Mutations to the BTN2A1 Linker Region Impact Its Homodimerization and Its Cytoplasmic Interaction with Phospho-Antigen-Bound BTN3A1.

Intracellular binding of small-molecule phospho-Ags to the HMBPP receptor complex in infected cells leads to extracellular detection by T cells expressing the Vγ9Vδ2 TCR, a noncanonical method of Ag detection. The butyrophilin proteins BTN2A1 and BTN3A1 are part of the complex; however, their precise roles are unclear. We suspected that BTN2A1 and BTN3A1 form a tetrameric (dimer of dimers) structure, and we wanted to probe the importance of the BTN2A1 homodimer. We analyzed mutations to human BTN2A1, using internal domain or full-length BTN2A1 constructs, expressed in Escherichia coli or human K562 cells, that might disrupt its structure and/or function. Although BTN2A1 is a disulfide-linked homodimer, mutation of cysteine residues C247 and C265 did not affect the ability to stimulate T cell IFN-γ production by ELISA. Two mutations of the juxtamembrane region (at EKE282) failed to impact BTN2A1 function. In contrast, single point mutations (L318G and L325G) near the BTN2A1 B30.2 domain blocked phospho-Ag response. Size exclusion chromatography and nuclear magnetic resonance (NMR) experiments showed that the isolated BTN2A1 B30.2 domain is a homodimer, even in the absence of its extracellular and transmembrane region. [31P]-NMR experiments confirmed that HMBPP binds to BTN3A1 but not BTN2A1, and binding abrogates signals from both phosphorus atoms. Furthermore, the BTN2A1 L325G mutation but not the L318G mutation prevents both homodimerization of BTN2A1 internal domain constructs in size exclusion chromatography (and NMR) experiments and their binding to HMBPP-bound BTN3A1 in isothermal titration calorimetry experiments. Together, these findings support the importance of homodimerization within the BTN2A1 internal domain for phospho-Ag detection.

Induction of AmpC-Mediated ß-Lactam Resistance Requires a Single Lytic Transglycosylase in Agrobacterium tumefaciens.

The remarkable ability of Agrobacterium tumefaciens to transfer DNA to plant cells has allowed the generation of important transgenic crops. One challenge of A. tumefaciens-mediated transformation is eliminating the bacteria after plant transformation to prevent detrimental effects to plants and the release of engineered bacteria to the environment. Here, we use a reverse-genetics approach to identify genes involved in ampicillin resistance, with the goal of utilizing these antibiotic-sensitive strains for plant transformations. We show that treating A. tumefaciens C58 with ampicillin led to increased ß-lactamase production, a response dependent on the broad-spectrum ß-lactamase AmpC and its transcription factor, AmpR. Loss of the putative ampD orthologue atu2113 led to constitutive production of AmpC-dependent ß-lactamase activity and ampicillin resistance. Finally, one cell wall remodeling enzyme, MltB3, was necessary for the AmpC-dependent ß-lactamase activity, and its loss elicited ampicillin and carbenicillin sensitivity in the A. tumefaciens C58 and GV3101 strains. Furthermore, GV3101 ΔmltB3 transforms plants with efficiency comparable to that of the wild type but can be cleared with sublethal concentrations of ampicillin. The functional characterization of the genes involved in the inducible ampicillin resistance pathway of A. tumefaciens constitutes a major step forward in efforts to reduce the intrinsic antibiotic resistance of this bacterium. IMPORTANCE Agrobacterium tumefaciens, a significant biotechnological tool for production of transgenic plant lines, is highly resistant to a wide variety of antibiotics, posing challenges for various applications. One challenge is the efficient elimination of A. tumefaciens from transformed plant tissue without using levels of antibiotics that are toxic to the plants. Here, we present the functional characterization of genes involved in ß-lactam resistance in A. tumefaciens. Knowledge about proteins that promote or inhibit ß-lactam resistance will enable the development of strains to improve the efficiency of Agrobacterium-mediated plant genetic transformations. Effective removal of Agrobacterium from transformed plant tissue has the potential to maximize crop yield and food production, improving the outlook for global food security.

d-canavanine affects peptidoglycan structure, morphogenesis and fitness in Rhizobiales.

