Understanding large scale sequencing datasets through changes to protein folding.

The expansion of high-quality, low-cost sequencing has created an enormous opportunity to understand how genetic variants alter cellular behaviour in disease. The high diversity of mutations observed has however drawn a spotlight onto the need for predictive modelling of mutational effects on phenotype from variants of uncertain significance. This is particularly important in the clinic due to the potential value in guiding clinical diagnosis and patient treatment. Recent computational modelling has highlighted the importance of mutation induced protein misfolding as a common mechanism for loss of protein or domain function, aided by developments in methods that make large computational screens tractable. Here we review recent applications of this approach to different genes, and how they have enabled and supported subsequent studies. We further discuss developments in the approach and the role for the approach in light of increasingly high throughput experimental approaches.

A case report of lactobacillus bacteremia in a patient on chronic parenteral nutrition.

BACKGROUND AND AIMS: Short bowel syndrome is a malabsorption disorder typically caused by the physical loss of a portion of the intestine, whereafter the body is unable to adequately absorb nutrients, fluids, and electrolytes. Many patients with short bowel syndrome are reliant on home parenteral nutrition through a tunneled or peripherally inserted central catheter to ensure sufficient hydration and nutrition. Central venous catheters are a nidus for bacteria, and patients are at risk for infections associated with high levels of morbidity and mortality. Lactobacillus is a ubiquitous microorganism that most frequently colonizes mucosal surfaces such as the gastrointestinal tract. Lactobacillus bacteremia is rare, with limited occurrence in current medical literature. METHODS: Our patient is a 60-year-old female with a past medical history significant for multiple abdominal surgeries resulting in short bowel syndrome, with subsequent dependence on home parenteral nutrition via peripherally inserted central catheter. She had type III chronic intestinal failure, category D2, and stage 1 moderate malnutrition. She was originally admitted to the hospital for a presumed pulmonary embolism and was found to have a deep vein thrombosis in the setting of her peripherally inserted central catheter. On admission her abdominal exam was unremarkable, she denied abdominal pain, and her only gastrointestinal complaint was chronic stable diarrhea. During the hospitalization she developed severe left lower quadrant abdominal pain and noted decreased frequency of her bowel movements. A computed tomography scan of her abdomen revealed chronic stable intestinal distension and was concerning for obstruction. Clinically she remained without symptoms of acute obstruction or ileus. During the admission she became febrile, with blood cultures from her peripherally inserted central catheter and peripheral IV growing out gram negative rods determined to be lactobacillus bacteremia. The infectious disease team recommended removal of her peripherally inserted central catheter given their concern for a line infection. RESULTS: The patient was treated with broad-spectrum antibiotics, did well clinically, and was ultimately discharged following reinsertion of her peripherally inserted central catheter after negative repeat blood cultures. Though she initially did well in the outpatient setting, she ultimately passed away ten months later after re-presenting to the hospital in septic shock, secondary to bowel ischemia and suspected fungemia of her peripherally inserted central catheter. CONCLUSIONS: In this case report, we describe an unusual case of a patient with short bowel syndrome on chronic parenteral nutrition who developed catheter-associated lactobacillus bacteremia - the first reported case in an adult patient on parenteral nutrition.

Large-scale computational modelling of the M1 and M2 synovial macrophages in rheumatoid arthritis.

