Subject: Life Sciences, Biochemistry Keywords: ganglioside; knockout; neurodegeneration; glycosphingolipid; inflammation; microdomain
Online: 3 February 2020 (06:00:23 CET)
Acidic glycosphingolipids, gangliosides are highly and consistently expressed in nervous tissues of vertebrates at high levels. Therefore, they have been believed to be largely involved in the development and function of nervous systems. Recent studies with genetic engineering of glycosyltransferase genes have revealed novel aspects of roles of gangliosides in the regulation of nervous tissues with substantial basis. In this review, novel findings on the ganglioside functions and their modes of action elucidated mainly by studies of gene knockout mice have been summarized. In particular, roles of gangliosides in the regulation of lipid rafts to maintain the integrity of nervous systems have been reported with a focus on the roles in the regulation of neuro-inflammation and neurodegeneration via complement systems. In addition, recent advances in the studies of congenital neurodisorders due to the genetic mutaions of ganglioside synthase genes, and also in the techniques for the analysis of ganglioside functions have been introduced.
COMMUNICATION | doi:10.20944/preprints202005.0253.v1
Subject: Life Sciences, Genetics Keywords: Cas9; Cas12a; Cpf1; zebrafish; gene knockout; repair outcome
Online: 15 May 2020 (10:16:55 CEST)
CRISPR/Cas genome editing is a widely used research technology. Its simplest variant is gene knockout resulting from reparation errors after introduction of dsDNA breaks by Cas nuclease. We compared the outcomes of the break repair by two commonly used nucleases (SpCas9 and LbCas12a) in zebrafish embryos to reveal if application of one nuclease is advantageous in comparison to the other. To address this question, we injected ribonucleoprotein complexes of nucleases and corresponding guide RNAs in zebrafish zygotes and three days later sequenced the target gene regions. We found that LbCas12a breaks resulted in longer deletions and more rare inserts, in comparison to those generated by SpCas9, while the editing efficiencies of both nucleases were the same. On the other hand, overlapping protospacers were shown to lead to similarities in repair outcome, although they were cut by two different nucleases. Thus, our results indicate that the repair outcome depends both on the nuclease mode of action and on protospacer sequence.
ARTICLE | doi:10.20944/preprints202106.0357.v1
Subject: Life Sciences, Biochemistry Keywords: CYP1B1; craniofacial development; CRISPR/Cas9; Congenital glaucoma; knockout zebrafish.
Online: 14 June 2021 (11:53:54 CEST)
CYP1B1 loss-of-function (LoF) is the main known genetic alteration present in recessive primary congenital glaucoma (PCG), an infrequent disease characterized by delayed embryonic development of the ocular iridocorneal angle and caused by poorly understood molecular mechanisms. To model CYP1B1 LoF underlying PCG, we developed a cyp1b1 knockout (KO) zebrafish line using CRISPR/Cas9 genome editing. This line carries the c.535_667del frameshift mutation that results in a 72% mRNA reduction with residual mRNA predicted to produce an inactive truncated protein (p.(His179Glyfs*6)). Craniofacial defects and jaw maldevelopment were observed in 23% of somatic mosaic F0 crispant larvae (144 hpf). These early phenotypes were not detected in KO F3 larvae (144 hpf) but 27% of adult fishes (4 months) showed uni or bilateral craniofacial alterations, indicating the existence of incomplete penetrance and variable expressivity. These phenotypes increased to 86% in the adult offspring of inbred progenitors with craniofacial defects. No glaucoma-related phenotypes were observed in the cyp1b1 mutants. Transcriptomic analyses of the offspring (7dpf) of KO cyp1b1 progenitors with adult-onset craniofacial defects revealed that differentially expressed genes were functionally enriched in groups related with extracellular matrix and cell adhesion, cell growth and proliferation, lipid metabolism (retinoids, steroids, and fatty acids, and oxidation-reduction processes which included several cytochrome P450 genes) and inflammation. In summary, this study shows the complexity of phenotypes and molecular pathways associated with cyp1b1 LoF, with species-dependency, and provides evidence for dysregulation of extracellular matrix gene expression as one of the mechanisms underlaying pathogenicity associated with cyp1b1 disruption.
