Promoter engineering enables precise metabolic regulation towards efficient β-elemene production in Ogataea polymorpha

Precisely controlling gene expression is beneficial for optimizing biosynthetic pathways for improving the production. However, promoters in nonconventional yeasts such as Ogataea polymorpha are always limited, which results in incompatible gene modulation. Here, we expanded the promoter library in O. polymorpha based on transcriptional data, among which 13 constitutive promoters had the strengths ranging from 0-55% of PGAP, the commonly used strong constitutive promoter, and 2 were growth phase-dependent promoters. Subsequently, 2 hybrid growth phase-dependent promoters were constructed and characterized, which had 2-fold higher activities. Finally, promoter engineering was applied to precisely regulate cellular metabolism for efficient production of β-elemene. The glyceraldehyde-3-phosphate dehydrogenase gene GAP was downregulated to drive more flux into pentose phosphate pathway (PPP) and then to enhance the supply of acetyl-CoA by using phosphoketolase-phosphotransacetylase (PK-PTA) pathway. Coupled with the phase-dependent expression of synthase module (ERG20∼LsLTC2 fusion), the highest titer of 5.24 g/L with a yield of 0.037 g/(g glucose) was achieved in strain YY150U under fed-batch fermentation in shake flasks. This work characterized and engineered a series of promoters, that can be used to fine-tune genes for constructing efficient yeast cell factories.

Ogataea polymorpha as a next-generation chassis for industrial biotechnology

Ogataea (Hansenula) polymorpha is a nonconventional yeast with some unique characteristics, including fast growth, thermostability, and broad substrate spectrum. Other than common applications for protein production, O. polymorpha is attracting interest for chemical and protein production from methanol; a promising feedstock for the next-generation biomanufacturing due to its abundant sources and excellent characteristics. Benefiting from the development of synthetic biology, it has been engineered to produce value-added chemicals by extensively rewiring cellular metabolism. This Review discusses recently developed synthetic biology tools of O. polymorpha. The advances of chemicals production and systems biology were reviewed comprehensively. Finally, we look ahead to the developments of biomanufacturing in O. polymorpha to make an overall understanding of this chassis for academia and industry.

Synthetic biology for Taxol biosynthesis and sustainable production

Incomplete understanding of the biosynthetic pathway of the anticancer compound Taxol hinders its production by metabolic engineering. Recent reports by Jiang et al. and other groups now describe the missing steps in Taxol biosynthesis, notably including oxetane ring formation. These findings will promote the sustainable production of Taxol through synthetic biology.

De novo biosynthesis of the hops bioactive flavonoid xanthohumol in yeast

The flavonoid xanthohumol is an important flavor substance in the brewing industry that has a wide variety of bioactivities. However, its unstable structure results in its low content in beer. Microbial biosynthesis is considered a sustainable and economically viable alternative. Here, we harness the yeast Saccharomyces cerevisiae for the de novo biosynthesis of xanthohumol from glucose by balancing the three parallel biosynthetic pathways, prenyltransferase engineering, enhancing precursor supply, constructing enzyme fusion, and peroxisomal engineering. These strategies improve the production of the key xanthohumol precursor demethylxanthohumol (DMX) by 83-fold and achieve the de novo biosynthesis of xanthohumol in yeast. We also reveal that prenylation is the key limiting step in DMX biosynthesis and develop tailored metabolic regulation strategies to enhance the DMAPP availability and prenylation efficiency. Our work provides feasible approaches for systematically engineering yeast cell factories for the de novo biosynthesis of complex natural products.

Engineering co-utilization of glucose and xylose for chemical overproduction from lignocellulose

Bio-refining lignocellulose could provide a sustainable supply of fuels and fine chemicals; however, the challenges associated with the co-utilization of xylose and glucose typically compromise the efficiency of lignocellulose conversion. Here we engineered the industrial yeast Ogataea polymorpha (Hansenula polymorpha) for lignocellulose biorefinery by facilitating the co-utilization of glucose and xylose to optimize the production of free fatty acids (FFAs) and 3-hydroxypropionic acid (3-HP) from lignocellulose. We rewired the central metabolism for the enhanced supply of acetyl-coenzyme A and nicotinamide adenine dinucleotide phosphate hydrogen, obtaining 30.0 g l-1 of FFAs from glucose, with productivity of up to 0.27 g l-1 h-1. Strengthening xylose uptake and catabolism promoted the synchronous utilization of glucose and xylose, which enabled the production of 38.2 g l-1 and 7.0 g l-1 FFAs from the glucose-xylose mixture and lignocellulosic hydrolysates, respectively. Finally, this efficient cell factory was metabolically transformed for 3-HP production with the highest titer of 79.6 g l-1 in fed-batch fermentation in mixed glucose and xylose.

[Two cases of acute methyl acetate poisoning]

This article analyzed the clinical data and on-site occupational health survey results of a patient with occupational acute methyl acetate poisoning in Zhejiang. Based on the pathways of methyl acetate poisoning and the characteristics of target organ damage, diagnosis and treatment experience were summarized, providing reference for the diagnosis and treatment of occupational acute methyl acetate poisoning and occupational health monitoring of methyl acetate.

Occult Lymph Node Metastasis in cN0 Tongue Squamous Cell Carcinoma: A Prospective Observational Study

PURPOSE/OBJECTIVE(S)

Tongue squamous cell carcinoma (TSCC) is prone to occult lymph node metastasis, and preoperative evaluation of cervical nodes is critical for determining treatment strategies. There is scarce report of detecting occult lymph node metastasis in TSCC by using multi-parameter magnetic resonance imaging (mpMRI), spectral computed tomography (spectral CT) or other diagnostic functional imaging. In this study, we aimed to analyze the incidence and risk factors of occult lymph node metastasis in cN0 TSCC by comparing preoperative imaging with postoperative pathology results.

MATERIALS/METHODS

This study prospectively enrolled newly-diagnosed cN0 TSCC patients admitted to the Hunan Cancer Hospital between May, 2022 and December, 2022. All patients underwent primary resection and selective dissection of cervical lymph nodes. MpMRI and spectral CT scan of oral cavity and neck were performed prior to surgery. Preoperative evaluation of lymph node metastasis was conducted by two senior radiologists independently. The location of cervical lymph nodes was assigned based on the 2013 consensus guidelines.

RESULTS

A total of 26 cN0 TSCC patients (6 cT1 stage, 13 cT2 stage, and 7 cT3 stage) were enrolled. The median age was 53 (range, 36-64), and there were 25 males. Among all patients, 13 patients underwent unilateral cervical lymph node dissection, while 13 patients underwent bilateral cervical lymph node dissection. A total of 208 lymphatic drainage areas were resected, and 1003 lymph nodes were removed. There were 7 of pT1, 12 of pT2, 7 of pT3 based on postoperative pathological stages. Besides, there are 21 cases staged pN0, 2 cases staged pN1, 2 cases staged pN2, and 1 case staged pN3. Among the 26 patients, 5 (19.23%) cases had occult lymph node metastasis. A total of 8 metastatic lymph nodes (4 in ipsilateral Ib level, 1 in contralateral Ib level, 3 in IIa level ipsilateral side) were detected in the whole group. No lymph node metastasis was detected in level IIb, III and IV. The median maximum diameter of metastatic lymph nodes was 12 mm (range 5 to 15 mm), and 1 extra-nodal extension was observed. Moreover, all occult lymph node metastases occurred in patients with a primary invasion depth of ≥ 5 mm (29.41%, 5/17).