The bacterial cell wall is made of peptidoglycan (PG), a polymer that is essential for maintenance of cell shape and survival. Many bacteria alter their PG chemistry as a strategy to adapt their cell wall to external challenges. Therefore, identifying these environmental cues is important to better understand the interplay between microbes and their habitat. Here, we used the soil bacterium Pseudomonas putida to uncover cell wall modulators from plant extracts and found canavanine (CAN), a non-proteinogenic amino acid. We demonstrated that cell wall chemical editing by CAN is licensed by P. putida BSAR, a broad-spectrum racemase which catalyses production of dl-CAN from l-CAN, which is produced by many legumes. Importantly, d-CAN diffuses to the extracellular milieu thereby having a potential impact on other organisms inhabiting the same niche. Our results show that d-CAN alters dramatically the PG structure of Rhizobiales (e.g., Agrobacterium tumefaciens, Sinorhizobium meliloti), impairing PG crosslinkage and cell division. Using A. tumefaciens, we demonstrated that the detrimental effect of d-CAN is suppressed by a single amino acid substitution in the cell division PG transpeptidase penicillin binding protein 3a. Collectively, this work highlights the role of amino acid racemization in cell wall chemical editing and fitness.

Repeat associated mechanisms of genome evolution and function revealed by the Mus caroli and Mus pahari genomes.

Understanding the mechanisms driving lineage-specific evolution in both primates and rodents has been hindered by the lack of sister clades with a similar phylogenetic structure having high-quality genome assemblies. Here, we have created chromosome-level assemblies of the Mus caroli and Mus pahari genomes. Together with the Mus musculus and Rattus norvegicus genomes, this set of rodent genomes is similar in divergence times to the Hominidae (human-chimpanzee-gorilla-orangutan). By comparing the evolutionary dynamics between the Muridae and Hominidae, we identified punctate events of chromosome reshuffling that shaped the ancestral karyotype of Mus musculus and Mus caroli between 3 and 6 million yr ago, but that are absent in the Hominidae. Hominidae show between four- and sevenfold lower rates of nucleotide change and feature turnover in both neutral and functional sequences, suggesting an underlying coherence to the Muridae acceleration. Our system of matched, high-quality genome assemblies revealed how specific classes of repeats can play lineage-specific roles in related species. Recent LINE activity has remodeled protein-coding loci to a greater extent across the Muridae than the Hominidae, with functional consequences at the species level such as reproductive isolation. Furthermore, we charted a Muridae-specific retrotransposon expansion at unprecedented resolution, revealing how a single nucleotide mutation transformed a specific SINE element into an active CTCF binding site carrier specifically in Mus caroli, which resulted in thousands of novel, species-specific CTCF binding sites. Our results show that the comparison of matched phylogenetic sets of genomes will be an increasingly powerful strategy for understanding mammalian biology.

Functional characterization of a subtilisin-like serine protease from Vibrio cholerae.

Vibrio cholerae, the causative agent of the human diarrheal disease cholera, exports numerous enzymes that facilitate its adaptation to both intestinal and aquatic niches. These secreted enzymes can mediate nutrient acquisition, biofilm assembly, and V. cholerae interactions with its host. We recently identified a V. cholerae-secreted serine protease, IvaP, that is active in V. cholerae-infected rabbits and human choleric stool. IvaP alters the activity of several host and pathogen enzymes in the gut and, along with other secreted V. cholerae proteases, decreases binding of intelectin, an intestinal carbohydrate-binding protein, to V. cholerae in vivo IvaP bears homology to subtilisin-like enzymes, a large family of serine proteases primarily comprised of secreted endopeptidases. Following secretion, IvaP is cleaved at least three times to yield a truncated enzyme with serine hydrolase activity, yet little is known about the mechanism of extracellular maturation. Here, we show that IvaP maturation requires a series of sequential N- and C-terminal cleavage events congruent with the enzyme's mosaic protein domain structure. Using a catalytically inactive reporter protein, we determined that IvaP can be partially processed in trans, but intramolecular proteolysis is most likely required to generate the mature enzyme. Unlike many other subtilisin-like enzymes, the IvaP cleavage pattern is consistent with stepwise processing of the N-terminal propeptide, which could temporarily inhibit, and be cleaved by, the purified enzyme. Furthermore, IvaP was able to cleave purified intelectin, which inhibited intelectin binding to V. cholerae These results suggest that IvaP plays a role in modulating intelectin-V. cholerae interactions.

