Clinical and molecular significance of homologous recombination deficiency positive non-small cell lung cancer in Chinese population:An integrated genomic and transcriptional analysis

Objective:The clinical significance of homologous recombination deficiency(HRD)in breast cancer,ovarian cancer,and prostate cancer has been established,but the value of HRD in non-small cell lung cancer(NSCLC)has not been fully investigated.This study aimed to systematically analyze the HRD status of untreated NSCLC and its relationship with patient prognosis to further guide clinical care.Methods:A total of 355 treatment-naïve NSCLC patients were retrospectively enrolled.HRD status was assessed using the AmoyDx Genomic Scar Score(GSS),with a score of≥50 considered HRD-positive.Genomic,transcriptomic,tumor microenvironmental characteristics and prognosis between HRD-positive and HRDnegative patients were analyzed.Results:Of the patients,25.1%(89/355)were HRD-positive.Compared to HRD-negative patients,HRDpositive patients had more somatic pathogenic homologous recombination repair(HRR)mutations,higher tumor mutation burden(TMB)(P<0.001),and fewer driver gene mutations(P<0.001).Furthermore,HRD-positive NSCLC had more amplifications in PI3K pathway and cell cycle genes,MET and MYC in epidermal growth factor receptor(EGFR)/anaplastic lymphoma kinase(ALK)mutant NSCLC,and more PIK3CA and AURKA in EGFR/ALK wild-type NSCLC.HRD-positive NSCLC displayed higher tumor proliferation and immunosuppression activity.HRD-negative NSCLC showed activated signatures of major histocompatibility complex(MHC)-II,interferon(IFN)-γand effector memory CD8+T cells.HRD-positive patients had a worse prognosis and shorter progressionfree survival(PFS)to targeted therapy(first-and third-generation EGFR-TKIs)(P=0.042).Additionally,HRDpositive,EGFR/ALK wild-type patients showed a numerically lower response to platinum-free immunotherapy regimens.Conclusions:Unique genomic and transcriptional characteristics were found in HRD-positive NSCLC.Poor prognosis and poor response to EGFR-TKIs and immunotherapy were observed in HRD-positive NSCLC.This study highlights potential actionable alterations in HRD-positive NSCLC,suggesting possible combinational therapeutic strategies for these patients.

Low testing rates and high BRCA prevalence: Poly (ADP-ribose) polymerase inhibitor use in Middle East BRCA/homologous recombination deficiency-positive cancer patients

BACKGROUND Poly(ADP-ribose)polymerase inhibitors(PARPis)are approved as first-line therapies for breast cancer gene(BRCA)-positive,human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer.They are also effective for new and recurrent ovarian cancers that are BRCA-or homologous recombination deficiency(HRD)-positive.However,data on these mutations and PARPi use in the Middle East are limited.AIM To assess BRCA/HRD prevalence and PARPi use in patients in the Middle East with breast/ovarian cancer.METHODS This was a single-center retrospective study of 57 of 472 breast cancer patients tested for BRCA mutations,and 25 of 65 ovarian cancer patients tested for HRD.These adult patients participated in at least four visits to the oncology service at our center between August 2021 and May 2023.Data were summarized using descriptive statistics and compared using counts and percentages.Response to treatment was assessed using Response Evaluation Criteria in Solid Tumors criteria.RESULTS Among the 472 breast cancer patients,12.1%underwent BRCA testing,and 38.5%of 65 ovarian cancer patients received HRD testing.Pathogenic mutations were found in 25.6%of the tested patients:26.3%breast cancers had germline BRCA(gBRCA)mutations and 24.0%ovarian cancers showed HRD.Notably,40.0%of gBRCA-positive breast cancers and 66.0%of HRD-positive ovarian cancers were Middle Eastern and Asian patients,respectively.PARPi treatment was used in 5(33.3%)gBRCA-positive breast cancer patients as first-line therapy(n=1;7-months progression-free),for maintenance(n=2;>15-months progression-free),or at later stages due to compliance issues(n=2).Four patients(66.6%)with HRD-positive ovarian cancer received PARPi and all remained progression-free.CONCLUSION Lower testing rates but higher BRCA mutations in breast cancer were found.Ethnicity reflected United Arab Emirates demographics,with breast cancer in Middle Eastern and ovarian cancer in Asian patients.

