The generation of a tau-V337M point mutation mouse model using gene editing technology can provide an animal model with fast disease progression and more severe symptoms, which facilitate the study of pathogenesis and treatment of Alzheimer's disease (AD). In this study, single guide RNAs (sgRNA) and single-stranded oligonucleotides (ssODN) were designed and synthesized in vitro. The mixture of sgRNA, Cas9 protein and ssODN was microinjected into the zygotes of C57BL/6J mice. After DNA cutting and recombination, the site homologous to human 337 valine (GTG) in exon 11 was mutated into methionine (ATG). In order to improve the efficiency of recombination, a Rad51 protein was added. The female mice mated with the nonvasectomy male mice were used as the surrogates. Subsequently, the 2-cell stage gene edited embryos were transferred into the unilateral oviduct, and the F0 tau-V337M mutation mice were obtained. Higher mutation efficiency could be obtained by adding Rad51 protein. The F0 tau-V337M point mutation mice can pass the mutation on to the F1 generation mice. In conclusion, this study successfully established the first tau-V337M mutation mouse by using Cas9, ssODN and Rad51. These results provide a new method for developing AD mice model which can be used in further research on the pathogenesis and treatment of AD.
Animals ; Male ; Female ; Mice ; Humans ; CRISPR-Cas Systems/genetics* ; RNA, Guide, CRISPR-Cas Systems ; Rad51 Recombinase/genetics* ; Mice, Inbred C57BL ; Disease Models, Animal ; Recombination, Genetic

OBJECTIVE: To investigate the recombinations within the human leukocyte antigen (HLA) region in two families. METHODS: Genomic DNA was extracted from the peripheral blood specimens of the different family members. HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1 loci were genotyped using polymerase chain reaction-sequence specific oligonucleotide probing technique (PCR-SSO) and next-generation sequencing technique. HLA haplotype was determined by genetic analysis of the pedigree. RESULTS: The haplotypes of HLA-A*11:01~C*03:04~B*13:01~DRB1*12:02~DQB1*03:01~DPB1*05:01:01G and HLA-A*03:01~C*04:01~B*35:03~DRB1*12:01~DQB1*03:01~DPB1*04:01:01G in the family 1 were recombined between HLA-B and HLA-DRB1 loci, which formed the haplotype of HLA-A*11:01~C*03:04~B*13:01~DRB1* 12:01~DQB1*03:01~DPB1*04:01:01G. The haplotypes of HLA-A *02:06~C*03:03~B*35:01~DRB1*08:02~DQB1*04:02~ DPB1*13:01:01G and HLA-A *11:01~C*07:02~B*38:02~DRB1*15:02~DQB1*05:01~DPB1*05:01:01G in the family 2 were recombined between HLA-DQB1 and HLA-DPB1 loci, which formed the haplotype of HLA-A*02:06~C*03:03~B*35:01~ DRB1*08:02~DQB1*04:02~DPB1*05:01:01G. CONCLUSION The gene recombination events between HLA-B and -DRB1, HLA-DQB1 and -DPB1 loci were found respectively in two Chinese Han families.
Humans ; Gene Frequency ; HLA-DQ beta-Chains/genetics* ; HLA-B Antigens/genetics* ; Histocompatibility Antigens Class I/genetics* ; Haplotypes ; HLA-A Antigens/genetics* ; HLA-DRB1 Chains/genetics* ; Recombination, Genetic ; Alleles

OBJECTIVE: To analyze the molecular characteristics of a recombinant allele of the ABO blood group. METHODS: The ABO phenotype was determined with the tube method. The coding regions of the ABO and FUT1 genes were analyzed by PCR-sequence based typing. The ABO alleles of the proband were determined by allele-specific primer sequencing. The full sequences of the ABO gene of the proband and her mother were determined through next generation sequencing. RESULTS: The red blood cells of the proband did not agglutinate with anti-H, and the sequence of the FUT1 gene was homozygous for c.551_552delAG.The proband was thereby assigned as para-Bombay. Bi-directional sequencing also found that she was heterozygous for c.261G/del,467C>T,c.526C>G,c.657C>T,c.703G>A,c.796C>A,c.803G>C and c.930G>A of the coding regions of the ABO gene. Allele-specific primer sequencing also found her to carry a ABO*A1.02 allele and a recombinant allele from ABO*O.01.01 and ABO*B.01. The recombination site was located between nucleotide c.375-269 and c.526, and the allele was maternally derived. CONCLUSION An recombinant allele of the ABO gene has been identified, which has originated from recombination of ABO*O.01.01 with the ABO*B.01 allele.
ABO Blood-Group System/genetics* ; Alleles ; Blood Grouping and Crossmatching ; Female ; Fucosyltransferases/genetics* ; Genotype ; Humans ; Phenotype ; Recombination, Genetic