CONCLUSION

The incidence of occult lymph node metastasis in cN0 TSCC remains high under functional imaging diagnostic technology. Preventive neck dissection is necessary for patients with cN0 disease, especially those with primary tumor invasion depth exceeding 5 mm.

An improved CRISPRi system in Pichia pastoris

CRISPR interference (CRISPRi) has been developed and widely used for gene repression in various hosts. Here we report an improved CRISPRi system in Pichia pastoris by fusing dCas9 with endogenous transcriptional repressor domains. The CRISPRi system shows strong repression of eGFP, with the highest efficiency of 85%. Repression of native genes is demonstrated by targeting AOX1 promoter. AOX1 is efficiently repressed and the mutant strains show much slower growth in methanol medium. Effects of gRNA expression and processing on CRISPRi efficiency is also investigated. It is found that gRNA processing by HH/HDV ribozymes or Csy4 endoribonuclease generating clean gRNA is critical to achieve strong repression, and Csy4 cleavage shows higher repression efficiency. However, gRNA expression using native tRNA transcription and processing systems results in relatively weaker repression of eGFP. By expression of two gRNAs targeting promoters of eGFP and AOX1 in an array together with Cys4 recognition sites, both genes can be repressed simultaneously. Cys4-mediated gRNA array processing is further applied to repress fatty acyl-CoA synthetase genes (FAA1 and FAA2). Both genes are efficiently repressed, demonstrating that Cys4 endoribonuclease has the ability to cleave gRNAs array and can be can be used for multiplexed gene repression in P. pastoris.

[Clinical features of post-neurosurgical bacterial meningitis in children]

Objective: To understand the characteristics of bacterial meningitis after pediatric neurosurgical procedures. Methods: This was a retrospective observational study. From January 2016 to December 2022, 64 children diagnosed with post-neurosurgical bacterial meningitis based on positive cerebrospinal fluid (CSF) culture in Department of Neurosurgery of Shanghai Children's Medical Center were selected as the study population. The clinical characteristics, onset time, routine biochemical indexes of cerebrospinal fluid before anti infection treatment, bacteriology characteristics and sensitivity to antibiotics of bacteria cultured from cerebrospinal fluid were analyzed. Based on the CSF culture results, the patients were divided into the Gram-positive bacteria infection group and the Gram-negative bacteria infection group. The clinical characteristics of the two groups were compared using t-tests or Wilcoxon rank-sum tests, and chi-square tests. Results: There were 64 children,42 boys and 22 girls, with onset age of 0.83 (0.50, 1.75) years. Seventy cases of post-neurosurgical bacterial meningitis occurred in the 64 children, of which 15 cases (21%) in spring, 23 cases (33%) in summer, 19 cases (27%) in autumn, and 13 cases (19%) in winter. The time of onset was 3.5 (1.0, 10.0) months after surgery; 15 cases (21%) occurred within the first month after the surgery, and 55 cases (79%) occurred after the first month. There were 38 cases (59%) showing obvious abnormal clinical manifestations, fever 36 cases (56%), vomiting 11 cases (17%). Forty-eight cases (69%) were caused by Gram-positive bacteria, with Staphylococcus epidermidis 24 cases; 22 cases (31%) were caused by Gram-negative bacteria, with Acinetobacter baumannii the prominent pathogen 7 cases. The Gram-positive bacterial infection was more common in summer than the Gram-negative bacterial infection (20 cases (42%) vs. 3 cases (14%), χ²=5.37, P=0.020), while the Gram-negative bacterial infection was more in autumn and within the first month after surgery than the Gram-positive bacterial infection (11 cases (50%) vs. 8 cases (17%), 15 cases (67%) vs. 5 cases (33%), χ²=8.48, 9.02; P=0.004, 0.003). Gram-positive bacteria resistant to vancomycin and Acinetobacter baumannii resistant to polymyxin were not found. However, Acinetobacter baumannii showed only 45% (10/22) susceptibility to carbapenem antibiotics. Conclusions: The clinical presentation of post-neurosurgical bacterial meningitis in children is atypical. Gram-positive bacteria are the main pathogens causing post-neurosurgical bacterial meningitis; Gram-negative bacterial meningitis are more likely to occur in autumn and within the first month after surgery. Acinetobacter baumannii has a high resistance rate to carbapenem antibiotics, which should be taken seriously.

Construction and Optimization of Nonclassical Isoprenoid Biosynthetic Pathways in Yeast Peroxisomes for (+)-Valencene Production

Isoprenoids are a kind of natural product with various activities, but their plant extraction suffers low concentration. The rapid development of synthetic biology offers a sustainable route for supply of high-value-added natural products by engineering microorganisms. However, the complexity of cellular metabolism makes engineering endogenous isoprenoid biosynthetic pathways with metabolic interaction difficult. Here, for the first time, we constructed and optimized three types of isoprenoid pathways (the Haloarchaea-type, Thermoplasma-type, and isoprenoid alcohol pathway) in yeast peroxisomes for the synthesis of sesquiterpene (+)-valencene. In yeast, the Haloarchaea-type MVA pathway is more effective than the classical MVA pathway. MVK and IPK were determined to be the rate-limiting steps of the Haloarchaea-type MVA pathway, and the production of 869 mg/L (+)-valencene under fed-batch fermentation in shake flasks was realized. This work expands isoprenoid synthesis in eukaryotes and provides a more efficient pathway for isoprenoid synthesis.

Efficient Spin-to-Charge Conversion via Altermagnetic Spin Splitting Effect in Antiferromagnet RuO_{2}

The relativistic spin Hall effect and inverse spin Hall effect enable the efficient generation and detection of spin current. Recently, a nonrelativistic altermagnetic spin splitting effect (ASSE) has been theoretically and experimentally reported to generate time-reversal-odd spin current with controllable spin polarization in antiferromagnet RuO_{2}. The inverse effect, electrical detection of spin current via ASSE, still remains elusive. Here we show the spin-to-charge conversion stemming from ASSE in RuO_{2} by the spin Seebeck effect measurements. Unconventionally, the spin Seebeck voltage can be detected even when the injected spin current is polarized along the directions of either the voltage channel or the thermal gradient, indicating the successful conversion of x- and z-spin polarizations into the charge current. The crystal axes-dependent conversion efficiency further demonstrates that the nontrivial spin-to-charge conversion in RuO_{2} is ascribed to ASSE, which is distinct from the magnetic or antiferromagnetic inverse spin Hall effects. Our finding not only advances the emerging research landscape of altermagnetism, but also provides a promising pathway for the spin detection.

