Pain control and neonatal outcomes in 211 women under epidural anesthesia during childbirth at high altitude in Qinghai, China.

Background: High altitudes are characterized by low-pressure oxygen deprivation. This is further exacerbated with increasing altitude. High altitudes can be associated with reduced oxygenation, which in turn, can affect labor, as well as maternal and fetal outcomes. Epidural anesthesia can significantly relieve labor pain. This study aimed to assess the effects of elevation gradient changes at high altitude on the analgesic effect of epidural anesthesia, labor duration, and neonatal outcomes. Methods: We divided 211 women who received epidural anesthesia into groups according to varying elevation of their residence (76 in Xining City, mean altitude 2,200 m; 63 in Haibei Prefecture, mean altitude 3,655 m; and 72 in Yushu Prefecture, mean altitude 4,493 m). The analgesic effect was assessed using a visual analog scale (VAS). Labor duration was objectively recorded. The neonatal outcome was assessed using Apgar scores and fetal umbilical artery blood pH. Results: VAS scores among the three groups did not differ significantly (p > 0.05). The neonatal Apgar scores in descending order were: Xining group > Haibei group > Yushu group (p < 0.05). The stage of labor was similar among the three groups (p > 0.05). Fetal umbilical artery blood pH in descending order were: Xining group > Haibei group > Yushu group (p < 0.05). Conclusion: Elevation gradient changes in highland areas did not affect the efficacy of epidural anesthesia or labor duration. However, neonatal outcomes were affected.

Flexible TAM requirement of TnpB enables efficient single-nucleotide editing with expanded targeting scope.

TnpBs encoded by the IS200/IS605 family transposon are among the most abundant prokaryotic proteins from which type V CRISPR-Cas nucleases may have evolved. Since bacterial TnpBs can be programmed for RNA-guided dsDNA cleavage in the presence of a transposon-adjacent motif (TAM), these nucleases hold immense promise for genome editing. However, the activity and targeting specificity of TnpB in homology-directed gene editing remain unknown. Here we report that a thermophilic archaeal TnpB enables efficient gene editing in the natural host. Interestingly, the TnpB has different TAM requirements for eliciting cell death and for facilitating gene editing. By systematically characterizing TAM variants, we reveal that the TnpB recognizes a broad range of TAM sequences for gene editing including those that do not elicit apparent cell death. Importantly, TnpB shows a very high targeting specificity on targets flanked by a weak TAM. Taking advantage of this feature, we successfully leverage TnpB for efficient single-nucleotide editing with templated repair. The use of different weak TAM sequences not only facilitates more flexible gene editing with increased cell survival, but also greatly expands targeting scopes, and this strategy is probably applicable to diverse CRISPR-Cas systems.

Combining CRISPR/Cas9 and natural excision for the precise and complete removal of mobile genetic elements in bacteria.

Horizontal gene transfer, facilitated by mobile genetic elements (MGEs), is an adaptive evolutionary process that contributes to the evolution of bacterial populations and infectious diseases. A variety of MGEs not only can integrate into the bacterial genome but also can survive or even replicate like plasmids in the cytoplasm, thus requiring precise and complete removal for studying their strategies in benefiting host cells. Existing methods for MGE removal, such as homologous recombination-based deletion and excisionase-based methods, have limitations in effectively eliminating certain MGEs. To overcome these limitations, we developed the Cas9-NE method, which combines the CRISPR/Cas9 system with the natural excision of MGEs. In this approach, a specialized single guide RNA (sgRNA) element is designed with a 20-nucleotide region that pairs with the MGE sequence. This sgRNA is expressed from a plasmid that also carries the Cas9 gene. By utilizing the Cas9-NE method, both the integrative and circular forms of MGEs can be precisely and completely eliminated through Cas9 cleavage, generating MGE-removed cells. We have successfully applied the Cas9-NE method to remove four representative MGEs, including plasmids, prophages, and genomic islands, from Vibrio strains. This new approach not only enables various investigations on MGEs but also has significant implications for the rapid generation of strains for commercial purposes.IMPORTANCEMobile genetic elements (MGEs) are of utmost importance for bacterial adaptation and pathogenicity, existing in various forms and multiple copies within bacterial cells. Integrated MGEs play dual roles in bacterial hosts, enhancing the fitness of the host by delivering cargo genes and potentially modifying the bacterial genome through the integration/excision process. This process can lead to alterations in promoters or coding sequences or even gene disruptions at integration sites, influencing the physiological functions of host bacteria. Here, we developed a new approach called Cas9-NE, allowing them to maintain the natural sequence changes associated with MGE excision. Cas9-NE allows the one-step removal of integrated and circular MGEs, addressing the challenge of eliminating various MGE forms efficiently. This approach simplifies MGE elimination in bacteria, expediting research on MGEs.