Association between homologous recombination deficiency and outcomes with platinum and platinum-free chemotherapy in patients with triple-negative breast cancer

Objective:The choice of chemotherapeutic regimen for triple-negative breast cancer(TNBC)remains controversial.Homologous recombination deficiency(HRD)has attracted increasing attention in informing chemotherapy treatment.This study was aimed at investigating the feasibility of HRD as a clinically actionable biomarker for platinum-containing and platinum-free therapy.Methods:Chinese patients with TNBC who received chemotherapy between May 1,2008 and March 31,2020 were retrospectively analyzed with a customized 3D-HRD panel.HRD positivity was defined by an HRD score≥30 or deleterious BRCA1/2 mutation.A total of 386 chemotherapy-treated patients with TNBC were screened from a surgical cohort(NCT01150513)and a metastatic cohort,and 189 patients with available clinical and tumor sequencing data were included.Results:In the entire cohort,49.2%(93/189)of patients were identified as HRD positive(40 with deleterious BRCA1/2 mutations and 53 with BRCA1/2 intact with an HRD score of≥30).In the first-line metastatic setting,platinum therapy was associated with longer median progression-free survival(mPFS)than platinum-free therapy[9.1 vs.3.0 months;hazard ratio(HR),0.43;95%confidence interval 0.22–0.84;P=0.01].Among HRD-positive patients,the mPFS was significantly longer in those treated with platinum rather than platinum-free therapy(13.6 vs.2.0 months;HR,0.11;P=0.001).Among patients administered a platinum-free regimen,HRD-negative patients showed a PFS significantly superior to that of HRD-positive patients(P=0.02;treatment-biomarker P-interaction=0.001).Similar results were observed in the BRCA1/2-intact subset.In the adjuvant setting,HRD-positive patients tended to benefit more from platinum chemotherapy than from platinum-free chemotherapy(P=0.05,P-interaction=0.02).Conclusions:HRD characterization may guide decision-making regarding the use of platinum treatment in patients with TNBC in both adjuvant and metastatic settings.

Homologous recombination in DNA repair and DNA damage tolerance

Homologous recombination （HR） comprises a series of interrelated pathways that function in the repair of DNA double-stranded breaks （DSBs） and interstrand crosslinks （ICLs）. In addition, recombination provides critical support for DNA replication in the recovery of stalled or broken replication forks, contributing to tolerance of DNA damage. A central core of proteins, most critically the RecA homolog Rad51, catalyzes the key reactions that typify HR： homology search and DNA strand invasion. The diverse functions of recombination are reflected in the need for context-specific factors that perform supplemental functions in conjunction with the core proteins. The inability to properly repair complex DNA damage and resolve DNA replication stress leads to genomic instability and contributes to cancer etiology. Mutations in the BRCA2 recombination gene cause predisposition to breast and ovarian cancer as well as Fanconi anemia, a cancer predisposition syndrome characterized by a defect in the repair of DNA interstrand crosslinks. The cellular functions of recombination are also germane to DNA-based treatment modalities of cancer, which target replicating cells by the direct or indirect induction of DNA lesions that are substrates for recombination pathways. This review focuses on mechanistic aspects of HR relating to DSB and ICL repair as well as replication fork support.

miR-506: a regulator of chemo-sensitivity through suppression of the RAD51-homologous recombination axis