[A prospective study on the safety and efficacy of excimer laser coronary angioplasty for the treatment of degenerated great saphenous vein graft]

Objective: To explore the safety and efficacy of excimer laser coronary angioplasty (ELCA) for the treatment of degenerated great saphenous vein graft (SVG). Methods: This is a single-center, prospective, single-arm study. Patients, who were admitted to the Geriatric Cardiovascular Center of Beijing Anzhen Hospital from January 2022 to June 2022, were consecutively enrolled. Inclusion criteria were recurrent chest pain after coronary artery bypass surgery (CABG), and coronary angiography confirmed that the SVG stenosis was more than 70% but not completely occluded, and interventional treatment for SVG lesions was planned. Before balloon dilation and stent placement, ELCA was used to pretreat the lesions. Optical coherence tomography (OCT) examination was performed and postoperative index of microcirculation resistance (IMR) were assessed after stent implantation. The technique success rate and operation success rate were calculated. The technique success was defined as the successful passage of the ELCA system through the lesion. Operation success was defined as the successful placement of a stent at the lesion. The primary evaluation index of the study was IMR immediately after PCI. Secondary evaluation indexes included thrombolysis in myocardial infarction (TIMI) flow grade, corrected TIMI frame count (cTFC), minimal stent area and stent expansion measured by OCT after PCI, and procedural complications (Ⅳa myocardial infarction, no reflow, perforation). Results: A total of 19 patients aged (66.0±5.6) years were enrolled, including 18 males (94.7%). The age of SVG was 8 (6, 11) years. The length of the lesions was greater than 20 mm, and they were all SVG body lesions. The median stenosis degree was 95% (80%, 99%), and the length of the implanted stent was (41.7±16.3)mm. The operation time was 119 (101, 166) minutes, and the cumulative dose was 2 089 (1 378, 3 011)mGy. The diameter of the laser catheter was 1.4 mm, the maximum energy was 60 mJ, and the maximum frequency was 40 Hz. The technique success and the operation success rate were both 100% (19/19). The IMR after stent implantation was 29.22±5.95. The TIMI flow grade of patients after ELCA and stent implantation was significantly improved (all P>0.05), and the TIMI flow grade of all patients after stent implantation was Grade Ⅲ. The cTFC decreased significantly after ELCA (33.2±7.8) and after stent placement (22.8±7.1) than preoperative level (49.7±13.0) (both P<0.001). The minimum stent area was (5.53±1.36)mm², and the stent expansion rate was (90.0±4.3)%. Perforation, no reflow, type Ⅳa myocardial infarction and other complications were not observed. However, postoperative high-sensitivity troponin level was significantly increased ((67.937±33.839)ng/L vs. (5.316±3.105)ng/L, P<0.001). Conclusion: ELCA is safe and effective in the treatment of SVG lesions and could improve microcirculation and ensure full expansion of stent.

[Safety and efficacy of the early administration of levosimendan in patients with acute non-ST-segment elevation myocardial infarction and elevated NT-proBNP levels: An Early Management Strategy of Acute Heart Failure (EMS-AHF)]

Objectives: To investigated the safety and efficacy of treating patients with acute non-ST-segment elevation myocardial infarction (NSTEMI) and elevated levels of N-terminal pro-hormone B-type natriuretic peptide (NT-proBNP) with levosimendan within 24 hours of first medical contact (FMC). Methods: This multicenter, open-label, block-randomized controlled trial (NCT03189901) investigated the safety and efficacy of levosimendan as an early management strategy of acute heart failure (EMS-AHF) for patients with NSTEMI and high NT-proBNP levels. This study included 255 patients with NSTEMI and elevated NT-proBNP levels, including 142 males and 113 females with a median age of 65 (58-70) years, and were admitted in the emergency or outpatient departments at 14 medical centers in China between October 2017 and October 2021. The patients were randomly divided into a levosimendan group (n=129) and a control group (n=126). The primary outcome measure was NT-proBNP levels on day 3 of treatment and changes in the NT-proBNP levels from baseline on day 5 after randomization. The secondary outcome measures included the proportion of patients with more than 30% reduction in NT-proBNP levels from baseline, major adverse cardiovascular events (MACE) during hospitalization and at 6 months after hospitalization, safety during the treatment, and health economics indices. The measurement data parameters between groups were compared using the t-test or the non-parametric test. The count data parameters were compared between groups using the χ² test. Results: On day 3, the NT-proBNP levels in the levosimendan group were lower than the control group but were statistically insignificant [866 (455, 1 960) vs. 1 118 (459, 2 417) ng/L, Z=-1.25,P=0.21]. However, on day 5, changes in the NT-proBNP levels from baseline in the levosimendan group were significantly higher than the control group [67.6% (33.8%,82.5%)vs.54.8% (7.3%,77.9%), Z=-2.14, P=0.03]. There were no significant differences in the proportion of patients with more than 30% reduction in the NT-proBNP levels on day 5 between the levosimendan and the control groups [77.5% (100/129) vs. 69.0% (87/126), χ²=2.34, P=0.13]. Furthermore, incidences of MACE did not show any significant differences between the two groups during hospitalization [4.7% (6/129) vs. 7.1% (9/126), χ²=0.72, P=0.40] and at 6 months [14.7% (19/129) vs. 12.7% (16/126), χ²=0.22, P=0.64]. Four cardiac deaths were reported in the control group during hospitalization [0 (0/129) vs. 3.2% (4/126), P=0.06]. However, 6-month survival rates were comparable between the two groups (log-rank test, P=0.18). Moreover, adverse events or serious adverse events such as shock, ventricular fibrillation, and ventricular tachycardia were not reported in both the groups during levosimendan treatment (days 0-1). The total cost of hospitalization [34 591.00(15 527.46,59 324.80) vs. 37 144.65(16 066.90,63 919.00)yuan, Z=-0.26, P=0.80] and the total length of hospitalization [9 (8, 12) vs. 10 (7, 13) days, Z=0.72, P=0.72] were lower for patients in the levosimendan group compared to those in the control group, but did not show statistically significant differences. Conclusions: Early administration of levosimendan reduced NT-proBNP levels in NSTEMI patients with elevated NT-proBNP and did not increase the total cost and length of hospitalization, but did not significantly improve MACE during hospitalization or at 6 months.

Peroxisomal metabolic coupling improves fatty alcohol production from sole methanol in yeast

Methanol is an ideal feedstock for chemical and biological manufacturing. Constructing an efficient cell factory is essential for producing complex compounds through methanol biotransformation, in which coordinating methanol use and product synthesis is often necessary. In methylotrophic yeast, methanol utilization mainly occurs in peroxisomes, which creates challenges in driving the metabolic flux toward product biosynthesis. Here, we observed that constructing the cytosolic biosynthesis pathway resulted in compromised fatty alcohol production in the methylotrophic yeast Ogataea polymorpha. Alternatively, peroxisomal coupling of fatty alcohol biosynthesis and methanol utilization significantly improved fatty alcohol production by 3.9-fold. Enhancing the supply of precursor fatty acyl-CoA and cofactor NADPH in the peroxisomes by global metabolic rewiring further improved fatty alcohol production by 2.5-fold and produced 3.6 g/L fatty alcohols from methanol under fed-batch fermentation. We demonstrated that peroxisome compartmentalization is helpful for coupling methanol utilization and product synthesis, and with this approach, constructing efficient microbial cell factories for methanol biotransformation is feasible.

