Expansion and improvement of ChinaMu by MuT-seq and chromosome-level assembly of the Mu-starter genome.

ChinaMu is the largest sequence-indexed Mutator (Mu) transposon insertional library in maize (Zea mays). In this study, we made significant improvements to the size and quality of the ChinaMu library. We developed a new Mu-tag isolation method Mu-Tn5-seq (MuT-seq). Compared to the previous method used by ChinaMu, MuT-seq recovered 1/3 more germinal insertions, while requiring only about 1/14 of the sequencing volume and 1/5 of the experimental time. Using MuT-seq, we identified 113,879 germinal insertions from 3,168 Mu-active F1 families. We also assembled a high-quality genome for the Mu-active line Mu-starter, which harbors the initial active MuDR element and was used as the pollen donor for the mutation population. Using the Mu-starter genome, we recovered 33,662 (15.6%) additional germinal insertions in 3,244 (7.4%) genes in the Mu-starter line. The Mu-starter genome also improved the assignment of 117,689 (54.5%) germinal insertions. The newly upgraded ChinaMu dataset currently contains 215,889 high-quality germinal insertions. These insertions cover 32,224 pan-genes in the Mu-starter and B73Ref5 genomes, including 23,006 (80.4%) core genes shared by the two genomes. As a test model, we investigated Mu insertions in the pentatricopeptide repeat (PPR) superfamily, discovering insertions for 92% (449/487) of PPR genes in ChinaMu, demonstrating the usefulness of ChinaMu as a functional genomics resource for maize.

Technical considerations for cost-effective transposon directed insertion-site sequencing (TraDIS).

Transposon directed insertion-site sequencing (TraDIS), a variant of transposon insertion sequencing commonly known as Tn-Seq, is a high-throughput assay that defines essential bacterial genes across diverse growth conditions. However, the variability between laboratory environments often requires laborious, time-consuming modifications to its protocol. In this technical study, we aimed to refine the protocol by identifying key parameters that can impact the complexity of mutant libraries. Firstly, we discovered that adjusting electroporation parameters including transposome concentration, transposome assembly conditions, and cell densities can significantly improve the recovery of viable mutants for different Escherichia coli strains. Secondly, we found that post-electroporation conditions, such as recovery time and the use of different mediums for selecting mutants may also impact the complexity of viable mutants in the library. Finally, we developed a simplified sequencing library preparation workflow based on a Nextera-TruSeq hybrid design where ~ 80% of sequenced reads correspond to transposon-DNA junctions. The technical improvements presented in our study aim to streamline TraDIS protocols, making this powerful technique more accessible for a wider scientific audience.

EGFR and ERBB2 Exon 20 Insertion Mutations in Chinese Non-small Cell Lung Cancer Patients: Pathological and Molecular Characterization, and First-Line Systemic Treatment Evaluation.

BACKGROUND: Data from studies looking at both EGFR and ERBB2 exon 20 insertion mutations (-20ins) in the same cohort of patients with non-small cell lung cancer (NSCLC) are limited. OBJECTIVE: The purpose of this study was to analyze EGFR/ERBB2-20ins in all-stage NSCLC patients to reveal their histological and molecular features, and to retrospectively evaluate the results of first-line real-world systemic treatments in patients with advanced-stage disease. PATIENTS AND METHODS: We collected 13,920 formalin-fixed paraffin-embedded NSCLC specimens. Clinicopathological features were recorded and DNA-based next-generation sequencing was performed. First-line systemic treatment data were obtained via chart review. RESULTS: In total, 414 (2.97%) EGFR-20ins cases and 666 (4.78%) ERBB2-20ins cases were identified. Both were more common in women, non-smokers, and patients with adenocarcinoma. The incidence of EGFR/ERBB2-20ins in adenocarcinoma is inversely proportional to the degree of invasion; 77 and 26 variants were detected in EGFR-20ins and ERBB2-20ins cases, respectively. The most common concurrently mutated genes were TP53 and RB1. In invasive adenocarcinoma, lepidic components were more common in EGFR/ERBB2-20ins-alone cases than in those with other concurrent mutated genes. In EGFR-/ERBB2-20ins patients, there was no significant difference in progression-free survival (PFS) or treatment response to first-line systemic treatments in this study. There was no significant difference in PFS or treatment response among patients with different EGFR/ERBB2-20ins variants and those with or without concurrent mutated genes. CONCLUSIONS: EGFR/ERBB2-20ins is more common in early lung adenocarcinoma. EGFR-20ins had more variants. In both cohorts, the results for first-line systemic treatments showed no significant difference.