Ovarian carcinoma is the most lethal gynecologic malignancy. Resistance to platinum is considered the major problem afecting prognosis. Our recent study established that micro RNA-506(mi R-506) expression was closely associated with progression-free survival and overall survival in two independent patient cohorts totaling 598 epithelial ovarian cancer cases. Further functional study demonstrated that mi R-506 could augment the response to cisplatin and olaparib through targeting RAD51 and suppressing homologous recombination in a panel of ovarian cancer cell lines. Systemic delivery of mi R-506 in an orthotopic ovarian cancer mouse model signiicantly augmented the cisplatin response, thus recapitulating the clinical observation. Therefore, mi R-506 plays a functionally important role in homologous recombination and has important therapeutic value for sensitizing cancer cells to chemotherapy, especially in chemo-resistant patients with attenuated expression of mi R-506.

The mutational pattern of homologous recombination(HR)-associated genes and its relevance to the immunotherapeutic response in gastric cancer

Objective:Currently,there is an urgent need to identify immunotherapeutic biomarkers to increase the benefit of immune checkpoint inhibitors(ICIs)for patients with gastric cancer(GC).Homologous recombination deficiency(HRD)can modify the tumor immune microenvironment by increasing the presence of tumor-infiltrating lymphocytes and therefore might serve as a biomarker of immunotherapeutic response.We aimed to analyze the mutational pattern of HR-associated genes in Chinese patients with GC and its relevance to the tumor immune profile and clinical immunotherapeutic response.Methods:A panel of 543 cancer-associated genes was used to analyze genomic profiles in a cohort comprising 484 Chinese patients with GC.Correlations between HR gene mutations and tumor immunity or clinical outcomes were identified via bioinformatic analysis using 2 GC genomic datasets(TCGA and MSK-IMPACT).Results:Fifty-one of the 484(10.54%)patients carried at least one somatic mutation in an HR gene;ATM(16/484,3.31%)was among the most frequently mutated HR genes in the Chinese cohort.Mutations in HR genes were associated with elevated tumor mutational burden,enhanced immune activity,and microsatellite instability status.In the MSK-IMPACT cohort comprising 49 patients with stomach adenocarcinoma or gastroesophageal junction adenocarcinoma treated with ICIs,patients with HR-mut GC(n=12)had significantly better overall survival than those with HR-wt GC(n=37)(log-rank test,P<0.05).Conclusions:Our data suggest that detection of somatic mutations in HR genes might aid in identifying patients who might benefit from immune checkpoint blockade therapy.

Inhibition of KU70 and KU80 by CRISPR interference,not NgAgo interference,increases the efficiency of homologous recombination in pig fetal fibroblasts

Non-homologous end-joining(NHEJ) is a predominant pathway for the repair of DNA double-strand breaks(DSB). It inhibits the efficiency of homologous recombination(HR) by competing for DSB targets. To improve the efficiency of HR, multiple CRISPR interference(CRISPRi) and Natronobacterium gregoryi Argonaute(NgAgo) interference(NgAgoi) systems have been designed for the knockdown of NHEJ key molecules, KU70, KU80, polynucleotide kinase/phosphatase(PNKP), DNA ligase IV(LIG4), and NHEJ1. Suppression of KU70 and KU80 by CRISPRi dramatically promoted(P<0.05) the efficiency of HR to 1.85-and 1.58-fold, respectively, whereas knockdown of PNKP, LIG4, and NHEJ1 repair factors did not significantly increase(P>0.05) HR efficiency. Interestingly, although the NgAgoi system significantly suppressed(P<0.05) KU70, KU80, PNKP, LIG4, and NHEJ1 expression, it did not improve(P>0.05) HR efficiency in primary fetal fibroblasts. Our result showed that both NgAgo and catalytically inactive Cas9(dCas9) could interfere with the expression of target genes, but the downstream factors appear to be more active following CRISPR-mediated interference than that of NgAgo.