[Comparison of leadless pacemaker and conventional pacemaker for quality of life improvement in patients with bradyarrhythmias]

Objective: To compare the improvement in quality of life (QoL) after implantation of leadless pacemakers (L-PM) with that of conventional pacemakers (C-PM) in patients with slow-onset arrhythmias. Methods: A total of 112 patients who received pacemaker implantation for the first time at Beijing Anzhen Hospital from January 2020 to July 2021 were selected, including 50 leadless pacemakers (L-PM) and 62 conventional pacemakers (C-PM). Clinical baseline data were collected, pacemaker-related complications and SF-36 scores were recorded and followed up at 1, 3, and 12 months post-operatively; SF-36 questionnaires and additional questionnaires were completed to compare the quality of life of the 2 groups; and factors associated with the change in QoL from baseline to 1, 3 and 12 months post-operatively were analyzed using multiple linear regression models. Results: The age of the 112 patients was (70.3±10.5) years, and 69 patients (61.6%) were male. The age of patients with L-PM and C-PM was (75.8±8.5) years and (67.5±10.4) years, respectively (P=0.004). In the L-PM group, 50 patients completed 1-, 3-, and 12-month follow-up. In the C-PM group, 62 patients completed the 1-month and 3-month follow-up, and 60 completed the 12-month follow-up. The C-PM group had a higher incidence of discomfort in the surgical area, impact of daily activities for the discomfort in the surgical area, and concern about heart or overall condition than the L-PM group on the additional questionnaire (all P values<0.05). After adjusting for age and SF-36 scores at baseline, at 12^th month of follow-up, patients implanted with C-PM had lower values for quality of life PF, RP, SF, RE, and MH scores compared to patients implanted with L-PM, with beta values (95%CI) of -24.500 (-30.010--18.981), -27.118 (-32.997--21.239), -8.085 (-12.536--3.633), -4.839 (-9.437--0.241), -12.430 (-18.558--6.301), respectively (all P values<0.05). Conclusions: L-PM is associated with better QoL in slow arrhythmias patients, and patients who received L-PM reported less activity limitations due to surgical discomfort and less emotional distress.

Auxotrophs compromise cell growth and fatty acid production in Saccharomyces cerevisiae

Auxotrophic marker genes have been widely used for genetic engineering in yeast. However, the effects of amino acids or nucleotides deficiency in auxotrophic strains on cell growth and product synthesis were rarely reported. In this study, a total of eight auxotrophic strains of Saccharomyces cerevisiae with single knockout of selection markers were obtained. Cell growth and free fatty acid (FFA) production of these auxotrophic strains were evaluated with supplementation of different concentrations of amino acids or nucleotides. Generally, except ade2Δ mutants, most auxotrophic strains showed decreased cell growth and FFA production, which could be recovered by adding higher concentrations of supplements. LEU2 deletion (leu2Δ) damaged both cell growth and FFA production even with supplementation of 1000 mg L^-1 leucine. This study shows that growth and product biosynthesis of auxotrophs could be limited by insufficient supplementation of amino acids or nucleotides, and provides guidance on supplementation of these nutrients during fermentation to maximize cell growth and product biosynthesis.

Skeleton-Reorganizing Coupling Reactions of Cycloheptatriene and Cycloalkenones with Amines

Skeletal reorganization reactions have emerged as an intriguing tool for converting readily available compounds into complicated molecules inaccessible by traditional methods. Herein, we report a unique skeleton-reorganizing coupling reaction of cycloheptatriene and cycloalkenones with amines. In the presence of Rh/acid catalysis, cycloheptatriene can selectively couple with anilines to deliver fused 1,2-dihydroquinoline products. Mechanistic studies indicate that the retro-Mannich type ring-opening and subsequent intramolecular Povarov reaction account for the ring reorganization. Our mechanistic studies also revealed that skeleton-reorganizing amination between anilines and cycloalkenones can be achieved with acid. The synthetic utilization of this skeleton-reorganizing coupling reaction was showcased with a gram-scale reaction, synthetic derivatizations, and the late-stage modification of commercial drugs.

Engineering yeast for high-level production of diterpenoid sclareol

The diterpenoid sclareol is an industrially important precursor for alternative sustainable supply of ambergris. However, its current production from plant extraction is neither economical nor environmental-friendly, since it requires laborious and cost-intensive purification procedures and plants cultivation is susceptible to environmental factors. Engineering cell factories for bio-manufacturing can enable sustainable production of natural products. However, stringent metabolic regulation poses challenges to rewire cellular metabolism for overproduction of compounds of interest. Here we used a modular approach to globally rewire the cellular metabolism for improving sclareol production to 11.4 g/L in budding yeast Saccharomyces cerevisiae, the highest reported diterpenoid titer in microbes. Metabolic flux analysis showed that modular balanced metabolism drove the metabolic flux toward the biosynthesis of targeted molecules, and transcriptomic analysis revealed that the expression of central metabolism genes was shaped for a new balanced metabolism, which laid a foundation in extensive metabolic engineering of other microbial species for sustainable bio-production.

[Role of preoperative ultrasound-guided inferior parathyroid gland localization and new classification to assist intraoperative search and protection of parathyroid glands]

Objective: To investigate the role and significance of ultrasound-guided inferior parathyroid gland (IPTG) localization in searching and protecting parathyroid glands before thyroid surgery. Methods: A randomized controlled trial study was conducted. A total of 306 patients (433 cases of lateral parathyroidectomy) who underwent primary thyroidectomy and central lymph node dissection in Beijing Tongren Hosipital from March to October 2021 were enrolled. In order to locate IPTG more quickly and effectively, new IPTG classification and the definition of quadrant position were carried out. The patients were divided into the study group (n=228) and the control group (n=205). The study group underwent ultrasound-guided IPTG examination before operation and measured the distance between the IPTG and the lower pole of the thyroid and the midline of the trachea. During the operation, the IPTG was found and protected depending on the localization. The control group did not use any auxiliary preoperative positioning method. The distribution ratio of IPTG and the coincidence rate between intraoperative validation and ultrasound localization were calculated. Results: There were 306 patients enrolled in the final analysis (95 males and 211 females), with a median age of 41 years old (18-70). Type Ⅱ and Ⅲ IPTG accounted for 77.2% (176/228) of the total cases. The total coincidence rate ranged from 72.8% to 79.4% in different IPTG groups. Type Ⅲ and quadrant 2 IPTG had the highest coincidence rate [92.4% (73/79) and 92.9% (79/85), respectively]. The study group had better in situ retention rate [82.0% (187/228) vs 73.2% (150/205), χ²=4.896, P=0.027] and less implantation rate [8.8% (20/228) vs 16.1% (33/205), χ²=5.393, P=0.020] than those of the control group. The in situ retention rate were better in type Ⅲ IPTG group, compared with those of the control group [94.9% (74/78) vs 77.4% (48/62), χ²=7.898, P=0.005]. There was no permanent hypoparathyroidism in two groups and the temporary hypoparathyroidism rate was 32.0% (24/75) and 34.6% (18/52), respectively (χ²=0.095, P=0.758). Conclusion: Ultrasound-guided IPTG localization examination has important implications for searching and protecting IPTG during operation, which can significantly increase in situ retention rate of IPTG and decrease the implantation rate.