Repairing DNA double-strand breaks (DSBs) with homologous chromosomes as templates is the hallmark of meiosis. The critical outcome of meiotic homologous recombination is crossovers, which ensure faithful chromosome segregation and promote genetic diversity of progenies. Crossover patterns are tightly controlled and exhibit three characteristics: obligatory crossover, crossover interference, and crossover homeostasis. Aberrant crossover patterns are the leading cause of infertility, miscarriage, and congenital disease. Crossover recombination occurs in the context of meiotic chromosomes, and it is tightly integrated with and regulated by meiotic chromosome structure both locally and globally. Meiotic chromosomes are organized in a loop-axis architecture. Diverse evidence shows that chromosome axis length determines crossover frequency. Interestingly, short chromosomes show different crossover patterns compared to long chromosomes. A high frequency of human embryos are aneuploid, primarily derived from female meiosis errors. Dramatically increased aneuploidy in older women is the well-known "maternal age effect." However, a high frequency of aneuploidy also occurs in young women, derived from crossover maturation inefficiency in human females. In addition, frequency of human aneuploidy also shows other age-dependent alterations. Here, current advances in the understanding of these issues are reviewed, regulation of crossover patterns by meiotic chromosomes are discussed, and issues that remain to be investigated are suggested.
Cell Division/physiology* ; Chromosome Segregation/physiology* ; Humans ; Meiosis/genetics* ; Recombination, Genetic

recombination deficiency (HRD) genes, because BRCA/HRD mutations (BRCA/HRDm) are known to be associated with better prognosis.RESULTS: Enrollment was slow, accrual was closed when 7+ years had passed. With a median follow-up of 88.9 months, the median PFS was significantly better in arm A (55.5 months) than arm B (9.2 months) (hazard ratio [HR]=0.40; 95% confidence interval [CI]=0.19–0.87; p=0.020), yet the median overall survival was not significantly different in arm A (not reached) than arm B (95.1 months) (p=0.148). Overall grade 3/4 adverse events were more frequent in arm A than arm B (60.9% vs 0.0%) (p<0.001). Quality of life was generally not significantly different. Distribution of BRCA1/2m or BRCA/HRDm was not significantly biased between the two arms. Wild-type BRCA/non-HRD subgroup seemed to fare better with maintenance therapy (HR=0.35; 95% CI=0.11–1.18; p=0.091).CONCLUSIONS: Despite limitations in small sample size, it suggests that maintenance carboplatin-PLD chemotherapy could improve PFS in advanced ovarian cancer.]]>
Arm ; Asian Continental Ancestry Group ; Bias (Epidemiology) ; Carboplatin ; Disease-Free Survival ; Doxorubicin ; Drug Therapy ; Follow-Up Studies ; Humans ; Maintenance Chemotherapy ; Ovarian Neoplasms ; Prognosis ; Quality of Life ; Recombination, Genetic ; Sample Size

Enterovirus species G (EV-G) is highly diverse, and is ubiquitous in pig populations, usually without diarrhea. The present study aimed to investigate the presence of novel EV-G recombinants with the torovirus papain-like cysteine protease (PLCP) in Jeju pig herds. EV-G1-PLCP mono-infections were most prevalent in diarrheic weaned piglets. The PLCP genes of the Jeju isolates varied in size and junction sequences, and were greatly heterogeneous, with 77.0–90.7% homology amongst all recombinants. Our results suggest that the exogenous PLCP gene has undergone continuous rapid mutation in the individual EV-G genomes following cross-order recombination, thereby causing clinical disease in swine.
Cysteine Proteases ; Diarrhea ; Enterovirus ; Genome ; Korea ; Prevalence ; Recombination, Genetic ; Swine ; Torovirus

Two infectious bronchitis virus (IBV) K046-12 and K047-12 strains were isolated and the nearly complete genomes of them were sequenced. Sequence comparisons showed that the K046-12 genome was most similar to Korean IBV strains, and the K047-12 genome was most similar to QX-like IBV strains. Phylogenetic analysis showed that nearly all K046-12 and most K046-12 genes were placed in the same cluster as Korean IBV isolates, but the S1 region was placed in the same cluster as Mass-type IBVs. For K047-12, nearly all K047-12 and most K047-12 genes were located in the same cluster as QX-like IBVs, but the M region was located in the same cluster as Korean IBV isolates with K047-12. Recombination analysis confirmed that K046-12 is a recombinant strain with the primary parental sequence derived from Korean IBVs and minor parental sequence derived from Mass-type IBV, and K047-12 is a recombinant strain with the major parental sequence derived from QX-IBV and minor parental sequence derived from Korean IBVs. This study showed that new IBV recombinants are constantly generated among various IBVs, including those used for vaccination. Therefore, genetic analysis of new virus isolates should be performed for effective infectious bronchitis control and appropriate vaccine development.
Bronchitis ; Genome ; Humans ; Infectious bronchitis virus ; Korea ; Parents ; Recombination, Genetic ; Vaccination

