Search bioRxiv⌕ Search

Biology subjects

Liu, P.

Publications and source records attributed to Liu, P..

At least 199 records · Page 11Linked to original sources

Post-Transplant Administration of G-CSF Impedes Engraftment of Gene Edited Human Hematopoietic Stem Cells by Exacerbating the p53-Mediated DNA Damage Response

Granulocyte colony stimulating factor (G-CSF) is commonly used as adjunct treatment to hasten recovery from neutropenia following chemotherapy and autologous transplantation of hematopoietic stem and progenitor cells (HSPCs) for malignant disorders. However, the utility of G-CSF administration after ex vivo gene therapy procedures targeting human HSPCs has not been thoroughly evaluated. Here, we provide evidence that post-transplant administration of G-CSF impedes engraftment of CRISPR-Cas9 gene edited human HSPCs in xenograft models. G-CSF acts by exacerbating the p53-mediated DNA damage response triggered by Cas9- mediated DNA double-stranded breaks. Transient p53 inhibition in culture attenuates the negative impact of G-CSF on gene edited HSPC function. In contrast, post-transplant administration of G-CSF does not impair the repopulating properties of unmanipulated human HSPCs or HSPCs genetically engineered by transduction with lentiviral vectors. The potential for post-transplant G-CSF administration to aggravate HSPC toxicity associated with CRISPR-Cas9 gene editing should be considered in the design of ex vivo autologous HSPC gene editing clinical trials. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/547089v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1dae519org.highwire.dtl.DTLVardef@1f6ddacorg.highwire.dtl.DTLVardef@535cbaorg.highwire.dtl.DTLVardef@ecbeaf_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

Fluctuating selection facilitates the discovery of broadly effective but difficult to reach adaptive outcomes in yeast

Evolutionary compromises are thought to be common under fluctuating selection because the mutations that best enable adaptation to one environmental context can often be detrimental in others. Yet, prior experimental work has shown that generalists can sometimes perform as well as specialists in their own environments. Here we use a highly replicated evolutionary experiment (N = 448 asexual lineages of the brewers yeast) to show that even though fluctuation between two environmental conditions often induces evolutionary compromises (at least early on), it can also help reveal difficult to reach adaptive outcomes that ultimately improve performance in both environments. Specifically, we begin by showing that yeast adaptation to chemical stress can involve fitness tradeoffs with stress-free environments and that, accordingly, lineages that are repeatedly exposed to occasional stress tend to respond by trading performance for breadth of adaptation. We then show that on rare occasions, fluctuating selection leads to the evolution of no-cost generalists that can even outcompete constant selection specialists in their own environments. We propose that the discovery of these broader and more effective adaptive outcomes under fluctuating selection could be partially facilitated by changes in the adaptive landscape that result from having to deal with fitness tradeoffs across different environmental conditions. Overall, our findings indicate that reconciling the short- and long-term evolutionary consequences of fluctuating selection could significantly improve our understanding of the evolution of specialization and generalism.

evolutionary biology↗

Small Interactor of PKD2 (SIP), a novel PKD2-related single-pass transmembrane protein, is required for proteolytic processing and ciliary import of Chlamydomonas PKD2

In Chlamydomonas cilia, the ciliopathy-relevant TRP channel PKD2 is spatially compartmentalized into a distal region, in which PKD2 binds the axoneme and extracellular mastigonemes, and a smaller proximal region, in which PKD2 is more mobile and lacks mastigonemes. Here, we show that the two PKD2 regions are established early during cilia regeneration and increase in length as cilia elongate. In abnormally long cilia, only the distal region elongated whereas both regions adjusted in length during cilia shortening. In dikaryon rescue experiments, tagged PKD2 rapidly entered the proximal region of PKD2-deficient cilia whereas assembly of the distal region was hindered, suggesting that axonemal docking of PKD2 requires de novo ciliary assembly. We identified Small Interactor of PKD2 (SIP), a small PKD2-related protein, as a novel component of the PKD2-mastigoneme complex. In sip mutants, stability and proteolytic processing of PKD2 in the cell body were reduced and PKD2-mastigoneme complexes were absent from mutant cilia. Like the pkd2 and mst1 mutants, sip swims with reduced velocity. Cilia of the pkd2 mutant beat with normal frequency and bending pattern but were less efficient in moving cells supporting a passive role of the PKD2-SIP-mastigoneme complexes in increasing the effective surface of Chlamydomonas cilia.