Overproduction of 3-hydroxypropionate in a super yeast chassis

3-Hydroxypropionate (3-HP) is a platform chemical for production of acrylic acid, acrylamide and biodegradable polymers. Several microbial cell factories have been constructed for production of 3-HP from malonyl-CoA by using a malonyl-CoA reductase, which however suffer from inadequate supply of precursor and cofactor. Here 3-HP biosynthesis was optimized in a super yeast chassis with sufficient supply of precursor malonyl-CoA and cofactor NADPH, which had a 3-fold higher 3-HP (1.4 g/L) than that of wild-type background. The instability of the engineered strain was observed in fed-batch fermentation due to the plasmid loss, which may be caused by the toxic intermediate malonate semialdehyde. Genome integration of MCR-C encoding C-terminal of MCR enabled stable gene expression and much higher 3-HP production of 4.4 g/L under batch fermentation and 56.5 g/L under fed-batch fermentation with a yield of 0.31 g/g glucose. This was the highest 3-HP production reported from glucose in engineered microbes.

[Analysis of HIV transmission hotspots and characteristics of cross-regional transmission in Guangxi Zhuang Autonomous Region based on molecular network]

Objective: To analyze HIV transmission hotspots and characteristics of cross-regional transmission in Guangxi Zhuang autonomous region (Guangxi) based on the molecular network analysis, and provide evidence for optimization of precise AIDS prevention and control strategies. Methods: A total of 5 996 HIV pol sequences sampled from Guangxi between 1997 and 2020 were analyzed together with 165 534 published HIV pol sequences sampled from other regions. HIV-TRACE was used to construct molecular network in a pairwise genetic distance threshold of 0.5%. Results: The proportion of HIV sequences entering the molecular network of HIV transmission hotspots in Guangxi was 31.5% (1 886/5 996). In the molecular network of HIV cross-regional transmission, the links within Guangxi accounted for 51.6% (2 613/5 062), the links between Guangxi and other provinces in China accounted for 48.0% (2 430/5 062), and the links between Guangxi and other countries accounted for 0.4% (19/5 062). The main regions which had cross-regional linked with Guangxi were Guangdong (49.5%, 1 212/2 449), Beijing (17.5%, 430/2 449), Shanghai (6.9%, 168/2 449), Sichuan (5.7%, 140/2 449), Yunnan (4.2%, 102/2 449), Shaanxi (3.8%, 93/2 449), Zhejiang (2.8%, 69/2 449), Hainan (2.0%, 49/2 449), Anhui (1.5%, 37/2 449), Jiangsu (1.3%, 33/2 449), and other regions (each one <1.0%), respectively. The risk factors of entering the molecular network of HIV transmission hotspots in Guangxi included being aged ≥50 years (compared with being aged 25-49 years, aOR=1.68,95%CI:1.46-1.95), males (compared with females, aOR=1.21,95%CI:1.05-1.40), being single (compared with being married, aOR=1.18,95%CI:1.00-1.39), having education level of high school or above (compared with having education level of junior high school or below, aOR=1.21,95%CI:1.04-1.42), acquired HIV through homosexual intercourse (compared with acquired with HIV through heterosexual intercourse, aOR=1.77, 95%CI:1.48-2.12). The risk factors of cross-regional transmission included males (compared with females, aOR=1.74,95%CI:1.13-2.75), having education level of high school or above (compared with having education level of junior high school or below, aOR=1.96,95%CI:1.43-2.69), being freelancer/unemployed/retired (compared with being farmers, aOR=1.50,95%CI:1.07-2.11), acquired HIV through homosexual intercourse (compared with acquired with HIV through heterosexual intercourse, aOR=3.28,95%CI:2.30-4.72). Conclusion: There are HIV transmission hotspots in Guangxi. Guangxi and other provinces in China form a complex cross-regional transmission network. Future studies should carry out social network surveys in high-risk populations inferred from the molecular network analysis for the timely identification of hidden transmission chains and reduction of the second-generation transmission of HIV.

Fusing an exonuclease with Cas9 enhances homologous recombination in Pichia pastoris

BACKGROUND

The methylotrophic yeast Pichia pastoris is considered as an ideal host for the production of recombinant proteins and chemicals. However, low homologous recombination (HR) efficiency hinders its precise and extensive genetic manipulation. To enhance the homology-directed repair over non-homologous end joining (NHEJ), we expressed five exonucleases that were fused with the Cas9 for enhancing end resection of double strand breaks (DSBs) of DNA cuts.

RESULTS

The endogenous exonuclease Mre11 and Exo1 showed the highest positive rates in seamless deletion of FAA1, and fusing the MRE11 to the C-terminal of CAS9 had the highest positive rate and relatively high number of clones. We observed that expression of CAS9-MRE11 significantly improved positive rates when simultaneously seamless deletion of double genes (from 76.7 to 86.7%) and three genes (from 10.8 to 16.7%) when overexpressing RAD52. Furthermore, MRE11 overexpression significantly improved the genomic integration of multi-fragments with higher positive rate and clone number.

CONCLUSIONS

Fusion expression of the endogenous exonuclease Mre11 with Cas9 enhances homologous recombination efficiency in P. pastoris. The strategy described here should facilitate the metabolic engineering of P. pastoris toward high-level production of value-added compounds.

Comparative proteomics analysis of Pichia pastoris cultivating in glucose and methanol

The methylotrophic yeast Pichia pastoris (syn. Komagataella phaffii) has been extensively engineered for protein production, and is attracting attention as a chassis cell for methanol biotransformation toward production of small molecules. However, the relatively unclear methanol metabolism hampers the metabolic rewiring to improve the biosynthetic efficiency. We here performed a label-free quantitative proteomic analysis of Pichia pastoris when cultivated in minimal media containing methanol and glucose, respectively. There were 243, 158 up-regulated proteins and 244, 304 down-regulated proteins in log and stationary phase, respectively, when cultivated in methanol medium compared with that of glucose medium. Peroxisome enrichment further improved the characterization of more differentially expressed proteins (481 proteins in log phase and 524 proteins in stationary phase). We demonstrated the transaldolase isoenzyme (Tal2, Protein ID: C4R244) was highly up-regulated in methanol medium cultivation, which plays an important role in methanol utilization. Our work provides important information for understanding methanol metabolism in methyltrophic yeast and will help to engineer methanol biotransformation in P. pastoris.

Expanding the neutral sites for integrated gene expression in Saccharomyces cerevisiae

Construction of efficient microbial cell factories always requires assembling biosynthetic pathways and rewiring cellular metabolism with overexpression of multiple genes. Genomic integration is considered to be helpful for stable gene expression in compared with the episomal plasmids. However, the limited availability of suitable loci hinders the extensive metabolic engineering. We here characterized 30 neutral sites in Saccharomyces cerevisiae genome that did not affect cellular fitness by using expression cassettes of green fluorescent protein (eGFP) and fatty acyl-CoA reductase (MaFAR1) with the aid of efficient CRISPR-Cas9 technique. We found that integration of gene expression cassettes to different genome loci resulted a varied GFP signal and fatty alcohol production, which showed that genomic loci could be used for tuning gene expression. The characterized set of neutral sites should be helpful for extensively metabolic engineering of S. cerevisiae for chemical production and other purposes.