Construction of recombinant industrial Saccharomyces cerevisiae strain with bglS gene insertion into PEP4 locus by homologous recombination

The bglS gene encoding endo-1,3-1,4-β-glucanase from Bacillus subtil＆ was cloned and sequenced in this study. The bglS expression cassette, including PGK1 promoter, bglS gene fused to the signal sequence of the yeast mating pheromone a-factor （MFals）, and ADH1 terminator with G418-resistance as the selected marker, was constructed. Then one of the PEP4 allele of Saccharomyces cerevisiae WZ65 strain was replaced by bglS expression cassette using chromosomal integration of polymerase chain reaction （PCR）-mediated homologous recombination, and the bglS gene was expressed simultaneously. The recombinant strain S. cerevisiae （SC-βG） was preliminarily screened by the clearing hydrolysis zone formed after the barley β-glucan was hydrolyzed in the plate and no proteinase A （PrA） activity was measured in fermenting liquor. The results of PCR analysis of genome DNA showed that one of the PEP4 allele had been replaced and bglS gene had been inserted into the locus of PEP4 gene in recombinant strains. Different endo-1,3-1,4-β-glucanase assay methods showed that the recombinant strain SC-βG had high endo-1,3-1,4-β-glucanase expression level with the maximum of 69.3 U/（h·ml） after 60 h of incubation. Meanwhile, the Congo Red method was suitable for the determination of endo-1,3-1,4-β-glucanase activity during the actual brewing process. The current research implies that the constructed yeast strain could be utilized to improve the industrial brewing property of beer.

BLM helicase inhibition synergizes with PARP inhibition to improve the radiosensitivity of olaparib resistant non-small cell lung cancer cells by inhibiting homologous recombination repair

Objective:We aimed to investigate the radiosensitizing efficacy of the poly-ADP-ribose polymerase(PARP)inhibitor,olaparib,and the Bloom syndrome protein(BLM)helicase inhibitor,ML216,in non-small cell lung cancer(NSCLC)cells.Methods:Radiosensitization of NSCLC cells was assessed by colony formation and tumor growth assays.Mechanistically,the effects of ML216,olaparib,and radiation on cell and tumor proliferation,DNA damage,cell cycle,apoptosis,homologous recombination(HR)repair,and non-homologous end joining(NHEJ)repair activity were determined.Results:Both olaparib and ML216 enhanced the radiosensitivities of olaparib-sensitive H460 and H1299 cells,which was seen as decreased surviving fractions and Rad51 foci,increased total DNA damage,andγH2AX and 53BP1 foci(P<0.05).The expressions of HR repair proteins were remarkably decreased in olaparib-treated H460 and H1299 cells after irradiation(P<0.05),while olaparib combined with ML216 exerted a synergistic radiosensitization effect on olaparib-resistant A549 cells.In addition to increases of double strand break(DSB)damage and decreases of Rad51 foci,olaparib combined with ML216 also increased pDNA-PKcs(S2056)foci,abrogated G2 cell cycle arrest,and induced apoptosis in A549 lung cancer after irradiation in vitro and in vivo(P<0.05).Moreover,Western blot showed that olaparib combined with ML216 and irradiation inhibited HR repair,promoted NHEJ repair,and inactivated cell cycle checkpoint signals both in vitro and in vivo(P<0.05).Conclusions:Taken together,these results showed the efficacy of PARP and BLM helicase inhibitors for radiosensitizing NSCLC cells,and supported the model that BLM inhibition sensitizes cells to PARP inhibitor-mediated radiosensitization,as well as providing the basis for the potential clinical development of this combination for tumors intrinsically resistant to PARP inhibitors and radiotherapy.