cell biology↗

Neuropathy target esterase activity predicts retinopathy among PNPLA6 disorders

Biallelic pathogenic variants in the PNPLA6 gene cause a broad spectrum of disorders leading to gait disturbance, visual impairment, anterior hypopituitarism, and hair anomalies. PNPLA6 encodes Neuropathy target esterase (NTE), yet the role of NTE dysfunction on affected tissues in the large spectrum of associated disease remains unclear. We present a clinical meta-analysis of a novel cohort of 23 new patients along with 95 reported individuals with PNPLA6 variants that implicate missense variants as a driver of disease pathogenesis. Measuring esterase activity of 46 disease-associated and 20 common variants observed across PNPLA6-associated clinical diagnoses unambiguously reclassified 10 variants as likely pathogenic and 36 variants as pathogenic, establishing a robust functional assay for classifying PNPLA6 variants of unknown significance. Estimating the overall NTE activity of affected individuals revealed a striking inverse relationship between NTE activity and the presence of retinopathy and endocrinopathy. This phenomenon was recaptured in vivo in an allelic mouse series, where a similar NTE threshold for retinopathy exists. Thus, PNPLA6 disorders, previously considered allelic, are a continuous spectrum of pleiotropic phenotypes defined by an NTE genotype:activity:phenotype relationship. This relationship and the generation of a preclinical animal model pave the way for therapeutic trials, using NTE as a biomarker.

neuroscience↗

Cotyledon Peeling Method for Passion Fruit Protoplasts: a versatile cell system for transient gene expression in passion fruit (Passiflora edulis)

Passion fruit (Passiflora edulis) is a perennial evergreen vine that grows mainly in tropical and subtropical regions due to its nutritional, medicinal and ornamental values. However, the molecular biology study of passion fruit is extremely hindered by the lack of an easy and efficient method for transformation. The protoplast transformation system plays a vital role in plant regeneration, gene function analysis and genome editing. Here, we present a new method ( Cotyledon Peeling Method) for simple and efficient passion fruit protoplast isolation using cotyledon as the source tissue. A high yield (2.3 x 107 protoplasts per gram of fresh tissues) and viability (76%) of protoplasts were obtained upon incubation in the enzyme solution [1% (w/v) cellulase R10, 0.25% (w/v) macerozyme R10, 0.4 M mannitol, 10 mM CaCl2, 20 mM KCl, 20 mM MES and 0.1% (w/v) BSA, pH 5.7] for 2 hours. In addition, we achieved high transfection efficiency of 83% via the polyethylene glycol (PEG)-mediated transformation with a green fluorescent protein (GFP)-tagged plasmid upon optimization. The crucial factors affecting transformation efficiency were optimized as follows: 3 g of plasmid DNA, 5 min transfection time, PEG concentration at 40% and protoplast density of 100 x 104 cells/ml. Furthermore, the established protoplast system was successfully applied for subcellular localization analysis of multiple fluorescent organelle markers and protein-protein interaction study. Taken together, we report a simple and efficient passion fruit protoplast isolation and transformation system, and demonstrate its usage in transient gene expression for the first time in passion fruit. The protoplast system would provide essential support for various passion fruit biology studies, including genome editing, gene function analysis and whole plant regeneration.

plant biology↗

Identification of bioactive constituents for colitis from traditional Chinese medicine prescription via deep neural network

Colitis is a commonly encountered inflammatory disease in colon tissue, which can be triggered by various causes. Although traditional Chinese medicine (TCM) has been utilized for the treatment of colitis, it is still a great challenge to identify the major bioactive constituents and their modes of action among thousands of ingredients in TCM prescriptions. Inspired by the success of artificial intelligence and deep learning methods, we proposed a deep neural network (DNN) for TCM prescription recommendation. We constructed a graph-based DNN with 9,845 nodes and 161,950 edges, which integrated microscopic information including bioactive molecules, protein targets, and extracted features of prescriptions through feature embedding. A novel and efficient data augmentation strategy was implemented to expand the sample size based on 378 collected TCM prescriptions. Network pharmacology study revealed that the 10 most frequent ingredients in generated prescriptions were associated with multiple inflammatory signaling pathways. To verify the bioactive constituents in the generated prescriptions, 5 selected constituents were administrated to BALB/c mice with colitis. Suppressive effects of disease progression and pro-inflammatory factors comparable to sulfasalazin were observed with these compounds, revealing the effectiveness of our artificial intelligence strategy on idetification of bioactive constituents from TCM prescriptions.