Production of free fatty acids from various carbon sources by Ogataea polymorpha

Energy shortage and environmental concern urgently require establishing the feasible bio-refinery process from various feedstocks. The methylotrophic yeast Ogataea polymorpha is thermo-tolerant and can utilize various carbon sources, such as glucose, xylose and methanol, which makes it a promising host for bio-manufacturing. Here, we explored the capacity of O. polymorpha for overproduction of free fatty acids (FFAs) from multiple substrates. The engineered yeast produced 674 mg/L FFA from 20 g/L glucose in shake flask and could sequentially utilize the mixture of glucose and xylose. However, the FFA producing strain failed to survive in sole methanol and supplementing co-substrate xylose promoted methanol metabolism. A synergistic utilization of xylose and methanol was observed in the FFA producing strain. Finally, a mixture of glucose, xylose and methanol was evaluated for FFA production (1.2 g/L). This study showed that O. polymorpha is an ideal host for chemical production from various carbon sources.

Rescuing yeast from cell death enables overproduction of fatty acids from sole methanol

Methanol is an ideal feedstock for biomanufacturing that can be beneficial for global carbon neutrality; however, the toxicity of methanol limits the efficiency of methanol metabolism toward biochemical production. We here show that engineering production of free fatty acids from sole methanol results in cell death with decreased cellular levels of phospholipids in the methylotrophic yeast Ogataea polymorpha, and cell growth is restored by adaptive laboratory evolution. Whole-genome sequencing of the adapted strains reveals that inactivation of LPL1 (encoding a putative lipase) and IZH3 (encoding a membrane protein related to zinc metabolism) preserve cell survival by restoring phospholipid metabolism. Engineering the pentose phosphate pathway and gluconeogenesis enables high-level production of free fatty acid (15.9 g l^-1) from sole methanol. Preventing methanol-associated toxicity underscores the link between lipid metabolism and methanol tolerance, which should contribute to enhancing methanol-based biomanufacturing.

Global Metabolic Rewiring of Yeast Enables Overproduction of Sesquiterpene (+)-Valencene

(+)-Valencene is a bioactive sesquiterpene that can be used for flavoring and fragrances, and microbial production provides an alternative sustainable access. However, the complexity of cellular metabolism makes it challenging for its high-level production. Here, we report the global rewiring cellular metabolism for de novo production of (+)-valencene in yeast Saccharomyces cerevisiae by engineering central metabolism, mevalonate pathway, and sesquiterpenoid synthase. In particular, we show that metabolic transformation can help accelerate the strain construction process and multiple copy expression of sesquiterpenoid synthase is essential for boosting the metabolic flux for product synthesis with enhanced supply of precursors. The engineered strain produced 1.2 g/L (+)-valencene under fed-batch fermentation in shake flasks, which was increased by 549-fold and demonstrated great potential of the yeast cell factory for (+)-valencene production.

Microbial synthesis of long-chain α-alkenes from methanol by engineering Pichia pastoris

α-Alkenes (terminal alkenes) are important fuel and platform chemicals that are mainly produced from petroleum. Microbial synthesis might provide a sustainable approach for α-alkenes. In this work, we engineered the methylotrophic yeast Pichia pastoris to produce long-chain (C15:1, C17:1 and C17:2) α-alkenes via a decarboxylation of fatty acids. Combinatorial engineering, including enzyme selection, expression optimization and peroxisomal compartmentalization, enabled the production of 1.6 mg/L α-alkenes from sole methanol. This study represents the first case of α-alkene biosynthesis from methanol and also provides a reference for the construction of methanol microbial cell factories of other high-value chemicals.

Observation of Spin Splitting Torque in a Collinear Antiferromagnet RuO_{2}

Current-induced spin torques provide efficient data writing approaches for magnetic memories. Recently, the spin splitting torque (SST) was theoretically predicted, which combines advantages of conventional spin transfer torque (STT) and spin-orbit torque (SOT) as well as enables controllable spin polarization. Here we provide the experimental evidence of SST in collinear antiferromagnet RuO_{2} films. The spin current direction is found to be correlated to the crystal orientation of RuO_{2} and the spin polarization direction is dependent on (parallel to) the Néel vector. These features are quite characteristic for the predicted SST. Our finding not only presents a new member for the spin torques besides traditional STT and SOT, but also proposes a promising spin source RuO_{2} for spintronics.

[Production of fatty acids by engineered Ogataea polymorpha]

Fatty acids (FA) are widely used as feed stocks for the production of cosmetics, personal hygiene products, lubricants and biofuels. Ogataea polymorpha is considered as an ideal chassis for bio-manufacturing, due to its outstanding characteristics such as methylotroph, thermal-tolerance and wide substrate spectrum. In this study, we harnessed O. polymorpha for overproduction of fatty acids by engineering its fatty acid metabolism and optimizing the fermentation process. The engineered strain produced 1.86 g/L FAs under the optimized shake-flask conditions (37℃, pH 6.4, a C/N ratio of 120 and an OD₆₀₀ of seed culture of 6-8). The fed-batch fermentation process was further optimized by using a dissolved oxygen (DO) control strategy. The C/N ratio of initial medium was 17.5, and the glucose medium with a C/N ratio of 120 was fed when the DO was higher than 30%. This operation resulted in a titer of 18.0 g/L FA, indicating the potential of using O. polymorpha as an efficient cell factory for the production of FA.

Characterizing and engineering promoters for metabolic engineering of Ogataea polymorpha

Bio-manufacturing via microbial cell factory requires large promoter library for fine-tuned metabolic engineering. Ogataea polymorpha, one of the methylotrophic yeasts, possesses advantages in broad substrate spectrum, thermal-tolerance, and capacity to achieve high-density fermentation. However, a limited number of available promoters hinders the engineering of O. polymorpha for bio-productions. Here, we systematically characterized native promoters in O. polymorpha by both GFP fluorescence and fatty alcohol biosynthesis. Ten constitutive promoters (P_PDH, P_PYK, P_FBA, P_PGM, P_GLK, P_TRI, P_GPI, P_ADH1, P_TEF1 and P_GCW14) were obtained with the activity range of 13%–130% of the common promoter P_GAP (the promoter of glyceraldehyde-3-phosphate dehydrogenase), among which P_PDH and P_GCW14 were further verified by biosynthesis of fatty alcohol. Furthermore, the inducible promoters, including ethanol-induced P_ICL1, rhamnose-induced P_LRA3 and P_LRA4, and a bidirectional promoter (P_Mal-P_Per) that is strongly induced by sucrose, further expanded the promoter toolbox in O. polymorpha. Finally, a series of hybrid promoters were constructed via engineering upstream activation sequence (UAS), which increased the activity of native promoter P_LRA3 by 4.7–10.4 times without obvious leakage expression. Therefore, this study provided a group of constitutive, inducible, and hybrid promoters for metabolic engineering of O. polymorpha, and also a feasible strategy for rationally regulating the promoter strength.

Characterizing methanol metabolism-related promoters for metabolic engineering of Ogataea polymorpha

Promoters play an important role in regulating gene expression, and construction of microbial cell factories requires multiple promoters for balancing the metabolic pathways. However, there are only a limited number of characterized promoters for gene expression in the methylotrophic yeast Ogataea polymorpha, which hampers the extensive harnessing of this important yeast toward a cell factory. Here we characterized the promoters of methanol utilization pathway, precursor supply pathway, and reactive oxygen species (ROS) defense system, by using a green fluorescence protein variant (GFP_UV) as a quantification signal. Finally, the characterized promoters were used for tuning a fatty alcohol biosynthetic pathway in O. polymorpha and realized fatty alcohol production from methanol. This promoter box should be helpful for gene expression and pathway optimization in the methylotrophic yeast O. polymorpha. KEY POINTS : • 22 promoters related to methanol metabolism were characterized in O. polymorpha. • Promoter truncation resulted shorter and compact promoters. • Promoters with various strengths were used for regulating a fatty alcohol biosynthesis from methanol.