ARTICLE | doi:10.20944/preprints202010.0484.v1
Subject: Biology, Anatomy & Morphology Keywords: inorganic polyphosphate; VTC4; knockout mutant; oxidative stress; gene expression; yeast
Online: 23 October 2020 (10:42:43 CEST)
Inorganic polyphosphate (polyP) is an important factor of stress tolerance in microbial cells. In yeast, the major enzyme of polyP biosynthesis is Vtc4, a subunit of the vacuole transporter chaperone (VTC) complex. In this study, we demonstrated that Vtc4 knockout in Saccharomyces cerevisiae not only decreased polyP content but also caused shifts in the composition of the intracellular polyP pool and changed the stress tolerance profile. In the mutant S. cerevisiae, the level of short-chain acid-soluble polyPs was decreased nearly 10-fold, whereas that of longer acid-insoluble polyPs was decreased only 2-fold, suggesting the existence of other enzymes compensating the production of long-chain polyPs. The Δvtc4 mutant showed inhibition of Mg2+-dependent phosphate uptake and decreased resistance to alkaline stress but increased tolerance to oxidation and heavy metal ions, especially Mn2+. Quantitative PCR revealed the upregulation of the DDR2 gene implicated in multiple stress responses and downregulation of PHO84 encoding a phosphate and Mn2+ transporter, which could account for the effects on phosphate uptake and Mn2+-related stress response in the Δvtc4 mutant. Our study indicates that short-chain polyPs, plays an important role in the regulation of stress response in yeast.
ARTICLE | doi:10.20944/preprints202208.0159.v1
Subject: Life Sciences, Endocrinology & Metabolomics Keywords: metabolomics; NMR; PEMT; knockout; aging; mice; liver; intestine; white/brown adipose tissue
Online: 8 August 2022 (13:36:04 CEST)
Phospholipid metabolism, including phosphatidylcholine (PC) biosynthesis, is crucial for various biological functions and is associated to longevity. Phosphatidylethanolamine N-methyltransferase (PEMT) is a protein that catalyzes the biosynthesis of PC, the levels of which change in various organs such as brain and kidney during aging. However, the role of PEMT for systemic PC supply is not fully understood. To address how PEMT affects aging-associated energy metabolism in tissues responsible for nutrient absorption, lipid storage and energy consumption, we employed NMR-based metabolomics to study liver, plasma, intestine (duodenum, jejunum, ileum), brown/white adipose tissues (BAT, WAT), and skeletal muscle of young (9–10 weeks) and old (96–104 weeks) wild-type (WT) and PEMT knockout (KO) mice. We found that the effect of PEMT-knockout was tissue-specific and age-dependent. Deficiency of PEMT affected the metabolome of all tissues examined, among which the metabolome of BAT from both young and aged KO mice was dramatically changed in comparison to WT mice, whereas the metabolome of jejunum was only slightly affected. As for aging, the absence of PEMT increased the divergence of metabolome during aging of liver, WAT, duodenum and ileum and decreased the impact on skeletal muscle. Overall, our results suggest that PEMT plays a previously unexplored critical role in both aging and energy metabolism.
ARTICLE | doi:10.20944/preprints202111.0013.v1
Subject: Life Sciences, Molecular Biology Keywords: Nonsense-mediated mRNA Decay; UPF3B-knockout; RNA-Sequencing; Intellectual disability; Neuro-developmental disorders
Online: 1 November 2021 (12:17:15 CET)
UPF3B is a constituent of the classical nonsense-mediated mRNA decay (NMD) pathway that degrades both the aberrant transcripts and a set of physiological transcripts. In higher eukaryotes, UPF3B have significant biochemical functions in diverse cellular processes including NMD and translation. UPF3B plays a crucial role in neuronal development and differentiation. Next-generation sequencing technologies identified several loss-of-function mutations in the UPF3B gene that results in neuro-developmental disorders in humans. To uncover the mechanistic role of UPF3B in neuronal functions, we have generated the UPF3B-knockout mammalian cell line model system using CRISPR-Cas9 gene editing method. RNA-Sequencing Analysis of cellular transcriptome from UPF3B-KO cells identified specific genes involved in cell growth and neuronal functions. Altered expression of genes related to the axon guidance pathway delineated the UPF3B function to regulate the neuron-specific genes. Functional enrichment analysis identified the genes involved in the disorders related to mental health and intellectual disability. Our study has the potential to identify the direct players of intellectual disability and will have broader implications.