Agrobacterium tumefaciens divisome proteins regulate the transition from polar growth to cell division.

The mechanisms that restrict peptidoglycan biosynthesis to the pole during elongation and re-direct peptidoglycan biosynthesis to mid-cell during cell division in polar-growing Alphaproteobacteria are largely unknown. Here, we explore the role of early division proteins of Agrobacterium tumefaciens including three FtsZ homologs, FtsA and FtsW in the transition from polar growth to mid-cell growth and ultimately cell division. Although two of the three FtsZ homologs localize to mid-cell, exhibit GTPase activity and form co-polymers, only one, FtsZAT , is required for cell division. We find that FtsZAT is required not only for constriction and cell separation, but also for initiation of peptidoglycan synthesis at mid-cell and cessation of polar peptidoglycan biosynthesis. Depletion of FtsZAT in A. tumefaciens causes a striking phenotype: cells are extensively branched and accumulate growth active poles through tip splitting events. When cell division is blocked at a later stage by depletion of FtsA or FtsW, polar growth is terminated and ectopic growth poles emerge from mid-cell. Overall, this work suggests that A. tumefaciens FtsZ makes distinct contributions to the regulation of polar growth and cell division.

Activation of a cryptic 5' splice site reverses the impact of pathogenic splice site mutations in the spinal muscular atrophy gene.

Spinal muscular atrophy (SMA) is caused by deletions or mutations of the Survival Motor Neuron 1 (SMN1) gene coupled with predominant skipping of SMN2 exon 7. The only approved SMA treatment is an antisense oligonucleotide that targets the intronic splicing silencer N1 (ISS-N1), located downstream of the 5' splice site (5'ss) of exon 7. Here, we describe a novel approach to exon 7 splicing modulation through activation of a cryptic 5'ss (Cr1). We discovered the activation of Cr1 in transcripts derived from SMN1 that carries a pathogenic G-to-C mutation at the first position (G1C) of intron 7. We show that Cr1-activating engineered U1 snRNAs (eU1s) have the unique ability to reprogram pre-mRNA splicing and restore exon 7 inclusion in SMN1 carrying a broad spectrum of pathogenic mutations at both the 3'ss and 5'ss of the exon 7. Employing a splicing-coupled translation reporter, we demonstrate that mRNAs generated by an eU1-induced activation of Cr1 produce full-length SMN. Our findings underscore a wider role for U1 snRNP in splicing regulation and reveal a novel approach for the restoration of SMN exon 7 inclusion for a potential therapy of SMA.

Gender-Specific Amelioration of SMA Phenotype upon Disruption of a Deep Intronic Structure by an Oligonucleotide.

Spinal muscular atrophy (SMA), the leading genetic disease of children, is caused by low levels of survival motor neuron (SMN) protein. Here, we employ A15/283, an antisense oligonucleotide targeting a deep intronic sequence/structure, to examine the impact of restoration of SMN in a mild SMA mouse model. We show gender-specific amelioration of tail necrosis upon subcutaneous administrations of A15/283 into SMA mice at postnatal days 1 and 3. We also demonstrate that a modest increase in SMN due to early administrations of A15/283 dramatically improves testicular development and spermatogenesis. Our results reveal near total correction of expression of several genes in adult testis upon temporary increase in SMN during early postnatal development. This is the first demonstration of in vivo efficacy of an antisense oligonucleotide targeting a deep intronic sequence/structure. This is also the first report of gender-specific amelioration of SMA pathology upon a modest peripheral increase of SMN.