Macrophages play an essential role in rheumatoid arthritis. Depending on their phenotype (M1 or M2), they can play a role in the initiation or resolution of inflammation. The M1/M2 ratio in rheumatoid arthritis is higher than in healthy controls. Despite this, no treatment targeting specifically macrophages is currently used in clinics. Thus, devising strategies to selectively deplete proinflammatory macrophages and promote anti-inflammatory macrophages could be a promising therapeutic approach. State-of-the-art molecular interaction maps of M1 and M2 macrophages in rheumatoid arthritis are available and represent a dense source of knowledge; however, these maps remain limited by their static nature. Discrete dynamic modelling can be employed to study the emergent behaviours of these systems. Nevertheless, handling such large-scale models is challenging. Due to their massive size, it is computationally demanding to identify biologically relevant states in a cell- and disease-specific context. In this work, we developed an efficient computational framework that converts molecular interaction maps into Boolean models using the CaSQ tool. Next, we used a newly developed version of the BMA tool deployed to a high-performance computing cluster to identify the models' steady states. The identified attractors are then validated using gene expression data sets and prior knowledge. We successfully applied our framework to generate and calibrate the M1 and M2 macrophage Boolean models for rheumatoid arthritis. Using KO simulations, we identified NFkB, JAK1/JAK2, and ERK1/Notch1 as potential targets that could selectively suppress proinflammatory macrophages and GSK3B as a promising target that could promote anti-inflammatory macrophages in rheumatoid arthritis.

Interpreting the effect of mutations to protein binding sites from large-scale genomic screens.

Predicting the functionality of missense mutations is extremely difficult. Large-scale genomic screens are commonly performed to identify mutational correlates or drivers of disease and treatment resistance, but interpretation of how these mutations impact protein function is limited. One such consequence of mutations to a protein is to impact its ability to bind and interact with partners or small molecules such as ATP, thereby modulating its function. Multiple methods exist for predicting the impact of a single mutation on protein-protein binding energy, but it is difficult in the context of a genomic screen to understand if these mutations with large impacts on binding are more common than statistically expected. We present a methodology for taking mutational data from large-scale genomic screens and generating functional and statistical insights into their role in the binding of proteins both with each other and their small molecule ligands. This allows a quantitative and statistical analysis to determine whether mutations impacting protein binding or ligand interactions are occurring more or less frequently than expected by chance. We achieve this by calculating the potential impact of any possible mutation and comparing an expected distribution to the observed mutations. This method is applied to examples demonstrating its ability to interpret mutations involved in protein-protein binding, protein-DNA interactions, and the evolution of therapeutic resistance.

Hydrocephalus in prematurity: does valve choice make a difference?

PURPOSE: Extremely premature neonates diagnosed with post-haemorrhagic hydrocephalus (PHH) are recognised to have particularly poor outcomes. This study assessed the impact of a number of variables on outcomes in this cohort, in particular the choice of shunt valve mechanism. METHODS: Electronic case notes were retrospectively reviewed of all premature neonates admitted to our centre for management of hydrocephalus between 2012 and 2021. Data included (i) gestational age, (ii) birth weight, (iii) hydrocephalus aetiology, (iv) surgical intervention, (v) shunt system, (vi) 'surgical burden' and (vii) wound failure and infection rate. Data was handled in Microsoft Excel and statistical analysis performed in SPSS v27.0 RESULTS: N = 53 premature hydrocephalic patients were identified (n = 28 (52.8%) female). Median gestational age at birth was 27 weeks (range: 23-36 + 6 weeks), with n = 35 extremely preterm patients and median birth weight of 1.9 kg (range: 0.8-3.6 kg). Total n = 99 programmable valves were implanted (n = 28 (28.3%) de novo, n = 71 (71.2%) revisions); n = 28 (28.3%) underwent n ≥ 1 pressure alterations, after which n = 21 (75%) patients had symptoms improve. In n = 8 patients exchanged from fixed to programmable valves, a mean reduction of 1.9 revisions per patient after exchange was observed (95%CI: 0.36-3.39, p = 0.02). Mean overall shunt survival was 39.5 weeks (95%CI: 30.6-48.5); 33.2 weeks (95%CI: 25.2-41.1) in programmable valves and 35.1 weeks (95%CI: 19.5-50.6) in fixed pressure (p = 0.22) with 12-month survival rates of 25.7% and 24.7%, respectively (p = 0.22). Shorter de novo shunt survival was associated with higher operation count overall (Pearson's R: - 0.54, 95%CI: - 0.72 to - 0.29, p < 0.01). Wound failure, gestational age and birth weight were significantly associated with shorter de novo shunt survival in a Cox regression proportional hazards model; gestational age had the greatest impact on shunt survival (Exp(B): 0.71, 95%CI: 0.63-0.81, p < 0.01). CONCLUSION: Hydrocephalus is especially challenging in extreme prematurity, with a shorter de novo shunt survival associated with higher number of future revisions. Programmable valves provide flexibility with regard to pressure setting, with the potential for fewer shunt revisions in this complex cohort.