Efficacy and safety of nalbuphine for epidural labor analgesia at high altitude: An observational study.

Xining is located at the eastern edge of the Qinghai-Tibet Plateau, with an average altitude of >7000 feet (>2000 m). Nalbuphine is a kappa-opioid receptor agonist that can provide analgesia with fewer side effects than other opioid analgesics. This study aimed to evaluate pain control, side effects, and neonatal outcomes from combining nalbuphine with sufentanil and ropivacaine in 600 women during epidural anesthesia while giving birth at a high altitude in Xining, China. A total of 600 parturients receiving epidural labor analgesia were randomly divided into 2 groups, each group 300 parturients. The nalbuphine group received nalbuphine, sufentanil, and ropivacain, the control group only received sufentanil and ropivacain. The analgesic effect was evaluated through the Visual Analogue Scale scores. Neonatal outcomes were mainly evaluated through the Apgar Scores. Compared to the control group, the nalbuphine group showed lower Visual Analogue Scale scores at all time points after analgesia (P < .05). In comparison with the control group, parturients in the nalbuphine group showed lower incidence rates of fever at delivery, 24-hour postpartum bleeding, and pruritus (P < .05). However, between the 2 groups, there were no statistically significant differences in the remaining maternal and infant outcomes and neonatal outcomes (P > .05). Moreover, no adverse effects on neonatal outcomes were observed. The findings from this study support findings from previous studies that nalbuphine provided safe epidural analgesia without significant side effects for the mother and infant, and showed both safety and efficacy when used during labor at high altitude.

Genomic Island-Encoded Diguanylate Cyclase from Vibrio alginolyticus Regulates Biofilm Formation and Motility in Pseudoalteromonas.

Many bacteria use the second messenger c-di-GMP to regulate exopolysaccharide production, biofilm formation, motility, virulence, and other phenotypes. The c-di-GMP level is controlled by the complex network of diguanylate cyclases (DGCs) and phosphodiesterases (PDEs) that synthesize and degrade c-di-GMP. In addition to chromosomally encoded DGCs, increasing numbers of DGCs were found to be located on mobile genetic elements. Whether these mobile genetic element-encoded DGCs can modulate the physiological phenotypes in recipient bacteria after horizontal gene transfer should be investigated. In our previous study, a genomic island encoding three DGC proteins (Dgc137, Dgc139, and Dgc140) was characterized in Vibrio alginolyticus isolated from the gastric cavity of the coral Galaxea fascicularis. Here, the effect of the three DGCs in four Pseudoalteromonas strains isolated from coral Galaxea fascicularis and other marine environments was explored. The results showed that when dgc137 is present rather than the three DGC genes, it obviously modulates biofilm formation and bacterial motility in these Pseudoalteromonas strains. Our findings implied that mobile genetic element-encoded DGC could regulate the physiological status of neighboring bacteria in a microbial community by modulating the c-di-GMP level after horizontal gene transfer.

Minimized antibiotic-free plasmid vector for gene therapy utilizing a new toxin-antitoxin system.