Changing fitness effects of mutations through long-term bacterial evolution.

The distribution of fitness effects of new mutations shapes evolution, but it is challenging to observe how it changes as organisms adapt. Using Escherichia coli lineages spanning 50,000 generations of evolution, we quantify the fitness effects of insertion mutations in every gene. Macroscopically, the fraction of deleterious mutations changed little over time whereas the beneficial tail declined sharply, approaching an exponential distribution. Microscopically, changes in individual gene essentiality and deleterious effects often occurred in parallel; altered essentiality is only partly explained by structural variation. The identity and effect sizes of beneficial mutations changed rapidly over time, but many targets of selection remained predictable because of the importance of loss-of-function mutations. Taken together, these results reveal the dynamic-but statistically predictable-nature of mutational fitness effects.

Advances in the Diagnosis and Treatment of Advanced Non-Small-Cell Lung Cancer With EGFR Exon 20 Insertion Mutation.

The discovery of epidermal growth factor receptor (EGFR) mutations has greatly changed the clinical outlook for patients with advanced non-small-cell lung cancer (NSCLC). Unlike the most common EGFR mutations, such as exon 19 deletion (del19) and exon 21 L858R point mutation, EGFR exon 20 insertion mutation (EGFR ex20ins) is a rare mutation of EGFR. Due to its structural specificity, it exhibits primary resistance to traditional epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), leading to poor overall survival prognosis for patients. In recent years, there has been continuous progress in the development of new drugs targeting EGFR ex20ins, bringing new hope for the treatment of this patient population. In this regard, we conducted a systematic review of the molecular characteristics, diagnostic advances, and treatment status of EGFR ex20ins. We summarized the latest data on relevant drug development and clinical research, aiming to provide reference for clinical diagnosis, treatment, and drug development.

Impact of ACE I gene insertion/deletion, A-240T polymorphisms and the renin-angiotensin-aldosterone system on COVID-19 disease.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic is driven by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which has led to an enormous burden on patient morbidity and mortality. The renin-angiotensin-aldosterone system (RAAS) plays a significant role in various pulmonary diseases. Since SARS-CoV-2 utilizes the angiotensin-converting enzyme (ACE)2 receptor to exert its virulence and pathogenicity, the RAAS is of particular importance in COVID 19. METHODS: Our preliminary study investigates retrospectively the influence of selected ACE-polymorphisms (I/D location at intron 16 in the B-coding sequence (rs4646994) and A-240T (rs 4291) at the A-promoter) as well as ACE1 and ACE2 serum levels on disease severity and the inflammatory response in inpatients and outpatients with COVID-19. RESULTS: Our study included 96 outpatients and 88 inpatients (65.9% male, mean age 60 years) with COVID-19 from April to December 2020 in four locations in Germany. Of the hospitalized patients, 88.6% participants were moderately ill (n = 78, 64% male, median age 60 years), and 11.4% participants were severely ill or deceased (n = 10, 90% male, median age 71 years). We found no polymorphism-related difference in disease, in age distribution, time to hospitalization and time of hospitalization for the inpatient group. ACE1 serum levels were significantly increased in the DD compared to the II polymorphism and in the TT compared to the AA polymorphism. There was no significant difference in ACE 1 serum levels l between moderately ill and severely ill patients. However, participants requiring oxygen supplementation had significantly elevated ACE1 levels compared to participants not requiring oxygen, with no difference in ACE2 levels whereas females had significantly higher ACE2 levels. CONCLUSIONS: Although there were no differences in the distribution of ACE polymorphisms in disease severity, we found increased proinflammatory regulation of the RAAS in patients with oxygen demand and increased serum ACE2 levels in women, indicating a possible enhanced anti-inflammatory immune response. CLINICAL TRIAL REGISTRATION:  PreBiSeCov: German Clinical Trials Register, DRKS-ID: DRKS00021591, Registered on 27th April 2020.