Exonuclease Ⅷ (Exo Ⅷ), an ATP-independent dsDNA 5'-3' exonuclease, is a candidate protein with great application value for in vitro DNA recombination. However, the application of Exo Ⅷ in DNA recombination in vitro has not been reported. In this study, the recombinant expression vector of the truncated Exo Ⅷ (tExo Ⅷ) with the full exonuclease activity was built and used to achieve the overexpression of tExo Ⅷ in Escherichia coli. Based on the purified tExo Ⅷ protein with high-purity, the feasibility of tExo Ⅷ applied in vitro DNA recombination and effects of the reaction temperatures, reaction duration, and homology arm lengths were examined. The results showed that tExo Ⅷ was highly expressed in soluble form in E. coli. One liter of bacterial culture yielded 92.40 mg of purified tExo Ⅷ with the specific activity of 1.21×10⁵ U/mg. In a 10 μL recombination system containing 2.5 U tExo Ⅷ, the highest cloning efficiency was achieved in a reaction at 25 °C for 12.5 min and followed by incubation at 50 °C for 50 min. With addition of Pfu DNA polymerase, the homology arm extension strategy can effectively improve the recombination efficiency. Using competent E. coli Mach1 T1 with 2.2×10⁶ cfu/μg transformation efficiency as recipient cell, the recombination of a 1 kb fragment with a 21 bp homology arm and a 5.8 kb linearized vector can form about 1.1×10⁴ recombinant clones per μg vector, and the positive rates was over 80%. The recombination efficiency was increased with the increasing length of homology arm ranged from 8 to 21 bp. Under the optimal reaction condition, only 8 bp homology arm can still achieve valid DNA recombination. This novel in vitro DNA recombination system mediated by tExo Ⅷ was particularly characterized by its easy preparation, no limitation on restriction sites and high recombination cloning efficiency. All results revealed that the new efficient gene cloning system has potential application in the field of molecular biology.
Cloning, Molecular ; Escherichia coli ; genetics ; Exonucleases ; genetics ; Recombinant Proteins ; metabolism ; Recombination, Genetic

Isovalerylspiramycin (ISP)Ⅰ, as a major component of bitespiramycin (BT), exhibits similar antimicrobial activities with BT and has advantages in quality control and dosage forms. It has been under preclinical studies. The existing ISPⅠ producing strain, undergoing three genetic modifications, carries two resistant gene markers. Thus, it is hard for further genetic manipulation. It is a time-consuming and unsuccessful work to construct a new ISPⅠ strain without resistant gene marker by means of the classical homologous recombination in our preliminary experiments. Fortunately, construction of the markerless ISPⅠ strain, in which the bsm4 (responsible for acylation at 3 of spiramycin) gene was replaced by the Isovaleryltansferase gene (ist) under control of the constitutive promoter ermEp*, was efficiently achieved by using the CRISPR-Cas9 gene editing system. The mutant of bsm4 deletion can only produce SPⅠ. Isovaleryltransferase coded by ist catalyzes the isovalerylation of the SPⅠat C-4" hydroxyl group to produce ISPⅠ. As anticipated, ISPⅠ was the sole ISP component of the resultant strain (ΔEI) when detected by HPLC and mass spectrometry. The ΔEI mutant is suitable for further genetic engineering to obtain improved strains by reusing CRISPR-Cas9 system.
CRISPR-Cas Systems ; Gene Editing ; Genetic Engineering ; Homologous Recombination

Seamless modification is a popular genomic manipulation technique in genetic engineering. Selection stringency of the counter-selection system determines the efficiency of the seamless modification. Recently, a novel counter-selection system, kil, was constructed. It is reported that the selection selectivity of kil is higher in host bacteria harboring plasmid pSim6 than that harboring pKD46, indicating that recombinants could be selected out more efficiently by combining kil counter-selection system and plasmid pSim6. In order to confirm this speculation, four different loci (lacI, dbpa, ack, glk) in Escherichia coli strains W3110, MG1655 and DH10B were selected for testing: dsDNA fragments of different sizes (500 bp, 1 000 bp, and 2 000 bp) were used to substitute tet/kil. As expected, recombination efficiency was higher in host bacteria harboring plasmid pSim6 than that harboring pKD46, and the results were more obvious with the length of dsDNA increasing. Specifically, recombination efficiency was 1.2 to 2 fold higher in pSim6 harboring bacteria than in pKD46 harboring bacteria when dsDNA fragments were 1 000 bp in length. With the length of dsDNA increasing up to 2 000 bp, the gap increased to 2.2-5 fold. In conclusion, it is easier to perform seamless modification by combining kil counter-selection system and plasmid pSim6 than combining kil and pKD46. An alternative tool in genomic engineering is provided in this study.
Escherichia coli ; Escherichia coli Proteins ; Genetic Engineering ; Plasmids ; Recombination, Genetic