bioinformatics↗

Identification of unique cytokine expressions in tumor immune microenvironment for various cancer types using single-cell RNA sequencing data via machine learning

Cytokines are small protein molecules that exhibit potent immunoregulatory properties, which are known as the essential components of the tumor immune microenvironment (TIME). While some cytokines are known to be universally upregulated in TIME, the unique cytokine expression patterns have not been fully resolved in specific types of cancers. To address this challenge, we develop a TIME single-cell RNA sequencing (scRNA-seq) dataset, which is designed to study cytokine expression patterns for precise cancer classification. The dataset, including 39 cancers, is constructed by integrating 695 tumor scRNA-seq samples from multiple public repositories. After screening and processing, the dataset retains only the expression data of immune cells. With a machine learning classification model, unique cytokine expression patterns are identified for various cancer categories and pioneering applied to cancer classification with an accuracy rate of 78.01%. Our method will not only boost the understanding of cancer-type-specific immune modulations in TIME but also serve as a crucial reference for future diagnostic and therapeutic research in cancer immunity.

bioinformatics↗

Hypoxia Bi-directionally Regulates Gut Vascular Barrier through HIF-1α-dependent Mechanism in vitro

ObjectiveThe gut vascular barrier (GVB) is the key checkpoint for pathogens to enter the blood circulation through the intestine, which is crucial for maintaining the intestinal barrier function. However, the effect and molecular mechanism of hypoxia on GVB remains unclear. Here, we show a role of the transcription factor hypoxia inducible factor-1 (HIF-1) in hypoxia-induced bi-directional regulation of GVB. Approach and ResultsAn in vitro GVB model composed of rat intestinal microvascular endothelial cells was studied. Evans blue-albumin efflux assay showed that the experimentally severe hypoxia induced by cobalt chloride (500 M, 24 h) markedly disrupted the GVB in vitro, while mild hypoxia induced by cobalt chloride (500 M, 6 h) evidently enhanced the GVB, revealing hypoxia-induced bi-directional regulation of the GVB for the first-time. Importantly, knockdown of HIF-1 largely abolished the bi-directional changes of GVB caused by hypoxia. Furthermore, experimentally severe hypoxia exacerbated the inflammatory GVB disruption induced by LPS or TNF-, while the mild hypoxia promoted the repair. ConclusionCollectively, our data indicate that hypoxia bi-directionally regulates GVB in a HIF-1-dependent manner.

cell biology↗

Gene editing without ex vivo culture evades genotoxicity in human hematopoietic stem cells

Gene editing the BCL11A erythroid enhancer is a validated approach to fetal hemoglobin (HbF) induction for {beta}-hemoglobinopathy therapy, though heterogeneity in edit allele distribution and HbF response may impact its safety and efficacy. Here we compared combined CRISPR-Cas9 endonuclease editing of the BCL11A +58 and +55 enhancers with leading gene modification approaches under clinical investigation. We found that combined targeting of the BCL11A +58 and +55 enhancers with 3xNLS-SpCas9 and two sgRNAs resulted in superior HbF induction, including in engrafting erythroid cells from sickle cell disease (SCD) patient xenografts, attributable to simultaneous disruption of core half E-box/GATA motifs at both enhancers. We corroborated prior observations that double strand breaks (DSBs) could produce unintended on- target outcomes in hematopoietic stem and progenitor cells (HSPCs) such as long deletions and centromere-distal chromosome fragment loss. We show these unintended outcomes are a byproduct of cellular proliferation stimulated by ex vivo culture. Editing HSPCs without cytokine culture bypassed long deletion and micronuclei formation while preserving efficient on-target editing and engraftment function. These results indicate that nuclease editing of quiescent hematopoietic stem cells (HSCs) limits DSB genotoxicity while maintaining therapeutic potency and encourages efforts for in vivo delivery of nucleases to HSCs.