DNA on the move: mechanisms, functions and applications of transposable elements.

Transposons are mobile genetic elements that have invaded all domains of life by moving between and within their host genomes. Due to their mobility (or transposition), transposons facilitate horizontal gene transfer in bacteria and foster the evolution of new molecular functions in prokaryotes and eukaryotes. As transposition can lead to detrimental genomic rearrangements, organisms have evolved a multitude of molecular strategies to control transposons, including genome defense mechanisms provided by CRISPR-Cas systems. Apart from their biological impacts on genomes, DNA transposons have been leveraged as efficient gene insertion vectors in basic research, transgenesis and gene therapy. However, the close to random insertion profile of transposon-based tools limits their programmability and safety. Despite recent advances brought by the development of CRISPR-associated genome editing nucleases, a strategy for efficient insertion of large, multi-kilobase transgenes at user-defined genomic sites is currently challenging. The discovery and experimental characterization of bacterial CRISPR-associated transposons (CASTs) led to the attractive hypothesis that these systems could be repurposed as programmable, site-specific gene integration technologies. Here, we provide a broad overview of the molecular mechanisms underpinning DNA transposition and of its biological and technological impact. The second focus of the article is to describe recent mechanistic and functional analyses of CAST transposition. Finally, current challenges and desired future advances of CAST-based genome engineering applications are briefly discussed.

An efficient targeted gene deletion approach for Cochliobolus heterostrophus using Agrobacterium tumefaciens-mediated transformation.

Cochliobolus heterostrophus is a plant pathogenic fungus of southern corn leaf blight, which has been regarded as a model necrotrophic plant pathogen. Many methods have been developed to knock out targeted genes in C. heterostrophus, of which the most widely-used one is protoplast-mediated transformation. However, there are several problems of this method associated with protoplast preparation, DNA product, time consumption, or high cost. In this study, a highly efficient target gene deletion approach in C. heterostrophus was established and optimized, based on Agrobacterium tumefaciens-mediated transformation (ATMT); the transformation efficiency of this approach was 85-88 transformants per 105 conidia, and the homologous recombination efficiency was approximately 68.3%. Furthermore, six gene knockout mutants of C. heterostrophus were obtained using this ATMT method. The phenotypes of this fungus altered in the mutant strains, and the virulence of the mutants significantly reduced compared to of the wild type strain. Taken together, this ATMT system established in this study can be used as a genetic manipulation tool for C. heterostrophus, to better understand the functions of genes and its relation to virulence.

Trastuzumab deruxtecan (DS8201) for advanced non-small cell lung cancer with HER2 exon 20 insertion mutation: a case report.

An antibody-drug conjugate (ADC) of human epidermal growth factor receptor-2 (HER2) provides effective treatment for patients with HER2-positive non-small cell lung cancer (NSCLC). Exon 20 insertion mutations are the most common among HER2 mutations. This mutant subtype is highly drug-resistant, and patients receiving conventional treatment often have a poor prognosis. Trastuzumab deruxtecan (T-DXd), a novel anti-HER2 ADC, has emerged as a novel treatment option for HER2-positive (mutated, expressed, amplified, alternated) NSCLC, based on several studies and reported results. Herein, we report a case of stage IV NSCLC with HER2 exon 20 mutation in a 52-year-old male patient whose tumor recurred after radical resection of pulmonary carcinoma, who could not tolerate chemotherapy, and presented with bone metastasis. After treatment with T-DXd, the tumor significantly regressed and bone metastasis improved, maintaining a state of no progression for 21 months. This case report evidences the use of T-DXd in the treatment of NSCLC with HER2 exon 20 insertion mutation.

Deletions within intronic T-DNA lead to reversion of T-DNA mutant phenotypes.