ARTICLE | doi:10.20944/preprints202109.0051.v1
Subject: Biology, Entomology Keywords: Helicoverpa zea; Bollworm; CRISPR; Cry1A; Bt Toxin; Genome Editing; Knockout; Functional Genomics; Resistance
Online: 3 September 2021 (08:19:44 CEST)
Members of the insect ATP binding cassette transporter subfamily C2 (ABCC2) in several moth species are known as receptors for the Cry1Ac insecticidal protein from Bacillus thuringiensis (Bt). Mutations that abolish the functional domains of ABCC2 are known to cause resistance to Cry1Ac, although the reported levels of resistance vary widely depending on insect species. In this study, the function of the ABCC2 gene as putative Cry1Ac receptor in Helicoverpa zea, a major pest of over 300 crops, was evaluated using CRISPR/Cas9 to progressively eliminate different functional ABCC2 domains. Results from bioassays with edited insect lines support that muta-tions in ABCC2 was associated with Cry1Ac resistance ratios (RR) ranging from 7.3- to 39.8-fold. No significant differences in susceptibility to Cry1Ac were detected between H. zea with partial or complete ABCC2 knockout, although highest levels of tolerance were observed when knocking out half of ABCC2. Based on >500-1,000-fold RRs reported in similar studies for closely related moth species, the low RRs observed in H. zea knockouts support that ABCC2 is not a major Cry1Ac receptor in this insect.
ARTICLE | doi:10.20944/preprints202104.0474.v1
Subject: Life Sciences, Biochemistry Keywords: CRISPR/Cas9; knockout; rescue; desiccation tolerance; anhydrobiosis; Polypedilum vanderplanki; HSF1; insect cell; Pv11
Online: 19 April 2021 (12:17:34 CEST)
Pv11, an insect cell line established from the midge Polypedilum vanderplanki, is capable of ametabolic desiccation tolerance, so-called anhydrobiosis. We previously discovered that heat shock factor 1 (HSF1) contributes to the acquisition of desiccation tolerance by Pv11 cells, but the mechanistic details have yet to be elucidated. Here, by analyzing the gene expression profiles of newly established HSF1-knockout and -rescue cell lines, we show that HSF1 has a genome-wide effect on gene regulation in Pv11. HSF1-knockout cells exhibit a reduced desiccation survival rate, but this is completely restored in HSF1-rescue cells. By comparing mRNA profiles of the two cell lines, we reveal that HSF1 induces anhydrobiosis-related genes, especially genes encoding late embryogenesis abundant proteins and thioredoxins, but represses a group of genes involved in basal cellular processes, thus promoting an ametabolic state in the cell. In addition, HSF1 binding motifs are enriched in the promoters of anhydrobiosis-related genes and we demonstrate binding of HSF1 to these promoters by ChIP-qPCR. Thus, HSF1 directly regulates the transcription of anhydrobiosis-related genes and consequently plays a pivotal role in the induction of anhydrobiotic ability in Pv11 cells.
ARTICLE | doi:10.20944/preprints201903.0163.v1
Subject: Biology, Ecology Keywords: Ranavirus; FV3; vIF-2α knockout mutant; bath exposure; wood frog; sublethal effects; reservoir host
Online: 15 March 2019 (11:58:03 CET)
Ranaviruses have been associated with rising numbers of mass die-offs in amphibian populations globally. With life-stages occupying different environments and presenting distinct physiologies, amphibian of different ages are likely to play an important role in pathogen persistence. To assess the potential role of post-metamorphic amphibians as a Ranavirus reservoir, we performed a bath-exposure study on wood frogs using environmentally relevant doses (~103 and ~104 PFU/mL) of wild-type (WT) and knockout Frog virus 3 (FV3), deficient for the vIF-2α immune-evasion gene, the effects of which have never been addressed in post-metamorphic anurans. We observed 42% infection prevalence and low mortality (10%) across the virus challenges, with half of the mortalities attributable to ranavirosis. Prevalence and viral loads followed a dose-dependent pattern. Notably, when exposed to the vIF-2α knockout (DvIF-2α) FV3, individuals exhibited significantly decreased growth and increased lethargy in comparison to WT FV3 treatments. Although 85% of individuals in the virus treatments exhibited stereotypic signs of ranavirosis throughout the experiment, at termination (40 days post exposure) most individuals were clear of signs of infection. Overall, this study provides evidence that even a single short time exposure to environmentally relevant doses of Ranavirus may cause sublethal infections in post-metamorphic amphibians, thus indicating their possible role as a reservoir for this pathogen.