Maternal gene Ooep may participate in homologous recombination-mediated DNA double-strand break repair in mouse oocytes

DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB repair plays dominant roles in safeguarding oocyte quantity and quality. However, little is known regarding the key players of the HR repair pathway in oocytes. Here, we identified oocyte-specific gene Ooep as a novel key component of the HR repair pathway in mouse oocytes. OOEP was required for efficient ataxia telangiectasia mutated （ATM） kinase activation and Rad51 recombinase （RAD51） focal accumulation at DNA DSBs. Ooep null oocytes were defective in DNA DSB repair and prone to apoptosis upon exogenous DNA damage insults. Moreover, Ooep null oocytes exhibited delayed meiotic maturation. Therefore, OOEP played roles in preserving oocyte quantity and quality by maintaining genome stability. Ooep expression decreased with the advance of maternal age, suggesting its involvement in maternal aging.

Phylogeny and Homologous Recombination Occurring in Classical Swine Fever Viruses

Classical swine fever virus(CSFV) is the causative agent of classical swine fever, a highly contagious disease of pigs. But there is little information on the recombination in natural populations of CSFVs. Therefore, a phylogenetic analysis of 62 fulllength genome CSFV strains, isolated from all over the world, was performed to detect potential recombination events, with the recombinant sequences being analyzed with the SimPlot and RDP programs. The results identified a mosaic virus, Chinese CSFV HCLV(2)(AF091507.1), which is the one naturally emerged recombinant CSFV with two recombination breakpoints at 2 484 and 2 900 bp of the genome alignment. Its two putative parental-like strains were CSFV Shimen(AF092448.2) and CSFV strain C/HVRI(AY805221.1). This work demonstrated that homologous recombination did occur in natural CSFV populations. It had significant implications for understanding the molecular epidemiology of CSFV, and revealed that recombination was an important factor for high genetic diversities of CSFV.

Phylogeny and Homologous Recombination in Japanese Encephalitis Viruses

Japanese encephalitis virus（JEV） is a significant causative agent of arthropod-borne encephalitis and what is less clear that the factors cause the virus wide spread. The objective was to confirm whether the homologous recombination imposed on JEV. The phylogenetic and homologous recombination analyses were performed based on 163 complete JEV genomes which were recently isolated. They were still separated into five genotypes（GI-GV） and the most of recently isolated JEVs were GI rather than GIII in Asian areas including China's Mainland. Two recombinant events were identified in JEV and the evidence of the recombination was observed between China and Japan isolates that partitioned into two distinct subclades, but still the same genotype（GIII）. Our data further suggested that most of the nucleotides in JEV genome were under negative selection; however, changes within codon 2 316（amino acid NS4b-44） showed an evidence of the positive selection.

Caseinolytic mitochondrial matrix peptidase X is essential for homologous chromosome synapsis and recombination during meiosis of male mouse germ cells

Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins.The mitochondrial protease complex(ClpXP),which consists of caseinolytic mitochondrial matrix peptidase X(ClpX)and caseinolytic protease P(ClpP)and mediates the degradation of misfolded,damaged,and oxidized proteins,is essential for maintaining mitochondrial homeostasis.ClpXP has been implicated in meiosis regulation,but its precise role is currently unknown.In this study,we engineered an inducible male germ cell-specific knockout caseinolytic mitochondrial matrix peptidase X(Clpx^(cKO))mouse model to investigate the function of ClpX in meiosis.We found that disrupting Clpx in male mice induced germ cell apoptosis and led to an absence of sperm in the epididymis.Specifically,it caused asynapsis of homologous chromosomes and impaired meiotic recombination,resulting in meiotic arrest in the zygotene-to-pachytene transition phase.The loss of ClpX compromised the double-strand break(DSB)repair machinery by markedly reducing the recruitment of DNA repair protein RAD51 homolog 1(RAD51)to DSB sites.This dysfunction may be due to an insufficient supply of energy from the aberrant mitochondria in Clpx^(cKO) spermatocytes,as discerned by electron microscopy.Furthermore,ubiquitination signals on chromosomes and the expression of oxidative phosphorylation subunits were both significantly attenuated in Clpx^(cKO) spermatocytes.Taken together,we propose that ClpX is essential for maintaining mitochondrial protein homeostasis and ensuring homologous chromosome pairing,synapsis,and recombination in spermatocytes during meiotic prophase I.