Agrobacterium-mediated transformation enables random transfer-DNA (T-DNA) insertion into plant genomes. T-DNA insertion into a gene's exons, introns or untranscribed regions close to the start or stop codon can disrupt gene function. Such T-DNA mutants have been useful for reverse genetics analysis, especially in Arabidopsis thaliana. As T-DNAs are inserted into genomic DNA, they are generally believed to be stably inherited. Here, we report a phenomenon of reversion of intronic T-DNA mutant phenotypes. From a suppressor screen using intronic T-DNA pi4kß1,2 double mutant, we recovered intragenic mutants of pi4kß1, which suppressed the autoimmunity of the double mutant. These mutants carried deletions in the intronic T-DNAs, resulting in elevated transcription of normal PI4Kß1. Such reversion of T-DNA insertional mutant phenotype stresses the need for caution when using intronic T-DNA mutants and reiterates the importance of using irreversible null mutant alleles in genetic analyses.

Safety, Tolerability, Pharmacokinetics, and Preliminary Efficacy of YK-029A in Treatment-Naive Patients With Advanced NSCLC Harboring EGFR Exon 20 Insertion Mutations: A Phase 1 Trial.

INTRODUCTION: Treatment options for treatment-naive patients with advanced NSCLC harboring EGFR exon 20 insertion (ex20ins) mutations are limited. This study evaluated the safety, tolerability, and pharmacokinetics of YK-029A, a third-generation EGFR tyrosine kinase inhibitor, and the preliminary efficacy of YK-029A in treatment-naive patients with EGFR ex20ins mutation. METHODS: This multicenter, dose-escalation, and dose-expansion phase 1 clinical trial enrolled patients with NSCLC harboring EGFR mutations. During the dose-escalation phase, YK-029A was orally administered using the traditional 3+3 principle at 50, 100, 150, 200, and 250 mg/d. In the dose-expansion phase, treatment-naive patients with EGFR ex20ins mutations were enrolled and administered YK-029A 200 mg/d. The primary end point was safety and tolerability. RESULTS: The safety analysis included 108 patients. No dose-limiting toxicity was observed, and the maximum tolerated dose was not reached. The most common treatment-emergent adverse events were anemia (50.9%), diarrhea (49.1%), and rash (34.3%). There was minimal drug accumulation after multiple doses. A total of 28 treatment-naive patients with EGFR ex20ins mutations were enrolled in the dose-expansion and 26 were included in the efficacy analysis. According to the independent review committee evaluation, the objective response rate was 73.1% (95% confidence interval: 52.21%-88.43%), and the disease control rate was 92.3% (95% confidence interval: 74.87%-99.05%). CONCLUSIONS: YK-029A was found to have manageable safety and be tolerable in patients with NSCLC harboring EGFR mutations and have promising antitumor activity in untreated patients with EGFR ex20ins mutations.

Randomly barcoded transposon mutant libraries for gut commensals I: Strategies for efficient library construction.

Randomly barcoded transposon mutant libraries are powerful tools for studying gene function and organization, assessing gene essentiality and pathways, discovering potential therapeutic targets, and understanding the physiology of gut bacteria and their interactions with the host. However, construction of high-quality libraries with uniform representation can be challenging. In this review, we survey various strategies for barcoded library construction, including transposition systems, methods of transposon delivery, optimal library size, and transconjugant selection schemes. We discuss the advantages and limitations of each approach, as well as factors to consider when selecting a strategy. In addition, we highlight experimental and computational advances in arraying condensed libraries from mutant pools. We focus on examples of successful library construction in gut bacteria and their application to gene function studies and drug discovery. Given the need for understanding gene function and organization in gut bacteria, we provide a comprehensive guide for researchers to construct randomly barcoded transposon mutant libraries.

Randomly barcoded transposon mutant libraries for gut commensals II: Applying libraries for functional genetics.