A tailored approach to the management of post-haemorrhagic hydrocephalus.

PURPOSE: Neuro-endoscopic lavage (NEL) is an increasingly popular intervention for intraventricular haemorrhage (IVH) and post-haemorrhagic hydrocephalus (PHH), with considerable variation in technique dependent on clinician and clinical circumstances. Whilst efforts to standardise the technique are ongoing, this work describes a tertiary centre experience utilising NEL, highlighting potential caveats to standardisation. METHODS: A retrospective review of electronic case notes for patients undergoing temporising surgical intervention for IVH between 2012 and 2021 at our centre was performed. Data collected included (i) gestational age, (ii) aetiology of hydrocephalus, (iii) age at time of intervention, (iv) intervention performed, (v) need for permanent CSF diversion, (vi) 'surgical burden', i.e. number of procedures following primary intervention, and (vii) wound failure and infection rate. Data was handled in Microsoft Excel and statistical analysis SPSS v27.0 RESULTS: 49 neonates (n = 25 males) were included. Overall mean gestational age was 27 weeks and at intervention 35 + 3 weeks. IVH was the predominant cause of hydrocephalus (93.8%) and primary surgical interventions included insertion of a ventriculosubgaleal shunt (VSGS) in n = 41 (83.6%) patients, NEL in n = 6 (12.2%) patients and insertion of an EVD in n = 2 (4.1%). N = 9 (18.4%) patients underwent NEL at some point during the time interval reviewed; n = 4 (8.2%) received NEL monotherapy and n = 5 (10.2%) also received a VSGS. Rate of conversion to definitive CSF diversion between NEL (n = 8, 88.9%) and VSGS cohorts (n = 37, 92.5%) was not significantly different (p = 0.57), nor between NEL alone (n = 3, 75%) and NEL + VSGS (n = 5, 100%) (p = 0.44). None of the patients that underwent NEL monotherapy had any wound issues or CNS infection as a result of the initial intervention, compared to n = 3 (60%) of those that underwent NEL and implantation of VSGS (p = 0.1). CONCLUSION: Both NEL and VSGS are effective in temporising hydrocephalus in neonates, occasionally offering a definitive solution in and of themselves. The benefit of dual therapy however remains to be seen, with the addition of VSGS potentially increasing the risk of wound failure in an already vulnerable cohort.

Outcomes for sigmoid volvulus managed with and without early definitive surgery: 20-year experience in a tertiary referral centre.

BACKGROUND: Sigmoid volvulus is rare in Western countries. Patients at risk of sigmoid volvulus are often older with significant co-morbidity. Without sigmoid colectomy there is a high recurrence rate, but indications for surgery are controversial. METHODS: A retrospective observational study was conducted by reviewing clinical records of patients admitted to Waikato Hospital 1 January 2000 to 1 January 2020 with a diagnosis of sigmoid volvulus. Patient characteristics, clinical features, investigations, management, and outcomes were recorded. RESULTS: One hundred and thirty-two patients (87 male) were included with 203 volvulus episodes. Median age 76 years, median Charlson co-morbidity index (CCI) 4. Median follow-up 11 years. 44/132 (33.3%) had surgery during the index admission, two had elective surgery and the remainder had planned non-operative management. 73/132 (55.3%) had surgery at any stage. 42/86 (48.8%) patients managed non-operatively recurred; 66.7% of recurrences were within 6 months. Forty-three (32.6%) died within 12 months of index admission; 28 (21.2%) died during an admission for volvulus. On univariate analysis higher age and abnormal vital signs were associated with inpatient and 12-month mortality; higher CCI was associated with 12-month mortality. On multi-variate analysis increasing age in years was associated with increased risk of death (HR 1.089 [1.052-1.128, P < 0.001]). Normal vital signs at presentation were associated with decreased risk of death (HR 0.147 [0.065-0.334, P < 0.001]). CONCLUSION: Sigmoid colectomy should be considered at index presentation with sigmoid volvulus. Half of patients managed non-operatively recurred, with two-thirds recurring within 6 months. The mortality rate remains high for subsequent volvulus episodes.