ARTICLE | doi:10.3390/sci2020043
Subject: Keywords: lactate dehydrogenase; alanine transaminase; MDR2 knockout; dissolution dynamic nuclear polarization; perfused precision cut liver slices
Online: 10 June 2020 (00:00:00 CEST)
The clinical characterization of small hepatocellular carcinoma (HCC) lesions in the liver and differentiation from heterogeneous inflammatory or fibrotic background is important for early detection and treatment. Metabolic monitoring of hyperpolarized 13C-labeled substrates has been suggested as a new avenue for diagnostic magnetic resonance. The metabolism of hyperpolarized [1-13C]pyruvate was monitored in mouse precision-cut liver slices (PCLS) of aged MDR2-KO mice, which served as a model for heterogeneous liver and HCC that develops similarly to the human disease. The relative in-cell activities of lactate dehydrogenase (LDH) to alanine transaminase (ALT) were found to be 0.40 ± 0.06 (n = 3) in healthy livers (from healthy mice), 0.90 ± 0.27 (n = 3) in heterogeneously inflamed liver, and 1.84 ± 0.46 (n = 3) in HCC. Thus, the in-cell LDH/ALT activities ratio was found to correlate with the progression of the disease. The results suggest that the LDH/ALT activities ratio may be useful in the assessment of liver disease. Because the technology used here is translational to both small liver samples that may be obtained from image-guided biopsy (i.e., ex vivo investigation) and to the intact liver (i.e., in a non-invasive MRI scan), these results may provide a path for differentiating heterogeneous liver from HCC in human subjects.
REVIEW | doi:10.20944/preprints202208.0444.v1
Subject: Medicine & Pharmacology, Oncology & Oncogenics Keywords: prostate cancer; knockout mouse models; genetically-engineered mouse models; xenografts; patient derived xenografts; organoids; signaling pathways
Online: 26 August 2022 (04:16:25 CEST)
In 2022, prostate cancer (PCa) is estimated to be the most commonly diagnosed cancer in men in the United States – almost 270,000 American men are estimated to be diagnosed with PCa in 2022 . This review compares and contrasts in vivo models of PCa with regards to the altered genes, signaling pathways, and stages of tumor progression associated with each model. The main type of model included in this review are genetically engineered mouse models, which include conditional and constitutive knockout model. 2D cell lines, 3D organoids and spheroids, xenografts and allografts, and patient derived models are also included. The major applications, advantages and disadvantages, and ease of use and cost are unique to each type of model, but they all make it easier to translate the tumor progression that is seen in the mouse prostate to the human prostate. Although both human and mouse prostates are androgen-dependent, the fact that the native, genetically unaltered prostate in mice cannot give rise to carcinoma is an especially critical component of PCa models. Thanks to the similarities between the mouse and human genome, our knowledge of PCa has been expanded, and will continue to do so, through models of PCa.
ARTICLE | doi:10.20944/preprints202106.0169.v1
Subject: Life Sciences, Biochemistry Keywords: melanoma initiating cells; CD133; drug resistance; apoptosis; caspase activation; CRISPR-Cas9 knockout; AKT; BAD; BCL-2 family
Online: 7 June 2021 (12:11:10 CEST)
Malignant melanoma is a lethal skin cancer containing melanoma-initiating cells (MIC), implicated in tumorigenesis, invasion, and drug resistance, and characterized by elevated expression of stem cell markers, such as CD133. We previously showed that siRNA knockdown of CD133 enhances apoptosis induced by the MEK inhibitor trametinib in melanoma cells. The current study investigates underlying mechanisms of CD133’s anti-apoptotic activity in patient-derived BAKP and POT cells, harboring difficult-to-treat NRASQ61K and NRASQ61R drivers, after CRISPR-Cas9 CD133 knockdown or Dox-inducible expression of CD133. To maintain stable expression of CD133, MACS-sorted CD133(+) positive cells were expanded by ROCK-mediated conditional reprogramming of BAKP melanoma cells (BAKR). BAKR showed increased survival via reduced apoptosis after exposure to trametinib or DTIC, compared to BAKP. CRISPR-Cas9- mediated CD133 knockdown in BAKR cells (BAKR-T3) re-sensitized the cells, while CRISPR-Cas9 knockdown of CD133 in parental BAKP and POT cells even further increased trametinib-induced apoptosis (cleaved PARP) by reducing levels of anti-apoptotic BCL-xL, p-AKT, and p-BAD, and increasing pro-apoptotic BAD and active BAX. Dox-induced CD133 overexpression had the opposite effect, and blocked trametinib-induced apoptosis in both cell lines, coincident with elevated p-AKT, p-BAD, BCL-2 and BCL-xL and decreased levels of the active form of BAX and caspases-3 and -9. The roles of CD133 in AKT and BAD phosphorylation, or in the upregulation of anti-apoptotic BCL-2 family members, was further investigated by AKT knockout with siRNA, or inhibition of BCL-2 family members with navitoclax (ABT-263). Similar to CD133 knockdown, AKT1/2 siRNA knockdown in BAKP cells also reduced p-BAD. CD133 knockdown (T3)-mediated reduction of pBAD levels was equivalent in AKT-knockdown or AKT control cells indicating that CD133 may be upstream of AKT signaling. In BAKP cells treated with trametinib and/or ABT-263, effects of ABT-263 mirrored CD133 knockdown, since levels of active BAX and cleaved-PARP in BAKP-SC (CD133-) cells increased to the same level as that exhibited by BAKP-T3 cells (CD133+). CD133 may therefore activate a survival pathway where 1) increased phosphorylation of AKT induces 2) phosphorylation and inactivation of BAD, 3) decrease in the active form of BAX, and 4) reduction in caspase-mediated PARP cleavage, indicating apoptosis suppression leading to drug resistance in melanomas. Targeting survival pathways by which CD133 may confer chemoresistance in MICs can contribute to development of more effective treatments for patients with high-risk melanoma.