Approaches to improve plasmid-mediated transgene expression are needed for gene therapy and genetic immunization applications. The backbone sequences needed for the production of plasmids in bacterial hosts and the use of antibiotic resistance genes as selection markers represent biological safety risks. Here, we report the development of an antibiotic-free expression plasmid vector with a minimized backbone utilizing a new toxin-antitoxin (TA) system. The Rs_0636/Rs_0637 TA pair was derived from the coral-associated bacterium Roseivirga sp. The toxin gene is integrated into the chromosome of Escherichia coli host cells, and a recombinant mammalian expression plasmid is constructed by replacing the antibiotic resistance gene with the antitoxin gene Rs_0637 (here named Tiniplasmid). The Tiniplasmid system affords high selection efficiency (∼80%) for target gene insertion into the plasmid and has high plasmid stability in E. coli (at least 9 days) in antibiotic-free conditions. Furthermore, with the aim of reducing the size of the backbone sequence, we found that the antitoxin gene can be reduced to 153 bp without a significant reduction in selection efficiency. To develop its applications in gene therapy and DNA vaccines, the biosafety and efficiency of the Tiniplasmid-based eukaryotic gene delivery and expression were further evaluated in CHO-K1 cells. The results showed that Rs_0636/Rs_0637 has no cell toxicity and that the Tiniplasmid vector has a higher gene expression efficiency than the commercial vectors pCpGfree and pSTD in the eukaryotic cells. Altogether, the results demonstrate the potential of the Rs_0636/Rs_0637-based antibiotic-free plasmid vector for the development and production of safe and efficacious DNA vaccines.

Comparative genomic insights into habitat adaptation of coral-associated Prosthecochloris.

Green sulfur bacteria (GSB) are a distinct group of anoxygenic phototrophic bacteria that are found in many ecological niches. Prosthecochloris, a marine representative genus of GSB, was found to be dominant in some coral skeletons. However, how coral-associated Prosthecochloris (CAP) adapts to diurnal changing microenvironments in coral skeletons is still poorly understood. In this study, three Prosthecochloris genomes were obtained through enrichment culture from the skeleton of the stony coral Galaxea fascicularis. These divergent three genomes belonged to Prosthecochloris marina and two genomes were circular. Comparative genomic analysis showed that between the CAP and non-CAP clades, CAP genomes possess specialized metabolic capacities (CO oxidation, CO2 hydration and sulfur oxidation), gas vesicles (vertical migration in coral skeletons), and cbb 3-type cytochrome c oxidases (oxygen tolerance and gene regulation) to adapt to the microenvironments of coral skeletons. Within the CAP clade, variable polysaccharide synthesis gene clusters and phage defense systems may endow bacteria with differential cell surface structures and phage susceptibility, driving strain-level evolution. Furthermore, mobile genetic elements (MGEs) or evidence of horizontal gene transfer (HGT) were found in most of the genomic loci containing the above genes, suggesting that MGEs play an important role in the evolutionary diversification between CAP and non-CAP strains and within CAP clade strains. Our results provide insight into the adaptive strategy and population evolution of endolithic Prosthecochloris strains in coral skeletons.

Genome-Wide Association Study for Idiopathic Ventricular Tachyarrhythmias Identifies Key Role of CCR7 and PKN2 in Calcium Homeostasis and Cardiac Rhythm Maintenance.

BACKGROUND: Idiopathic ventricular tachycardia (VT) occurs in structurally normal hearts and accounts for a significant number of all types of VT. The genome-wide association study is the most effective strategy for identifying novel genetic variants for common diseases. However, no genome-wide association study has been reported for idiopathic VT. METHODS: We conducted the first genome-wide association study for idiopathic VT in the Chinese Han population using a discovery population with 246 cases and 648 controls and a replication population with 222 cases and >4072 controls. Candidate VT genes were functionally characterized in zebrafish. Real-time RT-PCR analysis was used to determine the effects of candidate genes on expression of ion channels and regulators. Patch-clamping was used to record L-type calcium current from neonatal rat cardiomyocytes with overexpression of candidate genes. RESULTS: We identified 4 significant loci represented by rs78960694 (minor allele frequency [MAF]=5.02% in cases and 1.84% in controls; P=4.30×10-12, odds ratio [OR]=3.91) and rs2229095 (MAF=3.25% in cases and 1.63% in controls; P=1.02×10-7, OR=3.44) near and in CCR7, respectively, rs68126098 in NELL1 (MAF=40.98% in cases and 32.07% in controls; P=2.40×10-8, OR=1.53), rs2390325 between PKN2 and LMO4 (MAF=21.19% in cases and 15.12% in controls; P=1.92×10-7, OR=1.62), and rs270065 in CSMD1 (MAF=33.63% in cases and 40.25% in controls; P=9.51×10-7, OR=0.69). Note that the associations of idiopathic VT for CCR7 variant rs78960694 and NELL1 variant rs68126098 reach genome-wide significance (P<5.00×10-8). Overexpression of either PKN2 or CCR7 increased the heart rate in zebrafish, and enhanced expression of CACNA1C, RYR2, or NOS1AP in zebrafish embryos, HEK293, and AC16 cardiomyocytes. Overexpression of either PKN2 or CCR7 significantly increased L-type Ca2+ current density. CONCLUSIONS: The first genome-wide association study identifies 4 novel loci and 2 risk genes (PKN2 and CCR7) for idiopathic VT. These findings identify new molecular determinants for cardiac calcium homeostasis and rhythm maintenance and provide novel targets for diagnosis and treatment for idiopathic VT.