Recombination machinery engineering facilitates metabolic engineering of the industrial yeast Pichia pastoris

The industrial yeast Pichia pastoris has been harnessed extensively for production of proteins, and it is attracting attention as a chassis cell factory for production of chemicals. However, the lack of synthetic biology tools makes it challenging in rewiring P. pastoris metabolism. We here extensively engineered the recombination machinery by establishing a CRISPR-Cas9 based genome editing platform, which improved the homologous recombination (HR) efficiency by more than 54 times, in particular, enhanced the simultaneously assembly of multiple fragments by 13.5 times. We also found that the key HR-relating gene RAD52 of P. pastoris was largely repressed in compared to that of Saccharomyces cerevisiae. This gene editing system enabled efficient seamless gene disruption, genome integration and multiple gene assembly with positive rates of 68–90%. With this efficient genome editing platform, we characterized 46 potential genome integration sites and 18 promoters at different growth conditions. This library of neutral sites and promoters enabled two-factorial regulation of gene expression and metabolic pathways and resulted in a 30-fold range of fatty alcohol production (12.6–380 mg/l). The expanding genetic toolbox will facilitate extensive rewiring of P. pastoris for chemical production, and also shed light on engineering of other non-conventional yeasts.

Screening neutral sites for metabolic engineering of methylotrophic yeast Ogataea polymorpha

Methylotrophic yeast Ogataea polymorpha is capable to utilize multiple carbon feedstocks especially methanol as sole carbon source and energy, making it an ideal host for bio-manufacturing. However, the lack of gene integration sites limits its systems metabolic engineering, in particular construction of genome-integrated pathway. We here screened the genomic neutral sites for gene integration without affecting cellular fitness, by genomic integration of an enhanced green fluorescent protein (eGFP) gene via CRISPR-Cas9 technique. After profiling the growth and fluorescent intensity in various media, 17 genome positions were finally identified as potential neutral sites. Finally, integration of fatty alcohol synthetic pathway genes into neutral sites NS2 and NS3, enabled the production of 4.5 mg/L fatty alcohols, indicating that these neutral sites can be used for streamline metabolic engineering in O. polymorpha. We can anticipate that the neutral sites screening method described here can be easily adopted to other eukaryotes.

[Advances in metabolic engineering of methylotrophic yeasts]

Methylotrophic yeasts are considered as promising cell factories for bio-manufacturing due to their several advantages such as tolerance to low pH and high temperature. In particular, their methanol utilization ability may help to establish a methanol biotransformation process, which will expand the substrate resource for bio-refinery and the product portfolio from methanol. This review summarize current progress on engineering methylotrophic yeasts for production of proteins and chemicals, and compare the strengths and weaknesses with the model yeast Saccharomyces cerevisiae. The challenges and possible solutions in metabolic engineering of methylotrophic yeasts are also discussed. With the developing efficient genetic tools and systems biology, the methylotrophic yeasts should play more important roles in future green bio-manufacturing.

[The role of time-series propagation map and activity path of confirmed cases in the analysis and determination of COVID-19 epidemic]

Objective: The time sequence transmission map and the cases travel track were used to explain the chain of transmission, describe the characteristics of transmission and analyze the mode of epidemic of novel coronavirus pneumonia, so as to provide evidence for the relevant government departments to carry out epidemic prevention and control. Methods: The time sequence transmission map and the cases travel track table were drawn, according to the time of incidence, age, sex, number of close contacts and their interrelations. Results: At the end of February 10, 2020, 63 COVID-19 cases were reported in the research area. Among them, 57 cases were confirmed (1 deaths) and 6 cases were asymptomatic, 57 cases were imported cases (90.48%), 36 cases were reported by cluster epidemic (57.14%) among friends and relatives. Cases have been spread to the fourth generation. Conclusion: The time sequence transmission map and the cases travel track showed that, in the research area, the epidemic situation of COVID-19 was mainly caused by imported case, and the clustering transmission was the major spread model. The time sequence transmission map and the cases travel track are worth popularizing in the prevention and control of major infectious diseases.

Large Isospin Asymmetry in ^{22}Si/^{22}O Mirror Gamow-Teller Transitions Reveals the Halo Structure of ^{22}Al

β-delayed one-proton emissions of ^{22}Si, the lightest nucleus with an isospin projection T_{z}=-3, are studied with a silicon array surrounded by high-purity germanium detectors. Properties of β-decay branches and the reduced transition probabilities for the transitions to the low-lying states of ^{22}Al are determined. Compared to the mirror β decay of ^{22}O, the largest value of mirror asymmetry in low-lying states by far, with δ=209(96), is found in the transition to the first 1^{+} excited state. Shell-model calculation with isospin-nonconserving forces, including the T=1, J=2, 3 interaction related to the s_{1/2} orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the s_{1/2} orbit, can reproduce the observed data well and consistently explain the observation that a large δ value occurs for the first but not for the second 1^{+} excited state of ^{22}Al. Our results, while supporting the proton-halo structure in ^{22}Al, might provide another means to identify halo nuclei.

Construction of SNP-STR Multiplex Amplification System with Genetic Markers and Its Forensic Application

Abstract

Objective To select and develop a SNP-STR multiplex amplification system with genetic markers compatible with current STR databases. To understand its genetic polymorphisms in Sichuan Han population and its application value in DNA mixture analysis. Methods Based on the STR genetic markers in commercial kits, SNPs adjacent to these STR markers were selected to be SNP-STR genetic markers. A SNP-STR multiplex amplification system with genetic markers based on allele-specific amplification was constructed using allele-specific amplification primers. The genetic polymorphism of the system in the Sichuan Han population was investigated and the efficiency of systems with different numbers of loci to detect the two individual DNA mixture samples was evaluated. Results An allele-specific multiplex amplification system constituted of 13 SNP-STR genetic markers was selected and constructed. In Sichuan Han population, the heterozygosity of each locus ranged from 0.76 to 0.88, and the combined discrimination power reached 0.999 999 999 999 999 968. In the analysis of the two individual DNA mixture samples： for single-locus amplification, the genotype of the minor components can still be detected when the mixture ratio reaches 1 000∶1; for multiple loci multiplex amplification, the maximum mixture ratio can reach 500∶1. As the number of loci in the system increased, the detection efficiency of the minor components in the DNA mixture decreased. Conclusion SNP-STR genetic markers have a higher polymorphism than STR. The multiplex amplification system made of SNP-STR genetic markers has a better analysis efficiency for mixed samples than traditional STR multiplex amplification system.