genetics↗

Regulation of hippocampal mossy fiber-CA3 synapse function by a Bcl11b/C1ql2/Nrxn3(25b+) pathway

The transcription factor Bcl11b has been linked to neurodevelopmental and neuropsychiatric disorders associated with synaptic dysfunction. Bcl11b is highly expressed in dentate gyrus granule neurons and is required for the structural and functional integrity of mossy fiber-CA3 synapses. The underlying molecular mechanisms, however, remained unclear. We show that the synaptic organizer molecule C1ql2 is a direct functional target of Bcl11b that regulates synaptic vesicle recruitment and long-term potentiation at mossy fiber-CA3 synapses in vivo and in vitro. Furthermore, we demonstrate C1ql2 to exert its functions through direct interaction with a specific splice variant of neurexin-3, Nrxn3(25b+). Interruption of C1ql2-Nrxn3(25b+) interaction by expression of a non-binding C1ql2 mutant or by deletion of Nrxn3 in the dentate gyrus granule neurons recapitulates major parts of the Bcl11b as well as C1ql2 mutant phenotype. Together, this study identifies a novel C1ql2-Nrxn3(25b+)-dependent signaling pathway through which Bcl11b controls mossy fiber-CA3 synapse function. Thus, our findings contribute to the mechanistic understanding of neurodevelopmental disorders accompanied by synaptic dysfunction.

neuroscience↗

Chromatin and Gene Regulatory Dynamics of Optic Nerve Invasion in Retinoblastoma at Single-Cell Resolution

Retinoblastoma (RB), the most aggressive pediatric intraocular malignancy, urgently requires mechanistic insights to overcome limitations of current clinical interventions. Through integrated single-cell multi-omics analysis, we constructed a comprehensive epigenetic-transcriptomic atlas of photoreceptor subpopulations in RB. Pseudotemporal trajectory analysis revealed the differentiation cascade from retinal progenitor cells (RPCs) to malignant cone-like tumor cells (Cone-T), orchestrated by dynamic regulation of tumor suppressors (FEZ1) and oncogenic drivers (CITED2) within the MAPK pathway. Notably, we identified three photoreceptor subtype-specific transcription factors (EBF1, SOX15, NFIL3) exhibiting concordant overexpression and chromatin accessibility. Cell-cell communication analysis uncovered PPIA-BSG ligand-receptor interactions potentially driving tumor progression, while drug screening prioritized nine therapeutic candidates targeting transitional proliferative photoreceptors (P-p). Our findings establish a mechanistic framework for photoreceptor transformation and provide actionable targets for precision therapies.

cancer biology↗

SETDB1 Triple Tudor Domain Ligand, (R,R)-59, Promotes Methylation of Akt1 in Cells

Increased expression and hyperactivation of the methyltransferase SETDB1 are commonly observed in cancer and central nervous system disorders. However, there are currently no reported SETDB1-specific methyltransferase inhibitors in the literature, suggesting this is a challenging target. Here, we disclose that the previously reported small-molecule ligand for SETDB1s Triple Tudor Domain, (R,R)-59, is unexpectedly able to increase SETDB1 methyltransferase activity both in vitro and in cells. Specifically, (R,R)-59 promotes in vitro SETDB1-mediated methylation of lysine 64 of the protein kinase Akt1. Treatment with (R,R)-59 also increased Akt1 threonine 308 phosphorylation and activation, a known consequence of Akt1 methylation, resulting in stimulated cell proliferation in a dose-dependent manner. (R,R)-59 is the first SETDB1 small-molecule positive activator for the methyltransferase activity of this protein. Mechanism of action studies show that full-length SETDB1 is required for significant in vitro methylation of an Akt1-K64 peptide, and that this activity is stimulated by (R,R)-59 primarily through an increase in catalytic activity rather than a change in SAM binding. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=63 SRC="FIGDIR/small/539986v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@5f4022org.highwire.dtl.DTLVardef@16ba47borg.highwire.dtl.DTLVardef@1fb8b0borg.highwire.dtl.DTLVardef@16595bc_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