Selective dorsal rhizotomy in non-ambulant children with cerebral palsy: a multi-center prospective study.

PURPOSE: Assess the effects of selective dorsal rhizotomy (SDR) on motor function and quality of life in children with a Gross Motor Function Classification System (GMFCS) level of IV or V (non-ambulatory). METHODS: This is a prospective, observational study in three tertiary neurosurgery units in England, UK, performing SDR on children aged 3-18 with spastic diplegic cerebral palsy, and a GMFCS level of IV or V, between 2012 and 2019. The primary outcome measure was the change in the 66-item Gross Motor Function Measure (GMFM-66) from baseline to 24 months after SDR, using a linear mixed effects model. Secondary outcomes included spasticity, bladder function, quality of life, and pain scores. RESULTS: Between 2012 and 2019, 144 children who satisfied these inclusion criteria underwent SDR. The mean age was 8.2 years. Fifty-two percent were female. Mean GMFM-66 score was available in 77 patients (53.5%) and in 39 patients (27.1%) at 24 months after SDR. The mean increase between baseline and 24 months post-SDR was 2.4 units (95% CI 1.7-3.1, p < 0.001, annual change 1.2 units). Of the 67 patients with a GMFM-66 measurement available, a documented increase in gross motor function was seen in 77.6% (n = 52). Of 101 patients with spasticity data available, mean Ashworth scale decreased after surgery (2.74 to 0.30). Of patients' pain scores, 60.7% (n = 34) improved, and 96.4% (n = 56) of patients' pain scores remained the same or improved. Bladder function improved in 30.9% of patients. CONCLUSIONS: SDR improved gross motor function and reduced pain in most patients at 24 months after surgery, although the improvement is less pronounced than in children with GMFCS levels II and III. SDR should be considered in non-ambulant patients.

Selective and brain-penetrant HCN1 inhibitors reveal links between synaptic integration, cortical function, and working memory.

Hyperpolarization-activated and cyclic-nucleotide-gated 1 (HCN1) ion channels are proposed to be critical for cognitive function through regulation of synaptic integration. However, resolving the precise role of HCN1 in neurophysiology and exploiting its therapeutic potential has been hampered by minimally selective antagonists with poor potency and limited in vivo efficiency. Using automated electrophysiology in a small-molecule library screen and chemical optimization, we identified a primary carboxamide series of potent and selective HCN1 inhibitors with a distinct mode of action. In cognition-relevant brain circuits, selective inhibition of native HCN1 produced on-target effects, including enhanced excitatory postsynaptic potential summation, while administration of a selective HCN1 inhibitor to rats recovered decrement working memory. Unlike prior non-selective HCN antagonists, selective HCN1 inhibition did not alter cardiac physiology in human atrial cardiomyocytes or in rats. Collectively, selective HCN1 inhibitors described herein unmask HCN1 as a potential target for the treatment of cognitive dysfunction in brain disorders.

SMAD4 and KCNQ3 alterations are associated with lymph node metastases in oesophageal adenocarcinoma.