The coral pathogen Vibrio coralliilyticus kills non-pathogenic holobiont competitors by triggering prophage induction.

The coral reef microbiome is central to reef health and resilience. Competitive interactions between opportunistic coral pathogens and other commensal microbes affect the health of coral. Despite great advances over the years in sequencing-based microbial profiling of healthy and diseased coral, the molecular mechanism underlying colonization competition has been much less explored. In this study, by examining the culturable bacteria inhabiting the gastric cavity of healthy Galaxea fascicularis, a scleractinian coral, we found that temperate phages played a major role in mediating colonization competition in the coral microbiota. Specifically, the non-toxigenic Vibrio sp. inhabiting the healthy coral had a much higher colonization capacity than the coral pathogen Vibrio coralliilyticus, yet this advantage was diminished by the latter killing the former. Pathogen-encoded LodAB, which produces hydrogen peroxide, triggers the lytic cycle of prophage in the non-toxicogenic Vibrio sp. Importantly, V. coralliilyticus could outcompete other coral symbiotic bacteria (for example, Endozoicomonas sp.) through LodAB-dependent prophage induction. Overall, we reveal that LodAB can be used by pathogens as an important weapon to gain a competitive advantage over lysogenic competitors when colonizing corals.

Mobile genetic elements used by competing coral microbial populations increase genomic plasticity.

Intraspecies diversification and niche adaptation by members of the Vibrio genus, one of the most diverse bacterial genera, is thought to be driven by horizontal gene transfer. However, the intrinsic driving force of Vibrio species diversification is much less explored. Here, by studying two dominant and competing cohabitants of the gastric cavity of corals, we found that a phenotype influencing island (named VPII) in Vibrio alginolyticus was eliminated upon coculturing with Pseudoalteromonas. The loss of VPII reduced the biofilm formation and phage resistance, but activated motility, which may allow V. alginolyticus to expand to other niches. Mechanistically, we discovered that the excision of this island is mediated by the cooperation of two unrelated mobile genetic elements harbored in Pseudoalteromonas spp., an integrative and conjugative element (ICE) and a mobilizable genomic island (MGI). More importantly, these mobile genetic elements are widespread in cohabitating Gram-negative bacteria. Altogether, we discovered a new strategy by which the mobilome is employed by competitors to increase the genomic plasticity of rivals.

The HipAB Toxin-Antitoxin System Stabilizes a Composite Genomic Island in Shewanella putrefaciens CN-32.

Composite genomic islands (GIs) are useful models for studying GI evolution if they can revert into the previous components. In this study, CGI48-a 48,135-bp native composite GI that carries GI21, whose homologies specifically integrated in the conserved yicC gene-were identified in Shewanella putrefaciens CN-32. CGI48 was integrated into the tRNATrp gene, which is a conserved gene locus for the integration of genomic islands in Shewanella. Upon expressing integrase and excisionase, CGI48 and GI21 are excised from chromosomes via site-specific recombination. The shorter attachment sites of GI21 facilitated the capture of GI21 into CGI48. Moreover, GI21 encodes a functional HipAB toxin-antitoxin system, thus contributing to the maintenance of CGI48 in the host bacteria. This study provides new insights into GI evolution by performing the excision process of the inserting GI and improves our understanding of the maintenance mechanisms of composite GI.