The critical role of the intestinal microbiota in human health and disease is well recognized. Nevertheless, there are still large gaps in our understanding of the functions and mechanisms encoded in the genomes of most members of the gut microbiota. Genome-scale libraries of transposon mutants are a powerful tool to help us address this gap. Recent advances in barcoded transposon mutagenesis have dramatically lowered the cost of mutant fitness determination in hundreds of in vitro and in vivo experimental conditions. In an accompanying review, we discuss recent advances and caveats for the construction of pooled and arrayed barcoded transposon mutant libraries in human gut commensals. In this review, we discuss how these libraries can be used across a wide range of applications, the technical aspects involved, and expectations for such screens.

Sunvozertinib for patients in China with platinum-pretreated locally advanced or metastatic non-small-cell lung cancer and EGFR exon 20 insertion mutation (WU-KONG6): single-arm, open-label, multicentre, phase 2 trial.

BACKGROUND: Sunvozertinib is an oral, irreversible, and selective tyrosine kinase inhibitor that has a favourable safety profile and encouraging antitumour activity, as shown in phase 1 studies of patients with heavily pretreated non-small cell lung cancer (NSCLC) with EGFR exon 20 insertion mutation (exon20ins). We aimed to assess the antitumour efficacy of sunvozertinib in patients with platinum-pretreated locally advanced or metastatic NSCLC with EGFR exon20ins. METHODS: WU-KONG6 is a single-group, open-label, multicentre phase 2 trial of sunvozertinib monotherapy, conducted across 37 medical centres in China. We enrolled adult patients with pathologically or cytologically confirmed locally advanced or metastatic NSCLC whose tumour tissue carried an EGFR exon20ins mutation. All patients had received at least one line of previous systemic therapy, with at least one line containing platinum-based chemotherapy. The primary endpoint was objective response rate (ORR), as assessed by the independent review committee. The ORR was defined as the percentage of patients who achieved complete or partial response, confirmed by two separate assessments with at least 4-week time interval, until disease progression or initiation of any new anti-cancer therapy. Enrolled patients received sunvozertinib 300 mg once daily until meeting discontinuation criteria per the protocol. Patients who received at least one dose of treatment and were evaluable for efficacy analysis were included in the primary analysis, and all patients who received at least one dose of treatment were included in the safety analysis. This study is registered with ChinaDrugTrials.org, CTR20211009, and ClinicalTrials.gov, NCT05712902, and efficacy and safety follow-up are ongoing. FINDINGS: Between July 19, 2021, and May 6, 2022, 104 patients were enrolled. At data cutoff (Oct 17, 2022), the last enrolled patient had been followed up for about 6 months. Among 97 patients evaluable for efficacy analysis, 59 (61%) patients achieved tumour response, with a confirmed ORR of 61% (95% CI 50-71). All tumour responses were partial responses. Tumour responses were observed irrespective of age, sex, smoking history, EGFR exon20ins subtypes, brain metastasis at baseline, previous lines of therapy, and history of onco-immunotherapy. In total, 19 death events occurred over a median follow-up period of 7·6 months (IQR 6·1-9·4). Sunvozertinib was well tolerated at 300 mg once daily. The most common grade 3 or worse treatment-related adverse events were blood creatine phosphokinase increased (18 [17%] of 104), diarrhoea (eight [8%]), and anaemia (six [6%]). The most common serious treatment-related adverse events were interstitial lung disease (five [5%] of 104), anaemia (three [3%]), vomiting (two [2%]), nausea (two [2%]) and pneumonia (two [2%]). INTERPRETATION: In this phase 2 study, sunvozertinib demonstrated antitumour efficacy in patients with platinum-based chemotherapy pretreated NSCLC with EGFR exon20ins, with a manageable safety profile. A multinational randomised, phase 3 study of sunvozertinib versus platinum-doublet chemotherapy in EGFR exon20ins NSCLC is ongoing (NCT05668988). FUNDING: Dizal Pharmaceutical.

The evaluation of superoxide dismutase 1 gene insertion/deletion variant in athletes.