Metastasis in oesophageal adenocarcinoma (OAC) is an important predictor of survival. Radiological staging is used to stage metastases in patients, and guide treatment selection, but is limited by the accuracy of the approach. Improvements in staging will lead to improved clinical decision making and patient outcomes. Sequencing studies on primary tumours and pre-cancerous tissue have revealed the mutational landscape of OAC, and increasingly cheap and widespread sequencing approaches offer the potential to improve staging assessment. In this work we present an analysis of lymph node metastases found by radiological and pathological sampling, identifying new roles of the genes SMAD4 and KCNQ3 in metastasis. Through transcriptomic analysis we find that both genes are associated with canonical Wnt pathway activity, but KCNQ3 is uniquely associated with changes in planar cell polaritiy associated with non-canonical Wnt signalling. We go on to validate our observations in KCNQ3 in cell line and xenograph systems, showing that overexpression of KCNQ3 reduces wound closure and the number of metastases observed. Our results suggest both genes as novel biomarkers of metastatic risk and offer new potential routes to drug targeting.

Production of carotenoids from aromatics and pretreated lignocellulosic biomass by Novosphingobium aromaticivorans.

IMPORTANCE: There is economic and environmental interest in generating commodity chemicals from renewable resources, such as lignocellulosic biomass, that can substitute for chemicals derived from fossil fuels. The bacterium Novosphingobium aromaticivorans is a promising microbial platform for producing commodity chemicals from lignocellulosic biomass because it can produce these from compounds in pretreated lignocellulosic biomass, which many industrial microbial catalysts cannot metabolize. Here, we show that N. aromaticivorans can be engineered to produce several valuable carotenoids. We also show that engineered N. aromaticivorans strains can produce these lipophilic chemicals concurrently with the extracellular commodity chemical 2-pyrone-4,6-dicarboxylic acid when grown in a complex liquor obtained from alkaline pretreated lignocellulosic biomass. Concurrent microbial production of valuable intra- and extracellular products can increase the economic value generated from the conversion of lignocellulosic biomass-derived compounds into commodity chemicals and facilitate the separation of water- and membrane-soluble products.

Striatum-projecting prefrontal cortex neurons support working memory maintenance.

Neurons in the medial prefrontal cortex (mPFC) are functionally linked to working memory (WM) but how distinct projection pathways contribute to WM remains unclear. Based on optical recordings, optogenetic perturbations, and pharmacological interventions in male mice, we report here that dorsomedial striatum (dmStr)-projecting mPFC neurons are essential for WM maintenance, but not encoding or retrieval, in a T-maze spatial memory task. Fiber photometry of GCaMP6m-labeled mPFC→dmStr neurons revealed strongest activity during the maintenance period, and optogenetic inhibition of these neurons impaired performance only when applied during this period. Conversely, enhancing mPFC→dmStr pathway activity-via pharmacological suppression of HCN1 or by optogenetic activation during the maintenance period-alleviated WM impairment induced by NMDA receptor blockade. Moreover, cellular-resolution miniscope imaging revealed that >50% of mPFC→dmStr neurons are active during WM maintenance and that this subpopulation is distinct from neurons active during encoding and retrieval. In all task periods, neuronal sequences were evident. Striatum-projecting mPFC neurons thus critically contribute to spatial WM maintenance.

Tools for Genetic Engineering and Gene Expression Control in Novosphingobium aromaticivorans and Rhodobacter sphaeroides.

Alphaproteobacteria have a variety of cellular and metabolic features that provide important insights into biological systems and enable biotechnologies. For example, some species are capable of converting plant biomass into valuable biofuels and bioproducts have the potential to form the backbone of the sustainable bioeconomy. Among the Alphaproteobacteria, Novosphingobium aromaticivorans, Rhodobacter sphaeroides, and Zymomonas mobilis, show particular promise as organisms that can be engineered to convert extracted plant lignin or sugars into bioproducts and biofuels. Genetic manipulation of these bacteria is needed to introduce engineered pathways and modulate expression of native genes with the goal of enhancing bioproduct output. Although recent work has expanded the genetic toolkit for Z. mobilis, N. aromaticivorans and R. sphaeroides still need facile, reliable approaches to deliver genetic payloads to the genome and to control gene expression. Here, we expand the platform of genetic tools for N. aromaticivorans and R. sphaeroides to address these issues. We demonstrate that Tn7 transposition is an effective approach for introducing engineered DNA into the chromosome of N. aromaticivorans and R. sphaeroides. We screen a synthetic promoter library to identify inducible promoters with strong, regulated activity in both organisms. Combining Tn7 integration with promoters from our library, we establish CRISPR interference systems for N. aromaticivorans and R. sphaeroides that can target essential genes and modulate engineered pathways. We anticipate that these systems will greatly facilitate both genetic engineering and gene function discovery efforts in these industrially important species and other Alphaproteobacteria.