ARTICLE | doi:10.20944/preprints202012.0398.v1
Subject: Medicine & Pharmacology, Allergology Keywords: 1α,25-dihydroxyvitaminD3; photoprotection; DNA damage; cyclobutane pyrimidine dimers; edema; photoimmune suppression; female vs male mice; ER-β knockout
Online: 16 December 2020 (08:49:22 CET)
Susceptibility to photoimmune suppression and photocarcinogenesis is greater in male than in female humans and mice and is exacerbated in female estrogen receptor-beta knockout (ER-β-/-) mice. We previously reported that the active vitamin D hormone, 1,25-dihydroxyvitamin D3 (1,25(OH)2D) applied topically protects against ultraviolet radiation (UV)-induction of cutaneous cyclobutane pyrimidine dimers (CPDs) and suppression of contact hypersensitivity (CHS) in female mice. Here we compare these responses in female versus male Skh:hr1 mice, in ER-β-/- versus wild type C57BL/6 mice, and in female ER-blockaded Skh:hr1 mice. Induction of CPDs was significantly greater in male than female Skh:hr1 mice and was more effectively reduced by 1,25(OH)2D in female Skh:hr1 and C57BL/6 mice, than in male Skh:hr1 or ER-β-/- mice respectively. This correlated with reduced sunburn inflammation by 1,25(OH)2D in female but not male Skh:hr1 mice. Furthermore, although 1,25(OH)2D alone dose-dependently suppressed basal CHS responses in male Skh:hr1 and ER-β-/- mice, UV-induced immunosuppression was universally observed. In female Skh:hr1 and C57BL/6 mice, the immunosuppression was decreased by 1,25(OH)2D dose-dependently, but not in male Skh:hr1, ER-β-/- or ER-blockaded mice. These results reveal a sex bias in genetic, inflammatory and immune photoprotection by 1,25(OH)2D favoring female mice, that is dependent on the presence of ER-β.
ARTICLE | doi:10.20944/preprints202203.0290.v2
Subject: Life Sciences, Biotechnology Keywords: host-virus interactions; tissue-specific model; COVID-19; SARS-CoV-2; antiviral targets; flux balance analysis; flux variability analysis; reaction knockout; host-derived enforcement; metabolic modeling; virus mutations; nucleoside diphosphate kinase; software engineering; Python
Online: 27 July 2022 (10:37:12 CEST)
COVID-19 has been characterized as one of the deadliest respiratory diseases, and the emergence of SARS-CoV-2 caught the pharmaceutical industry and the drug development communities off guard. Identifying potential antiviral targets is of great concern, and one way to detect them is by analyzing metabolic changes in infected cells. In this study, we present a novel workflow to predict robust druggable targets against emerging RNA viruses using metabolic networks and information of the viral structure and its genome sequence. For this purpose, we implemented pymCADRE, a tool to create metabolic models using gene expression data, and used this to reconstruct a metabolic network of the human bronchial epithelial cells. We observed that pymCADRE reduces the computational time when flux variability analysis is employed for internal optimizations. Subsequently, we created a fully automated computational tool, named PREDICATE, which analyses one or more nucleotide sequences, introduces given amino acid mutations, and simulates in silico viral infections. Moreover, it predicts a set of host reactions, which, when constrained, inhibit the virus production while preserving the host’s optimal state. In the context of SARS-CoV-2, we applied this tool to our metabolic network of bronchial epithelial cells and identified enzymatic reactions with inhibitory effects. From the list of the reported targets, the most promising one was the Nucleoside Diphosphate Kinase, whose inhibitors have already been reported in the literature. Finally, we computationally tested the robustness of our targets in all currently known variants of concern, verifying the inhibitory effect of our target enzyme against SARS-CoV-2. Focusing on the metabolic fluxes of infected cells, we aim at applying our workflow and methods for rapid hypothesis-driven identification of potentially exploitable antivirals to efficiently prevent future pandemics concerning various viruses and host cell types.