[Initial implantation experience and short-term follow-up results of implanting leadless intracardiac transcatheter pacing system]

Objective: To explore the utility and safety of leadless intracardiac transcatheter pacing system. Methods: The study was a prospective observational study. Patients underwent Micra transcatheter pacing system in Beijing Anzhen hospital from December 2019 to January 2020 were enrolled. The baseline characteristics, platelet count, hemoglobin, anticoagulation and/or antiplatelet therapy, mean procedural time, average fluoroscopy time, number of deployment and electrical parameters (threshold, R-wave amplitude, impedance) were recorded. Ultrasonography of bilateral femoral and iliac veins was performed in all patients. Patients were followed including access site complication, adverse event and device evaluation at implant, hospital discharge, 1 and 3 months post-implant. R-wave≥5 mV, impedance between 400 and 1 500 Ω and threshold increase≤1.5 V than implant is considered a stable parameter. Femoral access site complications included hematoma, hemorrhage, pseudoaneurysm, and arteriovenous fistula. Adverse events included dislodgement, cardiac effusion/perforation and infection. Left ventricular end diastolic diameter and ejection fraction before and at 1 month after implant were reported. Results: Five patients were enrolled and pacemaker implantation was successful in all 5 patients. Patients were all males and the average age was (78.4±8.4) years. 2 patients received aspirin and clopidogrel therapy, 1 patient suffered from anemia and thrombocytopenia occurred in 1 patient. No stenosis, occlusion and vascular malformation of bilateral femoral and iliac veins was observed. The mean implant time was (39.6±1.7) minutes. The average fluoroscopy time was (9.2±1.3) minutes and the number of deployment was (1.40±0.55). Electrical parameters(threshold, R-Wave amplitude and impedance) were as follows: (0.40±0.10) V/0.24 ms, (10.80±3.72) mV and (822.00±162.23) Ω at implant; (0.45±0.07) V/0.24 ms, (13.04±2.41) mV, and (748.0±91.5) Ω at discharge, (0.40±0.06) V/0.24 ms, (14.26±4.11) mV, and (700.0±91.7) Ω at 1 month post-implant and (0.39±0.05) V/0.24 ms, 14.40±3.97 mV, and (682.0±96.0) Ω at 3 months post-implant, respectively. Threshold increase was ≤1.5 V compared to that during implantation, electrical parameters were acceptable and stable. There was no difference in LVEDD [(44.00±5.24) mm vs. (44.00±5.34) mm,P=1.000] and EF [(62.00±3.39)% vs. (62.20±3.56)%, P=0.861] before and 1 month post-implant. No incidence of access site complications, cardiac effusion/perforation, dislodgment or infections occurred during the 3 months. Conclusions: The leadless transcatheter pacemaker implantation performed in our study archived a high implant success rate and favorable safety profile as well as associated with low and stable pacing thresholds. The long-term safety and benefit of leadless pacemaker need to be evaluated in future clinical studies.

Harnessing sub-organelle metabolism for biosynthesis of isoprenoids in yeast

Current yeast metabolic engineering in isoprenoids production mainly focuses on rewiring of cytosolic metabolic pathway. However, the precursors, cofactors and the enzymes are distributed in various sub-cellular compartments, which may hamper isoprenoid biosynthesis. On the other side, pathway compartmentalization provides several advantages for improving metabolic flux toward target products. We here summarize the recent advances on harnessing sub-organelle for isoprenoids biosynthesis in yeast, and analyze the knowledge about the localization of enzymes, cofactors and metabolites for guiding the rewiring of the sub-organelle metabolism. This review may provide some insights for constructing efficient yeast cell factories for production of isoprenoids and even other natural products.

[Selection and effects of flap/myocutaneous flap repair methods for the defect after perineum tumor resection]

Objective: To explore the selection and effects of flap/myocutaneous flap repair methods for the defect after perineum tumor resection. Methods: From January 2011 to February 2017, 31 patients with vulvar tumor who were admitted to Hunan Cancer Hospital underwent repair of wound after tumor resection with various flaps/myocutaneous flaps. The patients were composed of 5 males and 26 females, aged 39-76 years, with 27 vulvar cancer and 4 Paget's disease in primary diseases. The size of defects after vulvar tumor radical resection ranged from 8.0 cm×4.5 cm to 27.5 cm×24.0 cm. According to the theory of perforasome, the defects were repaired by the external pudendal artery perforator flap, deep inferior epigastric artery perforator flap, rectus abdominis myocutaneous flap, anterolateral thigh flap, internal pudendal artery perforator flap, gracilis myocutaneous flap, and profunda artery perforator flap based on the specific size and location of perineum and groin where the defect was located. According to the blood supply zone of flap, totally 17 local translocation flaps, 18 axial flaps/myocutaneous flaps, and 7 V-Y advancement flaps were resected, with an area of 7.0 cm×4.0 cm to 21.0 cm×13.0 cm. All the flaps/myocutaneous flaps were transferred in pedicled fashion, and the donor sites were closed without tension. The number of flaps/myocutaneous flaps, wound closure, flaps/myocutaneous flaps survival, and follow-up were observed and recorded. Results: Altogether 42 flaps/myocutaneous flaps were harvested in 31 patients. Two flaps/myocutaneous flaps were used in 11 cases for large circular defect repair. All the defects achieved tension-free primary closure. The blood supply of 32 flaps/myocutaneous flaps was good, while insufficient blood supply was noted in the other 10 flaps/myocutaneous flaps. Seventeen flaps/myocutaneous flaps survived smoothly. Wound dehiscence occurred in 5 flaps/myocutaneous flaps 8 to 14 days postoperatively, which was healed with dressing change. Temporary congestion was noted in 7 flaps/myocutaneous flaps 2 to 5 days postoperatively, which recovered without special treatment. Three flaps/myocutaneous flaps had infection 7 to 15 days postoperatively, two of which recovered after dressing change, while the other one had partial necrosis and received debridement and direct closure. Two flaps/myocutaneous flaps were totally necrotic 8 to 15 days postoperatively, which were repaired with pedicled rectus abdominis myocutaneous flap after debridement. Seven flaps/myocutaneous flaps had partial necrosis 7 to 20 days postoperatively and were healed after dressing change. Twenty-four patients were followed up for 9-38 months. The color of flaps/myocutaneous flaps was similar to that of the surrounding skin, the shape of vulva was natural, the movement of hip joint was not limited, the function of micturition and defecation was not affected, and tumor recurrence was noted in 3 patients. Conclusions: For the complicated large defect after perineum tumor resection, the flexible application of different forms of flaps/myocutaneous flaps to repair according to different areas regains the appearance and function. However, there are many complications, so it is necessary to further strengthen the postoperative care.

[Diagnosis and therapeutic strategies for non-obese type of non-alcoholic fatty liver diseases]

Non-alcoholic fatty liver disease and obesity have interconnected genes, but it can also occur in non-obese population with body mass index < 25 kg/m(2). Non-obese type of non-alcoholic fatty liver disease mostly occurs in Asia. There is no significant difference between obese and non-obese type of non-alcoholic fatty liver in histological examination of liver biopsies. Visceral obesity, high fructose and cholesterol intake, and genetic factors such as APOC3 gene mutation are closely related to non-obese type of non-alcoholic fatty liver. Generally speaking, non-alcoholic steatohepatitis has an increased mortality rate, mainly due to cardiovascular causes, and has no link with other metabolic factors. Although data on the impact of mortality from non-obese type of non-alcoholic fatty liver disease are incomplete and limited, however diagnosis, management, and treatment may be important. Lifestyle changes to reduce visceral obesity, including dietary changes and physical activity, remain the main treatment options for patients with non-obese type of non-alcoholic fatty liver disease.