KCNQ potassium channels modulate Wnt activity in gastro-oesophageal adenocarcinomas.

Voltage-sensitive potassium channels play an important role in controlling membrane potential and ionic homeostasis in the gut and have been implicated in gastrointestinal (GI) cancers. Through large-scale analysis of 897 patients with gastro-oesophageal adenocarcinomas (GOAs) coupled with in vitro models, we find KCNQ family genes are mutated in ∼30% of patients, and play therapeutically targetable roles in GOA cancer growth. KCNQ1 and KCNQ3 mediate the WNT pathway and MYC to increase proliferation through resultant effects on cadherin junctions. This also highlights novel roles of KCNQ3 in non-excitable tissues. We also discover that activity of KCNQ3 sensitises cancer cells to existing potassium channel inhibitors and that inhibition of KCNQ activity reduces proliferation of GOA cancer cells. These findings reveal a novel and exploitable role of potassium channels in the advancement of human cancer, and highlight that supplemental treatments for GOAs may exist through KCNQ inhibitors.

Somatic mutations in facial skin from countries of contrasting skin cancer risk.

The incidence of keratinocyte cancer (basal cell and squamous cell carcinomas of the skin) is 17-fold lower in Singapore than the UK1-3, despite Singapore receiving 2-3 times more ultraviolet (UV) radiation4,5. Aging skin contains somatic mutant clones from which such cancers develop6,7. We hypothesized that differences in keratinocyte cancer incidence may be reflected in the normal skin mutational landscape. Here we show that, compared to Singapore, aging facial skin from populations in the UK has a fourfold greater mutational burden, a predominant UV mutational signature, increased copy number aberrations and increased mutant TP53 selection. These features are shared by keratinocyte cancers from high-incidence and low-incidence populations8-13. In Singaporean skin, most mutations result from cell-intrinsic processes; mutant NOTCH1 and NOTCH2 are more strongly selected than in the UK. Aging skin in a high-incidence country has multiple features convergent with cancer that are not found in a low-risk country. These differences may reflect germline variation in UV-protective genes.

Intracranial Empyemas in the COVID-19 Era: A New Phenomenon? A Paediatric Case Series and Review of the Literature.

INTRODUCTION: We present the largest series of paediatric intracranial empyemas occurring after COVID-19 infection to date, and discuss the potential implications of the pandemic on this neurosurgical pathology. METHODS: Patients admitted to our centre between January 2016 and December 2021 with a confirmed radiological diagnosis of intracranial empyema were retrospectively reviewed, excluding non-otorhinological source cases. Patients were grouped according to onset before or after onset of the COVID-19 pandemic and COVID-19 status. A literature review of all post-COVID-19 intracranial empyemas was performed. SPSS v27 was used for statistical analysis. RESULTS: Sixteen patients were diagnosed with intracranial empyema: n = 5 prior to 2020 and n = 11 after, resulting in an average annual incidence of 0.3% prior to onset of the pandemic and 1.2% thereafter. Of those diagnosed since the pandemic, 4 (25%) were confirmed to have COVID-19 on recent PCR test. Time from COVID-19 infection until empyema diagnosis ranged from 15 days to 8 weeks. Mean age for post-COVID-19 cases was 8.5 years (range: 7-10 years) compared to 11 years in non-COVID cases (range: 3-14 years). Streptococcus intermedius was grown in all cases of post-COVID-19 empyema, and 3 of 4 (75%) post-COVID-19 cases developed cerebral sinus thromboses, compared to 3 of 12 (25%) non-COVID-19 cases. All cases were discharged home with no residual deficit. CONCLUSION: Our post-COVID-19 intracranial empyema series demonstrates a greater proportion of cerebral sinus thromboses than non-COVID-19 cases, potentially reflecting the thrombogenic effects of COVID-19. Incidence of intracranial empyema at our centre has increased since the start of the pandemic, causes of which require further investigation and multicentre collaboration.