Functional rare variant in a C/EBPbeta binding site in NINJ2 gene increases the risk of coronary artery disease.

OBJECTIVE: NINJ2 regulates activation of vascular endothelial cells, and genome-wide association studies showed that variants in NINJ2 confer risk to stroke. However, whether variants in NINJ2 are associated with coronary artery disease (CAD) is unknown. METHODS: We genotyped rs34166160 in NINJ2 in two independent Chinese GeneID populations which included 2,794 CAD cases and 4,131 controls, and performed genetics association studies. Functional studies were also performed to reveal the mechanisms. RESULTS: Allele rs34166160 significantly confers risk to CAD in the GeneID Hubei population which contained 1,440 CAD cases and 2,660 CAD-free controls (observed P-obs = 6.39 × 10-3 with an odds ratio (OR) was 3.39, adjusted P-adj = 8.12 × 10-3 with an OR of 3.10). The association was replicated in another population, GeneID Shandong population contained 1,354 CAD cases and 1,471 controls (P-obs = 3.33 × 10-3 with an OR of 3.14, P-adj = 0.01 with an OR of 2.74). After combining the two populations, the association was more significant (P-obs = 1.57 × 10-5 with an OR of 3.58, P-adj = 3.41 × 10-4 with an OR of 2.80). In addition, we found that rs34166160 was associated with the mRNA expression level of NINJ2 and the flanking region of rs34166160 can directly bind with transcriptional factor CCAAT-box/enhancer-binding protein beta, and the risk A allele has more transcription activity than non-risk C allele with or without LPS in HUVEC cells. CONCLUSIONS: Our study demonstrates that the functional rare variant rs34166160 in NINJ2 confers risk to CAD for the first time, and these findings further expand the range of the pathology of CAD and atherosclerosis.

Prophage Tracer: precisely tracing prophages in prokaryotic genomes using overlapping split-read alignment.

The life cycle of temperate phages includes a lysogenic cycle stage when the phage integrates into the host genome and becomes a prophage. However, the identification of prophages that are highly divergent from known phages remains challenging. In this study, by taking advantage of the lysis-lysogeny switch of temperate phages, we designed Prophage Tracer, a tool for recognizing active prophages in prokaryotic genomes using short-read sequencing data, independent of phage gene similarity searching. Prophage Tracer uses the criterion of overlapping split-read alignment to recognize discriminative reads that contain bacterial (attB) and phage (attP) att sites representing prophage excision signals. Performance testing showed that Prophage Tracer could predict known prophages with precise boundaries, as well as novel prophages. Two novel prophages, dsDNA and ssDNA, encoding highly divergent major capsid proteins, were identified in coral-associated bacteria. Prophage Tracer is a reliable data mining tool for the identification of novel temperate phages and mobile genetic elements. The code for the Prophage Tracer is publicly available at https://github.com/WangLab-SCSIO/Prophage_Tracer.

Conjugative plasmid-encoded toxin-antitoxin system PrpT/PrpA directly controls plasmid copy number.

Toxin-antitoxin (TA) loci were initially identified on conjugative plasmids, and one function of plasmid-encoded TA systems is to stabilize plasmids or increase plasmid competition via postsegregational killing. Here, we discovered that the type II TA system, Pseudoalteromonas rubra plasmid toxin-antitoxin PrpT/PrpA, on a low-copy-number conjugative plasmid, directly controls plasmid replication. Toxin PrpT resembles ParE of plasmid RK2 while antitoxin PrpA (PF03693) shares no similarity with previously characterized antitoxins. Surprisingly, deleting this prpA-prpT operon from the plasmid does not result in plasmid segregational loss, but greatly increases plasmid copy number. Mechanistically, the antitoxin PrpA functions as a negative regulator of plasmid replication, by binding to the iterons in the plasmid origin that inhibits the binding of the replication initiator to the iterons. We also demonstrated that PrpA is produced at a higher level than PrpT to prevent the plasmid from overreplicating, while partial or complete degradation of labile PrpA derepresses plasmid replication. Importantly, the PrpT/PrpA TA system is conserved and is widespread on many conjugative plasmids. Altogether, we discovered a function of a plasmid-encoded TA system that provides new insights into the physiological significance of TA systems.