Absence of the Polar Organizing Protein PopZ Results in Reduced and Asymmetric Cell Division in Agrobacterium tumefaciens.

Agrobacterium tumefaciens is a rod-shaped bacterium that grows by polar insertion of new peptidoglycan during cell elongation. As the cell cycle progresses, peptidoglycan synthesis at the pole ceases prior to insertion of new peptidoglycan at midcell to enable cell division. The A. tumefaciens homolog of the Caulobacter crescentus polar organelle development protein PopZ has been identified as a growth pole marker and a candidate polar growth-promoting factor. Here, we characterize the function of PopZ in cell growth and division of A. tumefaciens Consistent with previous observations, we observe that PopZ localizes specifically to the growth pole in wild-type cells. Despite the striking localization pattern of PopZ, we find the absence of the protein does not impair polar elongation or cause major changes in the peptidoglycan composition. Instead, we observe an atypical cell length distribution, including minicells, elongated cells, and cells with ectopic poles. Most minicells lack DNA, suggesting a defect in chromosome segregation. Furthermore, the canonical cell division proteins FtsZ and FtsA are misplaced, leading to asymmetric sites of cell constriction. Together, these data suggest that PopZ plays an important role in the regulation of chromosome segregation and cell division.IMPORTANCEA. tumefaciens is a bacterial plant pathogen and a natural genetic engineer. However, very little is known about the spatial and temporal regulation of cell wall biogenesis that leads to polar growth in this bacterium. Understanding the molecular basis of A. tumefaciens growth may allow for the development of innovations to prevent disease or to promote growth during biotechnology applications. Finally, since many closely related plant and animal pathogens exhibit polar growth, discoveries in A. tumefaciens may be broadly applicable for devising antimicrobial strategies.

Mini-Tn7 Insertion in an Artificial attTn7 Site Enables Depletion of the Essential Master Regulator CtrA in the Phytopathogen Agrobacterium tumefaciens.

UNLABELLED: Mechanistic studies of many processes in Agrobacterium tumefaciens have been hampered by a lack of genetic tools for characterization of essential genes. In this study, we used a Tn7-based method for inducible control of transcription from an engineered site on the chromosome. We demonstrate that this method enables tighter control of inducible promoters than plasmid-based systems and can be used for depletion studies. The method enables the construction of depletion strains to characterize the roles of essential genes in A. tumefaciens Here, we used the strategy to deplete the alphaproteobacterial master regulator CtrA and found that depletion of this essential gene results in dramatic rounding of cells, which become nonviable. IMPORTANCE: Agrobacterium tumefaciens is a bacterial plant pathogen and natural genetic engineer. Thus, studies of essential processes, including cell cycle progression, DNA replication and segregation, cell growth, and division, may provide insights for limiting disease or improving biotechnology applications.

Strategies for maximizing ATP supply in the microsporidian Encephalitozoon cuniculi: direct binding of mitochondria to the parasitophorous vacuole and clustering of the mitochondrial porin VDAC.