Spatially-resolved single-cell atlas of ascidian endostyle provides insights into the origin of vertebrate pharyngeal organs

The pharynx is an endoderm innovation in deuterostome ancestors, the vertebrate descendent structure of which is a pharyngeal developmental organizer involving multi-germ layer and organ derivatives. However, the evolutionary origination of complicated pharynx organs in vertebrates is still largely unknown. Endostyle, a transitional pharyngeal organ exclusively in basal chordates provides an opportunity to reveal the origin of pharyngeal organs. Here, utilizing cutting-edged Stereo-seq and single-cell RNA-seq, we constructed the first spatially-resolved single-cell atlas in the endostyle of urochordate ascidian Styela clava, where the spatial location of Stereo-seq and high capture efficiency of single-cell RNA-seq complement each other and identified 23 highly differentiated cell types. We identified a previously overlooked hemolymphoid region (HLR), which harbors immune and blood cell clusters with enriched stemness capacities, illuminating a mixed rudiment and stem-cell niches for the blood and lymphoid system. More excitingly, we discovered a mechanical-sensitive hair cell candidate in zone 3 homologous to vertebrate acoustico-lateralis system, which was supported by the expression of in situ hybridization-verified inner ear-specific markers, including PTPRQ, USH2A, WHRN, and ADGRV1, ultracellular structure evidence and cross-species comparison. These results thoroughly renewed the comprehension of the basal-chordate pharynx and provides expressional evidence for multiplexed pharyngeal organ evolution.

evolutionary biology↗

Vacuolar H+-ATPase subunit a was identified as the target protein of the oomycete inhibitor fluopicolide

Approximately 240 fungicides are currently in use. However, only a few direct targets have been identified, which limits the development of fungicides and rapid resistance monitoring. Fluopicolide, which is an excellent oomycete inhibitor, is classified as delocalization of spectrin-like proteins inhibitors by FRAC. In the current study, a Pc-actinin knockout had no effect on the sensitivity of Phytophthora capsici to fluopicolide. The vacuolar H+-ATPase subunit a (PcVHA-a) was identified using a BSA-seq and DARTS assay. Four kinds of point mutations in PcVHA-a that cause fluopicolide resistance in P. capsici were confirmed using site-directed mutagenesis. The results of MST, molecular docking, and a DARTS assay indicated that PcVHA-a could bind fluopicolide. Sequence analysis and a molecular docking assay proved the specificity of fluopicolide to oomycetes or fish. Our results suggest that PcVHA-a is the target of fluopicolide, and H+-ATPase could be used as a novel target for the development of new fungicides.

pharmacology and toxicology↗

Emergence of Emotion Selectivity in A Deep Neural Network Trained to Recognize Visual Objects

Recent neuroimaging studies have shown that the visual cortex plays an important role in representing the affective significance of visual input. The origin of these affect-specific visual representations is debated: they are intrinsic to the visual system versus they arise through reentry from frontal emotion processing structures such as the amygdala. We examined this problem by combining convolutional neural network (CNN) models of the human ventral visual cortex pre-trained on ImageNet with two datasets of affective images. Our results show that (1) in all layers of the CNN models, there were artificial neurons that responded consistently and selectively to neutral, pleasant, or unpleasant images and (2) lesioning these neurons by setting their output to 0 or enhancing these neurons by increasing their gain led to decreased or increased emotion recognition performance respectively. These results support the idea that the visual system may have the intrinsic ability to represent the affective significance of visual input and suggest that CNNs offer a fruitful platform for testing neuroscientific theories. Author SummaryThe present study shows that emotion selectivity can emerge in deep neural networks trained to recognize visual objects and the existence of the emotion-selective neurons underlies the ability of the network to recognize the emotional qualities in visual images. Obtained using two affective datasets (IAPS and NAPS) and replicated on two CNNs (VGG-16 and AlexNet), these results support the idea that the visual system may have an intrinsic ability to represent the motivational significance of sensory input and CNNs are a valuable platform for testing neuroscience ideas in a way that is not practical in empirical studies.

neuroscience↗

Abeta*56 is a stable oligomer that correlates with age-related memory loss in Tg2576 mice

