Fused in sarcoma regulates glutamate signaling and oxidative stress response.

Mutations in fused in sarcoma (fust-1) are linked to ALS. However, how these ALS causative mutations alter physiological processes and lead to the onset of ALS remains largely unknown. By obtaining humanized fust-1 ALS mutations via CRISPR-CAS9, we generated a C. elegans ALS model. Homozygous fust-1 ALS mutant and fust-1 deletion animals are viable in C. elegans. This allows us to better characterize the molecular mechanisms of fust-1-dependent responses. We found FUST-1 plays a role in regulating superoxide dismutase, glutamate signaling, and oxidative stress. FUST-1 suppresses SOD-1 and VGLUT/EAT-4 in the nervous system. FUST-1 also regulates synaptic AMPA-type glutamate receptor GLR-1. We found that fust-1 ALS mutations act as loss-of-function in SOD-1 and VGLUT/EAT-4 phenotypes, whereas the fust-1 ALS mutations act as gain-of-function in redox homeostasis and the microbe-induced oxidative stress response. We hypothesized that FUST-1 is a link between glutamate signaling and SOD-1. Our results may provide new insights into the human ALS alleles and their roles in pathological mechanisms that lead to ALS.

First Tarsometatarsal Joint Fusion for Hallux Valgus Deformity: A Retrospective Comparison of Two Fixation Constructs Regarding Initial Maintenance of Correction and Complications: Traditional Crossing Screw Fixation Versus Dorsomedial Locking Plate and Intercuneiform Compression Screw.

Various fixation constructs exist to address hallux valgus when performing a first tarsometatarsal joint arthrodesis. The goal of this present study is to compare complication rates, and degree and maintenance of angular correction between a dorsomedial locking plate with intercuneiform compression screw construct versus traditional crossing solid screw fixation construct. The plate plus intercuneiform compression screw construct fixation utilized a combined sagittal saw and curette method of joint preparation while the crossed screw fixation group utilized a curette and bur technique. A retrospective review was conducted of consecutive patients who underwent a midfoot fusion using either constructs. Sixty four total feet in 56 patients were enrolled in the study. Twenty four consecutive patients (32 feet) who underwent a midfoot arthrodesis using the locking plate and intercuneiform fixation were fully fused (100%) by 10 weeks postoperatively, with no incidents of nonunion and one deep vein thrombosis event. Thirty two consecutive patients (32 feet) who underwent midfoot arthrodesis with crossing screw fixation had 2 nonunion events, one that was asymptomatic and the other that required a revision midfoot fusion. There was a statistically significant improvement from the pre-operative intermetatarsal angle, hallux abductus angle compared to the 10 week and 1 year radiographs (p < .05) for the entire cohort for both fixation constructs. There was a statistically significant increase in American College of Foot and Ankle Surgery first ray scores from pre-op to 1 year follow-up for both fixation constructs. Overall, the dorsomedial locking plate plus intercuneiform compression screw fixation construct better maintains Intermetatarsal angle (IMA) correction at midterm follow-up compared to the traditional crossing screw construct. Both cohorts overall demonstrate similar fusion rates at 10 weeks, nonunion events, incidences of broken hardware, hardware removal, deep vein thrombosis, neuritis at 1 year postoperatively, and hallux varus.

Superoxide dismutase SOD-3 regulates redox homeostasis in the intestine.

There are four cellular superoxide dismutase paralogs in C. elegans . The role of these superoxide dismutases in redox homeostasis remains largely unknown. Here, we generated the integrated redox reporter rxRFP to detect changes in redox homeostasis using live fluorescence imaging. We found that sod-3 deletion contributes to oxidative stress elevation. Deletions in additional paralogs ameliorate the oxidative stress of sod-3 . Complete elimination of all four paralogs elicits the same increase in rxRFP fluorescence as in the sod-3 single mutation, suggesting a compensatory role of other sod s. Our results suggest that SOD-3 plays a key role in regulating gut redox homeostasis.

Glutamate signaling mediates C. elegans behavioral plasticity to pathogens.

In Caenorhabditis elegans, sensory neurons mediate behavioral response to pathogens. However, how C. elegans intergrades these sensory signals via downstream neuronal and molecular networks remains largely unknown. Here, we report that glutamate transmission mediates behavioral plasticity to Pseudomonas aeruginosa. Deletion in VGLUT/eat-4 renders the mutant animals unable to elicit either an attractive or an aversive preference to a lawn of P. aeruginosa. AMPA-type glutamate receptor GLR-1 promotes the avoidance response to P. aeruginosa. SOD-1 acts downstream of GLR-1 in the cholinergic motor neurons. SOD-1 forms a punctate structure and is localized next to GLR-1 at the ventral nerve cord. Finally, single-copy ALS-causative sod-1 point mutation acts as a loss-of-function allele in both pathogen avoidance and glr-1 dependent phenotypes. Our data showed a link between glutamate signaling and redox homeostasis in C. elegans pathogen response and may provide potential insights into the pathology triggered by oxidative stress in the nervous system.