Microsporidia are obligate intracellular parasites with extremely reduced genomes and a dependence on host-derived ATP. The microsporidium Encephalitozoon cuniculi proliferates within a membranous vacuole and we investigated how the ATP supply is optimized at the vacuole-host interface. Using spatial EM quantification (stereology), we found a single layer of mitochondria coating substantial proportions of the parasitophorous vacuole. Mitochondrial binding occurred preferentially over the vegetative 'meront' stages of the parasite, which bulged into the cytoplasm, thereby increasing the membrane surface available for mitochondrial interaction. In a broken cell system mitochondrial binding was maintained and was typified by electron dense structures (< 10 nm long) bridging between outer mitochondrial and vacuole membranes. In broken cells mitochondrial binding was sensitive to a range of protease treatments. The function of directly bound mitochondria, as measured by the membrane potential sensitive dye JC-1, was indistinguishable from other mitochondria in the cell although there was a generalized depression of the membrane potential in infected cells. Finally, quantitative immuno-EM revealed that the ATP-delivering mitochondrial porin, VDAC, was concentrated atthe mitochondria-vacuole interaction site. Thus E. cuniculi appears to maximize ATP supply by direct binding of mitochondria to the parasitophorous vacuole bringing this organelle within 0.020 microns of the growing vegetative form of the parasite. ATP-delivery is further enhanced by clustering of ATP transporting porins in those regions of the outer mitochondrial membrane lying closest to the parasite.

Spinal muscular atrophy: an update on therapeutic progress.

Humans have two nearly identical copies of survival motor neuron gene: SMN1 and SMN2. Deletion or mutation of SMN1 combined with the inability of SMN2 to compensate for the loss of SMN1 results in spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. SMA affects 1 in ~6000 live births, a frequency much higher than in several genetic diseases. The major known defect of SMN2 is the predominant exon 7 skipping that leads to production of a truncated protein (SMNΔ7), which is unstable. Therefore, SMA has emerged as a model genetic disorder in which almost the entire disease population could be linked to the aberrant splicing of a single exon (i.e. SMN2 exon 7). Diverse treatment strategies aimed at improving the function of SMN2 have been envisioned. These strategies include, but are not limited to, manipulation of transcription, correction of aberrant splicing and stabilization of mRNA, SMN and SMNΔ7. This review summarizes up to date progress and promise of various in vivo studies reported for the treatment of SMA.

Canonical transient receptor channel 5 (TRPC5) and TRPC1/4 contribute to seizure and excitotoxicity by distinct cellular mechanisms.

Seizures are the manifestation of highly synchronized burst firing of a large population of cortical neurons. Epileptiform bursts with an underlying plateau potential in neurons are a cellular correlate of seizures. Emerging evidence suggests that the plateau potential is mediated by neuronal canonical transient receptor potential (TRPC) channels composed of members of the TRPC1/4/5 subgroup. We previously showed that TRPC1/4 double-knockout (DKO) mice lack epileptiform bursting in lateral septal neurons and exhibit reduced seizure-induced neuronal cell death, but surprisingly have unaltered pilocarpine-induced seizures. Here, we report that TRPC5 knockout (KO) mice exhibit both significantly reduced seizures and minimal seizure-induced neuronal cell death in the hippocampus. Interestingly, epileptiform bursting induced by agonists for metabotropic glutamate receptors in the hippocampal CA1 area is unaltered in TRPC5 KO mice, but is abolished in TRPC1 KO and TRPC1/4 DKO mice. In contrast, long-term potentiation is greatly reduced in TRPC5 KO mice, but is normal in TRPC1 KO and TRPC1/4 DKO mice. The distinct changes from these knockouts suggest that TRPC5 and TRPC1/4 contribute to seizure and excitotoxicity by distinct cellular mechanisms. Furthermore, the reduced seizure and excitotoxicity and normal spatial learning exhibited in TRPC5 KO mice suggest that TRPC5 is a promising novel molecular target for new therapy.

A Group-Based, Videoconference-Delivered Physical Activity Program for Cancer Survivors.