Amyloid-{beta} (A{beta}) oligomers consist of fibrillar and non-fibrillar soluble assemblies of the A{beta} peptide. Tg2576 human amyloid precursor protein (APP)-expressing transgenic mice modeling Alzheimers disease produce A{beta}*56, a non-fibrillar A{beta} assembly that has been shown by several groups to relate more closely to memory deficits than plaques. Previous studies did not decipher specific forms of A{beta} present in A{beta}*56. Here, we confirm and extend the biochemical characterization of A{beta}*56. We used anti-A{beta}(1-x), anti-A{beta}(x-40), and A11 anti-oligomer antibodies in conjunction with western blotting, immunoaffinity purification, and size-exclusion chromatography to probe aqueous brain extracts from Tg2576 mice of different ages. We found that A{beta}*56 is a [~]56-kDa, SDS-stable, A11-reactive, non-plaque-related, water-soluble, brain-derived oligomer containing canonical A{beta}(1-40) that correlates with age-related memory loss. The unusual stability of this high molecular-weight oligomer renders it an attractive candidate for studying relationships between molecular structure and effects on brain function.

neuroscience↗

A lymph node-to-tumour PD-L1+macrophage circuit antagonizes dendritic cell immunotherapy

Immune-checkpoint blockers (ICB) provide limited benefit against T cell-depleted tumours, calling for therapeutic innovation. Here, we aimed at designing a new type of dendritic cell (DC) vaccine by unbiased computational integration of multi-omics data from cancer patients. In a first attempt, a DC vaccine designed to present tumor antigens from cancer cells succumbing to immunogenic cancer cell death (ICD) and to elicit high type I interferon (IFN) responses failed to induce the regression of mouse tumors lacking T cell infiltrates. In lymph nodes (LNs), instead of activating CD4+ and CD8+T cells, DCs stimulated immunosuppressive PD-L1+LN-associated macrophages (LAMs) via a type I IFN response. Moreover, DC vaccines of this type stimulated pre-existing, T cell-suppressive, PD-L1+tumour-associated macrophages (TAMs). This created a T cell-suppressive circuit of PD-L1+macrophages, spanning across LNs and tumours. Accordingly, DC vaccines synergised with PD-L1 blockade to deplete PD-L1+macrophages, suppress myeloid inflammation affecting the tumor bed and draining lymph nodes, and de-inhibit effector/stem-like memory T cells, eventually causing tumour regression. The synergistic interaction between the DC vaccine and PD-L1 blockade was lost when DCs were manipulated to lose Ifnar1or Ccr7 or when macrophages were depleted. Interestingly, clinical DC vaccines also potentiated lymphocyte-suppressive PD-L1+TAMs in patients bearing T cell-depleted tumours. Altogether, our results reveal the existence of a novel PD-L1+LAM/TAM-driven immunosuppressive pathway that can be elicited by DC vaccines, yet can be subverted for improving the outcome of immunotherapy.

immunology↗

Design, evaluation and implementation of synthetic isopentyldiol pathways in Escherichia coli

Isopentyldiol (IPDO) is an important raw material in cosmetic industry. So far IPDO is exclusively produced through chemical synthesis. Growing interest in natural personal care products has inspired the quest to develop a bio-based process. We previously reported a biosynthetic route that produces IPDO via extending leucine catabolism (route A), the efficiency of which, however, is not satisfactory. To address this issue, we computational designed a novel non-natural IPDO synthesis pathway (Route B) using RetroPath RL, the state of art tool for bio-retrosynthesis based on Artificial Intelligence methods. We compared this new pathway with route A and another two intuitively designed routes for IPDO biosynthesis from various aspects. Route B, which exhibits the highest thermodynamic driving force, least non-native reaction steps and lowest energy requirements appeared to hold the greatest potential for IPDO production. All three newly designed routes were then implemented in E. coli BL21(DE3) strain. Results show that the computationally designed route B can produce 2.2 mg/L IPDO from glucose, whereas no IPDO production from routes C and D. These results highlight the importance and usefulness of in silico design and comprehensive evaluation of the potential efficiencies of candidate pathways in constructing novel non-natural pathways for the production of biochemicals.

bioengineering↗