Specificity and application of SOX2 antibody.

Sox2 is known to play an important role in maintaining the totipotency and self-renewal of embryonic stem cells. The purpose of this study was to prepare an anti-chicken Sox2 polyclonal antibody using prokaryotic expression techniques, to evaluate its specificity and to use it to investigate the expression and distribution of Sox2 in the chicken brain and lungs. The chicken Sox2 gene was amplified and subcloned to a pET-30a vector to construct a prokaryotic expression vector, pET-Sox2. A His-Sox2 fusion protein was expressed, purified, and used to prepare an antichicken Sox2 polyclonal antibody. Western blotting revealed that the antichicken Sox2 antibody could specifically bind not only to the purified His-Sox2 fusion protein but also to the endogenous Sox2 protein in the testes of chicken, showing a distinct dose-dependent relationship between antigen and Sox2 antibody. Indirect immunofluorescent staining of Sox2-overexpressing cells showed strong nuclear and diffuse cytoplasmic immunoreactivity for Sox2 in the antichicken Sox2 antibody-staining cells. A CRISPR/Cas9 effector system-mediated Sox2 knockdown assay indicated that Sox2 expression in HEK 293T cells was downregulated in the presence of doxycycline but upregulated in the absence of doxycycline. In addition, cryosectioning and immunohistochemical staining illustrated that most spermatogonia in the seminiferous tubules, and a small number of Sertoli and Leydig cells, were positive for Sox2. The antichicken Sox2 antibody was also successfully used to investigate the expression and distribution of Sox2 in the chicken cerebellar cortex, optic tectum, cerebral cortex, and lungs. The results of this study confirmed the specificity of the antichicken Sox2 polyclonal antibody, which will be available for the study of biological functions of the chicken Sox2 gene and the self-renewal mechanisms of chicken pluripotent stem cells.

SNP rs2243828 in MPO associated with myeloperoxidase level and atrial fibrillation risk in Chinese Han population.

Previous studies shown that myeloperoxidase (MPO) level is higher in patients with atrial fibrillation (AF); however, no genetic evidence between MPO and AF risk in human population was observed. Therefore, the present study was aimed to investigate the association between rs2243828, a variant in promoter region of MPO and the risk of AF in Chinese GeneID population. The results demonstrated that the minor G allele of rs2243828 showed a significant association with AF in two independent population (GeneID-north population with 694 AF cases and 710 controls, adjusted P-adj = 6.25 × 10-3 with an odds ratio was 0.77, GeneID-central population with 1106 cases and 1501 controls, P-adj = 9.88 × 10-5 with an odds ratio was 0.75). The results also showed G allele was significantly associated with lower plasma concentration of myeloperoxidase in general population. We also observed a significant difference of odds ratio between subgroups of hypertension and non-hypertension. Therefore, our findings identified variant in MPO associated with risk of AF and it may give strong evidence to link the inflammation with the incidence of AF.

Eliminating mcr-1-harbouring plasmids in clinical isolates using the CRISPR/Cas9 system.