Introduction/Purpose: Virtually supervised, group-based exercise presents an innovative way to expand the reach of exercise-oncology programs and help cancer survivors increase physical activity (PA) and connect with other participants. This study examined the feasibility, acceptability, and preliminary effects of a group-based PA program delivered exclusively using videoconferencing software. Methods: This study used a single-group pre-post design. The 8-wk program consisted of aerobic and resistance exercise sessions once per week and three PA behavior change discussion sessions in groups of four to six. Feasibility was determined by enrollment, retention, safety, and adherence. Postprogram surveys evaluated acceptability using a Likert scale and open-ended responses. Changes in PA (Godin Leisure-Time Exercise Questionnaire), quality of life (QOL; Functional Assessment of Cancer Therapy- General), and upper and lower body muscular endurance (bicep curl and sit-to-stand test) were also evaluated. Results: Enrollment was feasible (n = 61 of 65 who expressed interest in the program), and retention (86.9%) and adherence (88% for exercise, 91% for discussion) were high; no adverse events were reported. Participants (mean age, 59.9 ± 10.1 yr; 96.2% female; 64.2% ovarian cancer, 28.3% breast cancer, 7.5% other cancer) reported they enjoyed the program (median, 7 of 7), and videoconferencing software was easy to use and had good video and audio quality (median, 5 of 5). From preprogram to postprogram, participants increased their weekly minutes of aerobic (mean (SD) change, 82.4 (144.2)) and resistance (mean (SD) change, 31.9 (42.7)) PA; sit-to-stand (mean (SD) change, 1.4 (3.9)) and bicep curl (mean (SD) change, 5.3 (6.8)) repetitions; and emotional (mean (SD) change, 0.82 (2.3) points), functional (mean (SD) change, 1.2 (3.6) points), and total QOL (mean (SD) change, 3 (7.9) points; all P < 0.05). Conclusions: A group-based PA program delivered using videoconference technology is feasible and acceptable for cancer survivors, and may increase PA and improve physical fitness and some aspects of QOL. A larger, controlled intervention is needed to determine efficacy, as well as pragmatic studies to directly compare this approach with conventional strategies (i.e., face-to-face programs).

Embelin and levodopa combination therapy for improved Parkinson's disease treatment.

Parkinson's disease (PD), a progressive neurodegenerative disorder, affects dopaminergic neurons. Oxidative stress and gut damage play critical roles in PD pathogenesis. Inhibition of oxidative stress and gut damage can prevent neuronal death and delay PD progression. The objective of this study was to evaluate the therapeutic effect of embelin or the combination with levodopa (LD) in a rotenone-induced PD mouse model. At the end of experimentation, the mice were sacrificed and the midbrain was used to evaluate various biochemical parameters, such as nitric oxide, peroxynitrite, urea, and lipid peroxidation. In the substantia nigra (midbrain), tyrosine hydroxylase (TH) expression was examined by immunohistochemistry, and Nurr1 expression was evaluated by western blotting. Gut histopathology was evaluated on tissue sections stained with hematoxylin and eosin. In silico molecular docking studies of embelin and α-synuclein (α-syn) fibrils were also performed. Embelin alone or in combination with LD ameliorated oxidative stress and gut damage. TH and Nurr1 protein levels were also significantly restored. Docking studies confirmed the affinity of embelin toward α-syn. Taken together, embelin could be a promising drug for the treatment of PD, especially when combined with LD.

Exploring synergy and its role in antimicrobial peptide biology.

Antimicrobial peptides will be an essential component in combating the escalating issue of antibiotic resistance. Identifying synergistic combinations of two or more substances will increase the value of these peptides further. Several potential pitfalls in conducting synergy testing with peptides are discussed in detail. As case studies, we describe observations of AMP synergy with peptides, antibiotics, and metal ions as well as some of the mechanistic details that have been uncovered. The Bliss and Loewe models for synergy are presented prior to recommending protocols for conducting checkerboard, minimal inhibitory concentration, and time-kill assays. Establishing mechanisms of action and exploring the potential for resistance will be crucial to translate these studies into the clinic.

Surgical Management of Osteochondral Defects of the Knee: An Educational Review.