OBJECTIVE: Regular exercise benefits health by increasing the body's antioxidant defenses. However, excessive exercise can produce excessive reactive oxygen species, which can lead to oxidative stress. Superoxide dismutase is the primary enzyme involved in the elimination of reactive oxygen species. This study aimed to determine the relationship between the SOD1 gene insertion/deletion variant and elite athletes. METHODS: A total of 305 subjects, including 165 elite athletes from different branches and 140 sedentary individuals, participated in this study. The SOD1 insertion/deletion variant was genotyped using polymerase chain reaction. The results were evaluated statistically. RESULTS: There was no statistical significance between the athletes and control groups in terms of SOD1 insertion/deletion genotype distribution and allele frequency. Then, we evaluated the groups as females and males. There were no female athletes carrying the D/D genotype. The SOD1 I/I genotype and the I allele were more prevalent in female athletes than in the control group. There was a significant difference in terms of SOD1 I/I: I/D+D/D in females (p=0.028). SOD1 genotype and allele distribution did not differ between male athletes and male controls. CONCLUSION: As far as we know, this is the first study to evaluate the SOD1 insertion/deletion variant in athletes in Turkey. Our results showed that the SOD1 I allele was more common in female athletes, but not in male athletes.

Expression and high levels of insertional polymorphism of an endogenous gammaretrovirus lineage in dogs.

Despite the absence of a confirmed exogenously replicating retrovirus in Canis lupus familiaris (C. familiaris), past retroviral infections are evident in the genomes of living animals via the presence of endogenous retroviruses (ERVs). Although gammaretrovirus-like transcripts and enzyme activities were previously reported to be present in canine leukemias and lymphomas, those findings were not further explored. Initial analysis of the C. familiaris reference genome revealed a minor subset of one ERV lineage, classified as CfERV-Fc1(a), or Fc1(a) here, with features characteristic of recent integration, including the presence of ORFs and identical or nearly identical LTRs. Our previous analysis of whole genome sequence data belonging to extant Canidae revealed a burst of past infections in Canis ancestors resulting in numerous young, polymorphic, and highly intact loci now segregating in dogs. Here, we demonstrate the expression of full-length Fc1(a) proviruses in tissues collected from healthy animals and from animals with cancer. We observed significantly higher expression in samples of dogs with various cancer diagnoses when compared to samples from healthy dogs. Genotyping of insertionally polymorphic Fc1(a) loci identified candidate expressed proviruses and delineated distributions over sample groups. Collectively, the data show that Fc1(a) proviruses retain biological activity in the domestic dog and provides a means to examine potential genetic links with disease states in this species.

Microbial Primer: Transposon directed insertion site sequencing (TraDIS): A high throughput method for linking genotype to phenotype.

Genetic screens are a key tool for linking phenotype and genotype. Transposon mutagenesis was one of the first genetic methodologies to associate genetic loci with phenotypes. The advent of next-generation sequencing transformed the use of this technique allowing rapid interrogation of whole genomes for genes that correlate with phenotype. One method is transposon directed insertion-site sequencing (TraDIS). Here we describe the method, recent developments in technology, and the advantages and disadvantages of this method compared to other genetic screening tools.

Evidence for widespread existence of functional novel and non-canonical human transcripts.

BACKGROUND: Fraction of functional sequence in the human genome remains a key unresolved question in Biology and the subject of vigorous debate. While a plethora of studies have connected a significant fraction of human DNA to various biochemical processes, the classical definition of function requires evidence of effects on cellular or organismal fitness that such studies do not provide. Although multiple high-throughput reverse genetics screens have been developed to address this issue, they are limited to annotated genomic elements and suffer from non-specific effects, arguing for a strong need to develop additional functional genomics approaches. RESULTS: In this work, we established a high-throughput lentivirus-based insertional mutagenesis strategy as a forward genetics screen tool in aneuploid cells. Application of this approach to human cell lines in multiple phenotypic screens suggested the presence of many yet uncharacterized functional elements in the human genome, represented at least in part by novel exons of known and novel genes. The novel transcripts containing these exons can be massively, up to thousands-fold, induced by specific stresses, and at least some can represent bi-cistronic protein-coding mRNAs. CONCLUSIONS: Altogether, these results argue that many unannotated and non-canonical human transcripts, including those that appear as aberrant splice products, have biological relevance under specific biological conditions.