OBJECTIVES: To eliminate mcr-1-harbouring plasmids and MDR plasmids in clinical Escherichia coli isolates. METHODS: Plasmid pMBLcas9 expressing Cas9 was constructed and used to clone target single-guide RNAs (sgRNAs) for plasmid curing. The recombinant plasmid pMBLcas9-sgRNA was transferred by conjugation into two clinical E. coli isolates. The curing efficiency of different sgRNAs targeting conserved genes was tested. The elimination of targeted plasmids and the generation of transposase-mediated recombination of p14EC033a variants were characterized by PCR and DNA sequencing. RESULTS: In this study, four native plasmids in isolate 14EC033 and two native plasmids in isolate 14EC007 were successfully eliminated in a step-by-step manner using pMBLcas9. Moreover, two native plasmids in 14EC007 were simultaneously eliminated by tandemly cloning multiple sgRNAs in pMBLcas9, sensitizing 14EC007 to polymyxin and carbenicillin. In 14EC033 with two mcr-1-harbouring plasmids, IncI2 plasmid p14EC033a and IncX4 plasmid p14EC033b, a single mcr-1 sgRNA mediated the loss of p14EC033b and generated a mutant p14EC033a in which the mcr-1 gene was deleted. An insertion element, IS5, located upstream of mcr-1 in p14EC033a was responsible for transposase-mediated recombination, resulting in mcr-1 gene deletion instead of plasmid curing. CONCLUSIONS: CRISPR/Cas9 can be used to efficiently sensitize clinical isolates to antibiotics in vitro. For isolates with multiple plasmids, the CRISPR/Cas9 approach can either remove each plasmid in a stepwise manner or simultaneously remove multiple plasmids in one step. Moreover, this approach can be used to delete multiple gene copies by using only one sgRNA. However, caution must be exercised to avoid unwanted recombination events during genetic manipulation.

Biofilm formation in Pseudoalteromonas lipolytica is related to IS5-like insertions in the capsular polysaccharide operon.

Bacterial capsular polysaccharides (CPSs) participate in environmental adaptation in diverse bacteria species. However, the role and regulation of CPS production in marine bacteria have remained largely unexplored. We previously reported that both wrinkled and translucent Pseudoalteromonas lipolytica variants with altered polysaccharide production were generated in pellicle biofilm-associated cells. In this study, we observed that translucent variants were generated at a rate of ∼20% in colony biofilms of P. lipolytica cultured on HSLB agar plates for 12 days. The DNA sequencing results revealed that nearly 90% of these variants had an IS5-like element inserted within the coding or promoter regions of nine genes in the cps operon. In contrast, IS5 insertion into the cps operon was not detected in planktonic cells. Furthermore, we demonstrated that the IS5 insertion event inactivated CPS production, which leads to a translucent colony morphology. The CPS-deficient variants showed an increased ability to form attached biofilms but exhibited reduced resistance to sublethal concentrations of antibiotics. Moreover, deleting the DNA repair gene recA significantly decreased the frequency of occurrence of CPS-deficient variants during biofilm formation. Thus, IS insertion into the cps operon is an important mechanism for the production of genetic variants during biofilm formation of marine bacteria.

Significant association of rare variant p.Gly8Ser in cardiac sodium channel ß4-subunit SCN4B with atrial fibrillation.

Atrial fibrillation (AF) affects 33.5 million individuals worldwide. It accounts for 15% of strokes and increases risk of heart failure and sudden death. The voltage-gated cardiac sodium channel complex is responsible for the generation and conduction of the cardiac action potential, and composed of the main pore-forming α-subunit Nav 1.5 (encoded by the SCN5A gene) and one or more auxiliary ß-subunits, including Nav ß1 to Nav ß4 encoded by SCN1B to SCN4B, respectively. We and others identified loss-of-function mutations in SCN1B and SCN2B and dominant-negative mutations in SCN3B in patients with AF. Three missense variants in SCN4B were identified in sporadic AF patients and small nuclear families; however, the association between SCN4B variants and AF remains to be further defined. In this study, we performed mutational analysis in SCN4B using a panel of 477 AF patients, and identified one nonsynonymous genomic variant p.Gly8Ser in four patients. To assess the association between the p.Gly8Ser variant and AF, we carried out case-control association studies with two independent populations (944 AF patients vs. 9,81 non-AF controls in the first discovery population and 732 cases and 1,291 controls in the second replication population). Significant association was identified in the two independent populations and in the combined population (p = 4.16 × 10-4 , odds ratio [OR] = 3.14) between p.Gly8Ser and common AF as well as lone AF (p = 0.018, OR = 2.85). These data suggest that rare variant p.Gly8Ser of SCN4B confers a significant risk of AF, and SCN4B is a candidate susceptibility gene for AF.