PURPOSE OF REVIEW: Numerous surgical techniques are available to treat osteochondral defects of the knee. The aim of this review is to analyse these procedures, including their methodology, outcomes and limitations, to create a treatment algorithm for optimal management. RECENT FINDINGS: Osteochondral defects of the knee significantly alter the biomechanics of the joint. This can cause symptomatic and functional impairment as well as considerable risk of progressive joint degeneration. Surgical interventions aim to restore a congruent, durable joint surface providing symptomatic relief and reducing the risk of early arthritic changes. These methods include fixation, chondroplasty, microfracture, autologous matrix-induced chondrogenesis, autograft transplants, allograft transplants and autologous chondrocyte implantation. There is currently much debate as to which of these methods provides optimal treatment of osteochondral defects. The overall evidence supports the use of each technique depending on the individual characteristics of the lesion. New technologies provide exciting prospects; however, long-term outcomes for these are not yet available.

Iliopsoas pathology after total hip arthroplasty: a young person's complication.

AIMS: Iliopsoas pathology is a relatively uncommon cause of pain following total hip arthroplasty (THA), typically presenting with symptoms of groin pain on active flexion and/or extension of the hip. A variety of conservative and surgical treatment options have been reported. In this retrospective cohort study, we report the incidence of iliopsoas pathology and treatment outcomes. METHODS: A retrospective review of 1,000 patients who underwent THA over a five-year period was conducted, to determine the incidence of patients diagnosed with iliopsoas pathology. Outcome following non-surgical and surgical management was assessed. RESULTS: In all, 24 patients were diagnosed as having developed symptomatic iliopsoas pathology giving an incidence of 2.4%. While the mean age for receiving a THA was 65 years, the mean age for developing iliopsoas pathology was 54 years (28 to 67). Younger patients and those receiving THA for conditions other than primary osteoarthritis were at a higher risk of developing this complication. Ultrasound-guided steroid injection/physiotherapy resulted in complete resolution of symptoms in 61% of cases, partial resolution in 13%, and no benefit in 26%. Eight out of 24 patients (who initially responded to injection) subsequently underwent surgical intervention including tenotomy (n = 7) and revision of the acetabular component (n = 1). CONCLUSION: This is the largest case series to estimate the incidence of iliopsoas pathology to date. There is a higher incidence of this condition in younger patients, possibly due to the differing surgical indications. Arthoplasty for Perthes' disease or developmental dysplasia of the hip (DDH) often results in leg length and horizontal offset being increased. This, in turn, may increase tension on the iliopsoas tendon, possibly resulting in a higher risk of psoas irritation. Image-guided steroid injection is a low-risk, relatively effective treatment. In refractory cases, tendon release may be considered. Patients should be counselled of the risk of persisting groin pain when undergoing THA. Cite this article: Bone Joint J 2021;103-B(2):305-308.

Abnormal post-translational and extracellular processing of brevican in plaque-bearing mice over-expressing APPsw.

Aggregation of amyloid-beta (Abeta) in the forebrain of Alzheimer's disease (AD) subjects may disturb the molecular organization of the extracellular microenvironment that modulates neural and synaptic plasticity. Proteoglycans are major components of this extracellular environment. To test the hypothesis that Abeta, or another amyloid precursor protein (APP) dependent mechanism modifies the accumulation and/or turnover of extracellular proteoglycans, we examined whether the expression and processing of brevican, an abundant extracellular, chondroitin sulfate (CS)-bearing proteoglycan, were altered in brains of Abeta-depositing transgenic mice (APPsw - APP gene bearing the Swedish mutation) as a model of AD. The molecular size of CS chains attached to brevican was smaller in hippocampal tissue from APPsw mice bearing Abeta deposits compared to non-transgenic mice, likely because of changes in the CS chains. Also, the abundance of the major proteolytic fragment of brevican was markedly diminished in extracts from several telencephalic regions of APPsw mice compared to non-transgenic mice, yet these immunoreactive fragments appeared to accumulate adjacent to the plaque edge. These results suggest that Abeta or APP exert inhibitory effects on proteolytic cleavage mechanisms responsible for synthesis and turnover of proteoglycans. As proteoglycans stabilize synaptic structure and inhibit molecular plasticity, defective brevican processing observed in Abeta-bearing mice and potentially end-stage human AD, may contribute to deficient neural plasticity.