ILF3 safeguards telomeres from aberrant homologous recombination as a telomeric R-loop reader

Telomeres are specialized structures at the ends of linear chromosomes that protect genome stability.The telomeric repeat-containing RNA(TERRA)that is transcribed from subtelomeric regions can invade into double-stranded DNA regions and form RNA:DNA hybrid-containing structure called R-loop.In tumor cells,R-loop formation is closely linked to gene expression and the alternative lengthening of telomeres(ALT)pathway.Dysregulated R-loops can cause stalled replication forks and telomere instability.However,how R-loops are recognized and regulated,particularly at telomeres,is not well understood.We discovered that ILF3 selectively associates with telomeric R-loops and safeguards telomeres from abnormal homologous recombination.Knocking out ILF3 results in excessive R-loops at telomeres and triggers telomeric DNA damage responses.In addition,ILF3 deficiency disrupts telomere homeostasis and causes abnormalities in the ALT pathway.Using the proximity-dependent biotin identification(BioID)technology,we mapped the ILF3 interactome and discovered that ILF3 could interact with several DNA/RNA helicases,including DHX9.Importantly,ILF3 may aid in the resolution of telomeric R-loops through its interaction with DHX9.Our findings suggest that ILF3 may function as a reader of telomeric R-loops,helping to prevent abnormal homologous recombination and maintain telomere homeostasis.

TP53-specific mutations serve as a potential biomarker for homologous recombination deficiency in breast cancer:a clinical next-generation sequencing study

Background:TP53 mutations and homologous recombination deficiency(HRD)occur frequently in breast cancer.However,the characteristics of TP53 pathogenic mutations in breast cancer patients with/without HRD are not clear.Methods:Clinical next-generation sequencing(NGS)of both tumor and paired blood DNA from 119 breast cancer patients(BRCA-119 cohort)was performed with a 520-gene panel.Mutations,tumor mutation burden(TMB),and genomic HRD scores were assessed from NGS data.NGS data from 47 breast cancer patients in the HRD test cohort were analyzed for further verification.Results:All TP53 pathogenic mutations in patients had somatic origin,which was associated with the protein expression of estrogen receptor and progestogen receptor.Compared to patients without TP53 pathologic mutations,patients with TP53 pathologic mutations had higher levels of HRD scores and different genomic alterations.The frequency of TP53 pathologic mutation was higher in the HRDhigh group(HRD score≥42)relative to that in the HRD-low group(HRD score<42).TP53 has different mutational characteristics between the HRD-low and HRD-high groups.TP53-specific mutation subgroups had diverse genomic features and TMB.Notably,TP53 pathogenic mutations predicted the HRD status of breast cancer patients with an area under the curve(AUC)of 0.61.TP53-specific mutations,namely HRD-low mutation,HRD-high mutation,and HRD common mutation,predicted the HRD status of breast cancer patients with AUC values of 0.32,0.72,and 0.58,respectively.Interestingly,TP53 HRD-high mutation and HRD common mutation combinations showed the highest AUC values(0.80)in predicting HRD status.Conclusions:TP53-specific mutation combinations predict the HRD status of patients,indicating that TP53 pathogenic mutations could serve as a potential biomarker for poly-ADP-ribose polymerase(PARP)inhibitors in breast cancer patients.

A method to synthesize cDNA constructs by homology based recombination cloning

We introduce a homology-based recombination approach for generating a cDNA construct. This method depends on amplifying several exon fragments and their fusions by the homology-based recombination. This method provides a way to generate the cDNA sequence of any gene without any need for its mRNA. The paper describes the strategy by assembling cDNA of the MYB1 and MYB2 genes of Arabidopsis thaliana.

Double-stranded DNA breaks and gene functions in recombination and meiosis

Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.

