on the barley and rice leaves, while introduction of MoCPA1 gene in {Delta}Mocpa1 mutant fully complemented the lost phenotype. Further confocal microscopy examination revealed that MoCpa1 is localized in the mitochondria. In summary, our results demonstrate that MoCpa1-mediated arginine biosynthesis is crucial for fungal development, conidiation, appressorium formation and infection-related morphogenesis in M. oryzae, thus serving as an attractive target for mitigating obstinate fungal plant pathogens.

molecular biology↗

bioRxiv2020

Repopulating Kupffer Cells Originate Directly from Hematopoietic Stem Cells

Kupffer cells (KCs) originate from yolk sac progenitors before birth. Throughout adulthood, they self-maintain independently from the input of circulating monocytes (MOs) at stead state, and are replenished within 2 weeks after having been depleted, but the origin of repopulating KCs in adult remains unclear. The current paradigm dictates that repopulating KCs originate from preexisting KCs or monocytes, but there remains a lack of fate-mapping evidence. In current study, we firstly traced the fate of preexisting KCs and that of monocytic cells with tissue-resident macrophage-specific and monocytic cell-specific fate mapping mouse models, respectively, and found no evidences that repopulating KCs originate from preexisting KCs or MOs. Secondly, we performed genetic lineage tracing to determine the type of progenitor cells involved in response to KC depletion in mice, and found that in response to KC depletion, hematopoietic stem cells (HSCs) proliferated in the bone marrow, mobilized into the blood, adoptively transferred into the liver and differentiated into KCs. Finally, we traced the fate of HSCs in a HSC-specific fate-mapping mouse model, in context of chronic liver inflammation induced by repeated carbon tetrachloride treatment, and confirmed that repopulating KCs originated directly from HSCs. Taken together, these findings provided strong in vivo fate-mapping evidences that repopulating KCs originate directly from Hematopoietic stem cells not from preexisting KCs or from MOs. SignificanceThere is a standing controversy in the field regarding the cellular origin of repopulating macrophages. This paper provides strong in vivo fate-mapping evidences that repopulating KCs originate directly from hematopoietic stem cells not from preexisting KCs or from MOs, which presenting a completely novel understanding of the cellular origin of repopulating Kupffer Cells and shedding light on the divergent roles of KCs in liver homeostasis and diseases.

cell biology↗

bioRxiv2020

Inhibiting proBDNF to mature BDNF conversion leads to autism-like phenotypes in vivo

Autism spectrum disorders (ASD) comprise a range of early age-onset neurodevelopment disorders with genetic heterogeneity. Most ASD related genes are involved in synaptic function, which is oppositely regulated by brain-derived neurotrophic factor (BDNF): the precursor proBDNF inhibits while mature BDNF (mBDNF) potentiates synapses. Here we generated a knock-in mouse line (BDNFmet/leu) in which the conversion of proBDNF to mBDNF is inhibited. Biochemical experiments revealed residual mBDNF but excessive proBDNF in the brain. Similar to other ASD mouse models, the BDNFmet/leu mice showed decreased brain volumes, reduced dendritic arborization, altered spines, and impaired synaptic transmission and plasticity. They also exhibited ASD-like phenotypes, including stereotypical behaviors, deficits in social interaction, hyperactivity, and elevated stress response. Interestingly, the plasma level of proBDNF, but not mBDNF, was significantly elevated in ASD patients. These results suggest that proBDNF level, but not Bdnf gene, is associated with autism-spectrum behaviors, and identify a potential blood marker and therapeutic target for ASD.

neuroscience↗

bioRxiv2018

The holdase function of Escherichia coli Hsp70 (DnaK) chaperone

In Escherichia coli, the DnaK/DnaJ/GrpE system plays a critical role in mediating protein refolding and buffering against protein aggregation due to environmental stress. The underlying mechanism remains unclear. In this work, we probe the activity of DnaK/DnaJ/GrpE system with single-molecule protein refolding assay using tandem repeats of titin immunoglobulin 27 (I27)8. We provide direct evidence that DnaK in apo- and ADP-bound state is predominantly a holdase, which kinetically stabilizes the polyprotein in its unfolded form. Binding of ATP relieves DnaKs holding, allowing protein refolding. The presence of co-chaperone DnaJ and GrpE modulates this holding-release switching, possibly by altering DnaKs nucleotide state. Our findings thus provide important insights to the molecular mechanism of DnaK/DnaJ/GrpE system.

molecular biology↗

bioRxiv2016

Long-range suppressive influences from the visual surround can be explained by anatomically plausible recruitment of local competition in a model of columnar cortex

Although neurons in columns of visual cortex of adult carnivores and primates share similar orientation tuning preferences, responses of nearby neurons are surprisingly sparse and temporally uncorrelated, especially in response to complex visual scenes. The mechanisms underlying this counter-intuitive combination of response properties are still unknown. Here we present a computational model of columnar visual cortex which explains experimentally observed integration of complex features across the visual field, and which is consistent with anatomical and physiological profiles of cortical excitation and inhibition. In this model, sparse local excitatory connections within columns, coupled with strong unspecific local inhibition and functionally-specific long-range excitatory connections across columns, give rise to competitive dynamics that reproduce experimental observations. Our results explain surround modulation of responses to simple and complex visual stimuli, including reduced correlation of nearby excitatory neurons, increased excitatory response selectivity, increased inhibitory selectivity, and complex orientation-tuning of surround modulation.

neuroscience↗