Improvement of sensory deficits in fragile X mice by increasing cortical interneuron activity after the critical period.

Changes in the function of inhibitory interneurons (INs) during cortical development could contribute to the pathophysiology of neurodevelopmental disorders. Using all-optical in vivo approaches, we find that parvalbumin (PV) INs and their immature precursors are hypoactive and transiently decoupled from excitatory neurons in postnatal mouse somatosensory cortex (S1) of Fmr1 KO mice, a model of fragile X syndrome (FXS). This leads to a loss of parvalbumin INs (PV-INs) in both mice and humans with FXS. Increasing the activity of future PV-INs in neonatal Fmr1 KO mice restores PV-IN density and ameliorates transcriptional dysregulation in S1, but not circuit dysfunction. Critically, administering an allosteric modulator of Kv3.1 channels after the S1 critical period does rescue circuit dynamics and tactile defensiveness. Symptoms in FXS and related disorders could be mitigated by targeting PV-INs.

Mutations observed in somatic evolution reveal underlying gene mechanisms.

Highly sensitive DNA sequencing techniques have allowed the discovery of large numbers of somatic mutations in normal tissues. Some mutations confer a competitive advantage over wild-type cells, generating expanding clones that spread through the tissue. Competition between mutant clones leads to selection. This process can be considered a large scale, in vivo screen for mutations increasing cell fitness. It follows that somatic missense mutations may offer new insights into the relationship between protein structure, function and cell fitness. We present a flexible statistical method for exploring the selection of structural features in data sets of somatic mutants. We show how this approach can evidence selection of specific structural features in key drivers in aged tissues. Finally, we show how drivers may be classified as fitness-enhancing and fitness-suppressing through different patterns of mutation enrichment. This method offers a route to understanding the mechanism of protein function through in vivo mutant selection.

Visual Evoked Potentials as an Early-Stage Biomarker in the rTg4510 Tauopathy Mouse Model.

BACKGROUND: Tauopathies such as Alzheimer's disease (AD) and frontotemporal dementia (FTD) are characterized by formation of neurofibrillary tangles consisting of hyperphosphorylated tau protein. Early pathophysiological and functional changes related to neurofibrillary tangles formation are considered to occur prior to extensive neurodegeneration. Hyperphosphorylated tau has been detected in postmortem retinas of AD and FTD patients, and the visual pathway is an easily accessible system in a clinical setting. Hence, assessment of the visual function may offer the potential to detect consequences of early tau pathology in patients. OBJECTIVE: The aim of this study was to evaluate visual function in a tauopathy mouse model in relation to tau hyperphosphorylation and neurodegeneration. METHODS: In this study we explored the association between the visual system and functional consequences of tau pathology progression using a tauopathy rTg4510 mouse model. To this end, we recorded full-field electroretinography and visual evoked potentials in anesthetized and awake states at different ages. RESULTS: While retinal function remained mostly intact within all the age groups investigated, we detected significant changes in amplitudes of visual evoked potential responses in young rTg4510 mice exhibiting early tau pathology prior to neurodegeneration. These functional alterations in the visual cortex were positively correlated with pathological tau levels. CONCLUSION: Our findings suggest that visual processing could be useful as a novel electrophysiological biomarker for early stages of tauopathy.