The Role of DNA Mismatch Repair and Recombination in the Processing of DNA Alkylating Damage in Living Yeast Cells

It is proposed that mismatch repair (MMR) mediates the cytotoxic effects of DNA damaging agents by exerting a futile repair pathway which leads to double strand breaks (DSBs). Previous reports indicate that the sensitivity of cells defective in homologous recombination (HR) to DNA alkylation is reduced by defects in MMR genes. We have assessed the contribution of different MMR genes to the processing of alkylation damage in vivo. We have directly visualized recombination complexes formed upon DNA damage using fluorescent protein (FP) fusions. We find that msh6 mutants are more resistant than wild type cells to MNNG, and that an msh6 mutation rescues the sensitivity of rad52 strains more efficiently than an msh3 mutation. Analysis of RAD52-GFP tagged strains indicate that MNNG increases repair foci formation, and that the inactivation of the MHS2 and MSH6 genes but not the MSH3 gene result in a reduction of the number of foci formed. In addition, in the absence of HR, NHEJ could process the MNNG-induced DSBs as indicated by the formation of NHEJ-GFP tagged foci. These data suggest that processing of the alkylation damage by MMR, mainly by MSH2-MSH6, is required for recruitment of recombination proteins to the damage site for repair.

Construction of Gpm6a/ReelinGFPCreERT2 by BAC recombination using a specific gene in hepatic mesothelial or stellate cells

AIM To prepare a Gpm6a/Reelin^(GFPCreERT2) construct with a rapid and reliable strategy using a bacterial artificial chromosome(BAC). METHODS Gpm6 a and Reelin BACs were purified and transformed into SW102 E. coli by electroporation. The GFPCreE RT2 fragment was prepared from a shuttle vector and transformed into SW102 E. coli carrying a BAC. Homologous recombination was induced in SW102 E. coli. Recombinant clones were screened and confirmed by PCR and restriction enzyme digestion. Recombinant clones were transformed into SW102 E. coli to remove the kanamycin unit.RESULTS A complete BAC was successfully transformed into SW102 E. coli by electroporation because BAC purified from SW102 E. coli showed the same pattern as the original BAC with Bam H I digestion. The GFPCre ERT2 fragment was deemed to have been prepared successfully because we obtained the same size fragment as expected. Homologous recombination was induced, and GFPCre ERT2 was deemed to have been inserted into the correct site of the BAC because we found the band change was the same as the expected pattern after restriction enzyme digestion. The kanamycin unit was deemed to have been removed successfully because we obtained different sizes of bands that were consistent with the results expected by PCR with different primers. CONCLUSION The construct of Gpm6 a^(GFPCreERT2) or Reelin^(GFPCreERT2) was prepared successfully, which will establish a foundation for tracing the hepatic stellate cell lineage and studying its function.

Rapid construction of phosphatase and tensin homolog-deleted on chromosome ten gene recombinant adenovirus using the AdEasy system

Recent studies have shown that phosphatase and tensin homolog-deleted on chromosome ten （PTEN） gene plays an important role in ischemic brain damage and synaptic plasticity. The AdEasy system, which has been widely used, greatly simplifies preparation of recombinant adenovirus. Therefore, recombinant defective adenovirus vector carrying human PTEN tumor suppressor gene （Ad-PTEN） was constructed using the AdEasy-1 system and was transfected into HEK293 cells for packaging and amplification. Infection efficiency and expression intensity were observed in primary cultured rat hippocampal neurons infected with Ad-PTEN in vitro. Results revealed a cytopathic effect in green fluorescent protein expression, which increased with prolonged time. After three cycles of amplification, the adenovirus titer was increased to an adequate titer for infecting hippocampal neurons. The entire process typically requires 4-5 weeks for completion. Results suggested that recombinant defective adenovirus vector carrying the PTEN gene was successfully and rapidly constructed using the AdEasy system.