A Novel Manipulation Technique for Lapidus Fusion in Correction of Hallux Valgus Deformity With Underlying Metatarsus Adductus: A Case Series.

Underlying metatarsus adductus (MA) is commonly seen in patients with hallux valgus (HV) deformity, with implications regarding procedure selection and hallux valgus recurrence. Lapidus, or first tarsometatarsal fusion, is commonly performed allowing reduction in intermetatarsal angle (IMA) but this procedure has not been established as an approach to provide partial correction of MA deformity. Retrospective assessment of preoperative and postoperative metatarsus adductus angle (MAA), IMA and hallux abductus angle (HAA) in patients treated with Lapidus fusion for HV. Significance was determined via paired t test with a p value of <.05. All cases involved manual transverse plane manipulation to reduce both IMA and MAA during screw insertion. Intermetatarsal angle and Engel's angle were measured on preoperative AP radiographs to determine the presence of underlying MA in patients undergoing Lapidus fusion for HV. Ten weeks and 1 year postoperative radiographs were measured to determine degree of correction of IMA, HAA, and MAA. Thirty-four patients met inclusion criteria, which is approximately 46% of our sample population. The average preoperative IMA was 19.4˚ (range 12-32) and the average postoperative IMA was 9.7˚ (range 6-14). The average preoperative Engel's angle was 27.4˚ (range 24-34) and the average postoperative Engel's angle was 22.6˚ (range 15-28) with mean improvement in MA of 6.6˚. Of the 34, 27 (79.4%) patients had a normal Engel's angle at 10 weeks postoperatively. All measures of change met level of significance (p < .05). Of the 34 patients, 21 had radiographs taken beyond the 1 year mark (average 53 weeks). These patients were found to have an average Engel's angle of 23.0˚, which is not statistically significantly different from their 10 week measurements. Of the 21 patients, 17 (81%) maintained normal Engel's angle past 1 year. Metatarsus adductus varies regarding degree of reducibility and complicates preoperative angular measurement and correction of HV. Based on these findings, we recommend Lapidus fusion using this specified manipulation technique to obtain comprehensive transverse plane correction.

A Review of Consecutive Cases to Identify the Rate of Underlying Osteomyelitis in Patients Undergoing Surgical Treatment of Gangrene of the Forefoot and Impact of Acute Infection on Outcome Following Amputation.

Medical literature offers no clear treatment guidelines when performing amputations for gangrene of the forefoot despite a high percentage that suffer poor outcome due to infection. Gas gangrene and wet gangrene are often preceded by dry stable gangrene. This is a retrospective review of consecutive patients who underwent forefoot amputation and bone biopsy as treatment of forefoot gangrene by a single surgeon. Procedures performed included digital, ray, or transmetatarsal amputation with bone biopsy sent for both culture and histopathologic evaluation. One hundred patients (35 females, 65 males) met inclusion criteria. Mean follow-up was 9.6 months. Mean age was 63.5 years old. Forty-six out of 100 (46%) had elective amputation while 54/100 (54%) were emergent for acute infection. Vascular intervention was performed in 52/100 (52%). Seventy-eight out of 100 (78%) had histopathologic diagnosis of acute osteomyelitis while 82/100 (82%) had positive bone culture. Patients with acute infection had worse outcomes, with higher rates of more proximal amputation and delayed wound healing. We found that 79.7% of patients who underwent forefoot amputation due to gangrene had underlying osteomyelitis. We also found that those with acute infection during the time of amputation had poorer postamputation outcomes such as delayed wound healing, revision surgery, and high rates of more proximal amputation. Therefore, it may imply that earlier amputation of stable gangrene prior to becoming acutely infected may decrease the occurrence of osteomyelitis and avoid some of the preventable postamputation complications. Further studies are warranted.

Neuron-specific regulation of superoxide dismutase amid pathogen-induced gut dysbiosis.

Superoxide dismutase, an enzyme that converts superoxide into less-toxic hydrogen peroxide and oxygen, has been shown to mediate behavioral response to pathogens. However, it remains largely unknown how superoxide dismutase is regulated in the nervous system amid pathogen-induced gut dysbiosis. Although there are five superoxide dismutases in C. elegans, our genetic analyses suggest that SOD-1 is the primary superoxide dismutase to mediate the pathogen avoidance response. When C. elegans are fed a P. aeruginosa diet, the lack of SOD-1 contributes to enhanced lethality. We found that guanylyl cyclases GCY-5 and GCY-22 and neuropeptide receptor NPR-1 act antagonistically to regulate SOD-1 expression in the gustatory neuron ASER. After C. elegans ingests a diet that contributes to high levels of oxidative stress, the temporal regulation of SOD-1 and the SOD-1-dependent response in the gustatory system demonstrates a sophisticated mechanism to fine-tune behavioral plasticity. Our results may provide the initial glimpse of a strategy by which a multicellular organism copes with oxidative stress amid gut dysbiosis.

Superoxide dismutase SOD-1 modulates C. elegans pathogen avoidance behavior.

The C. elegans nervous system mediates protective physiological and behavioral responses amid infection. However, it remains largely unknown how the nervous system responds to reactive oxygen species (ROS) activated by pathogenic microbes during infection. Here, we show superoxide dismutase-1 (SOD-1), an enzyme that converts superoxide into less toxic hydrogen peroxide and oxygen, functions in the gustatory neuron ASER to mediate C. elegans pathogen avoidance response. When C. elegans first encounters pathogenic bacteria P. aeruginosa, SOD-1 is induced in the ASER neuron. After prolonged P. aeruginosa exposure, ASER-specific SOD-1 expression is diminished. In turn, C. elegans starts to vacate the pathogenic bacteria lawn. Genetic knockdown experiments reveal that pathogen-induced ROS activate sod-1 dependent behavioral response non cell-autonomously. We postulate that the delayed aversive response to detrimental microbes may provide survival benefits by allowing C. elegans to temporarily utilize food that is tainted with pathogens as an additional energy source. Our data offer a mechanistic insight into how the nervous system mediates food-seeking behavior amid oxidative stress and suggest that the internal state of redox homeostasis could underlie the behavioral response to harmful microbial species.

Natural polymorphisms in C. elegans HECW-1 E3 ligase affect pathogen avoidance behaviour.

Heritable variation in behavioural traits generally has a complex genetic basis, and thus naturally occurring polymorphisms that influence behaviour have been defined only in rare instances. The isolation of wild strains of Caenorhabditis elegans has facilitated the study of natural genetic variation in this species and provided insights into its diverse microbial ecology. C. elegans responds to bacterial infection with conserved innate immune responses and, although lacking the immunological memory of vertebrate adaptive immunity, shows an aversive learning response to pathogenic bacteria. Here, we report the molecular characterization of naturally occurring coding polymorphisms in a C. elegans gene encoding a conserved HECT domain-containing E3 ubiquitin ligase, HECW-1. We show that two distinct polymorphisms in neighbouring residues of HECW-1 each affect C. elegans behavioural avoidance of a lawn of Pseudomonas aeruginosa. Neuron-specific rescue and ablation experiments and genetic interaction analysis indicate that HECW-1 functions in a pair of sensory neurons to inhibit P. aeruginosa lawn avoidance behaviour through inhibition of the neuropeptide receptor NPR-1 (ref. 10), which we have previously shown promotes P. aeruginosa lawn avoidance behaviour. Our data establish a molecular basis for natural variation in a C. elegans behaviour that may undergo adaptive changes in response to microbial pathogens.

Conserved genes act as modifiers of invertebrate SMN loss of function defects.

Spinal Muscular Atrophy (SMA) is caused by diminished function of the Survival of Motor Neuron (SMN) protein, but the molecular pathways critical for SMA pathology remain elusive. We have used genetic approaches in invertebrate models to identify conserved SMN loss of function modifier genes. Drosophila melanogaster and Caenorhabditis elegans each have a single gene encoding a protein orthologous to human SMN; diminished function of these invertebrate genes causes lethality and neuromuscular defects. To find genes that modulate SMN function defects across species, two approaches were used. First, a genome-wide RNAi screen for C. elegans SMN modifier genes was undertaken, yielding four genes. Second, we tested the conservation of modifier gene function across species; genes identified in one invertebrate model were tested for function in the other invertebrate model. Drosophila orthologs of two genes, which were identified originally in C. elegans, modified Drosophila SMN loss of function defects. C. elegans orthologs of twelve genes, which were originally identified in a previous Drosophila screen, modified C. elegans SMN loss of function defects. Bioinformatic analysis of the conserved, cross-species, modifier genes suggests that conserved cellular pathways, specifically endocytosis and mRNA regulation, act as critical genetic modifiers of SMN loss of function defects across species.