Plexin-semaphorin signalling modifies neuromuscular defects in a Drosophila model of peripheral neuropathy

Dominant mutations in GARS, encoding the ubiquitous enzyme glycyl-tRNA synthetase (GlyRS), cause peripheral nerve degeneration and Charcot-Marie-Tooth disease type 2D (CMT2D). This genetic disorder exemplifies a recurring paradigm in neurodegeneration, in which mutations in essential genes cause selective degeneration of the nervous system. Recent evidence suggests that the mechanism underlying CMT2D involves extracellular neomorphic binding of mutant GlyRS to neuronally-expressed proteins. Consistent with this, our previous studies indicate a non-cell autonomous mechanism, whereby mutant GlyRS is secreted and interacts with the neuromuscular junction (NMJ). In this Drosophila model for CMT2D, we have previously shown that mutant gars expression decreases viability and larval motor function, and causes a concurrent build-up of mutant GlyRS at the larval neuromuscular presynapse. Here, we report additional phenotypes that closely mimic the axonal branching defects of Drosophila plexin transmembrane receptor mutants, implying interference of plexin signaling in gars mutants. Individual dosage reduction of two Drosophila Plexins, plexin A (plexA) and B (plexB) enhances and represses the viability and larval motor defects caused by mutant GlyRS, respectively. However, we find plexB levels, but not plexA levels, modify mutant GlyRS association with the presynaptic membrane. Furthermore, increasing availability of the plexB ligand, Semaphorin-2a (Sema2a), alleviates the pathology and the build-up of mutant GlyRS, suggesting competition for plexB binding may be occurring between these two ligands. This toxic gain-of-function and subversion of neurodevelopmental processes indicate that signaling pathways governing axonal guidance could be integral to neuropathology and may underlie the non-cell autonomous CMT2D mechanism

Hearing Benefit in Middle Ear Reconstructive Surgery: A Comparative Study of the Current Methods

INTRODUCTION: Discharging ear and deafness are perpetual source of misery to humankind. Chronic suppurative otitis media is found to be the single major cause of conductive deafness manifesting in 66.3% of cases. The other causes being trauma, otosclerosis, congenital malformations, neoplastic causes etc. Auditory sensation is one of the vital sensations for existence. Deafness upsets the tranquility of life. When such a great vital sensation is lost, life naturally loses its charm. In last 50 years, various researches have been carried out for repair of ossicular chain defects alone or those associated with tympanic membrane perforations. A number of materials have been used with varying results. Right from Hall and Rytzer of 1957 till today, several pioneers have revolutionized the outlook of ossiculoplasty. Several materials have been used for ossiculoplasty. Some of the materials are autograft/homograft ossicles, autograft/homograft cartilage, teflon, hydroxyapatite, titanium, gold, bioglass etc. The goal of otologists performing middle ear surgery to correct conductive hearing loss is to improve hearing as well as to provide a functional benefit to the patient. Unilateral conductive hearing loss is associated with various disabilities including difficulty in sound localization and in hearing and understanding speech. Traditionally, otologists have reported the results of middle ear surgery as the closure of the air - bone gap or the reduction in air conduction thresholds. The closure of the air-bone gap refers to improvement of the air conduction thresholds (involving conductive and sensorineural components) to the level of the bone conduction thresholds (sensorineural component). While these provide a measure of the technical success of the operation, they may not always translate into real life benefit for the patient. Hence standardization of results of treatment should be by a method based on subjective perception which benefits patients in real life. Other methods have been used to evaluate the effectiveness of middle ear surgery including questionnaires that evaluate a patient's subjective benefit from surgery. Using questionnaires to evaluate benefit is complicated by the fact that both surgeons and patients want to believe that the operation has succeeded. The two most common methods found in the otologic literature to evaluate benefit from middle ear surgery are the Belfast 15/30 dB rule of thumb and the Glasgow benefit plot. These methods facilitates the assessment of subjective benefit as well as objective achievement, we have employed these two most common methods to estimate patient benefit from middle ear surgery in our study. AIMS AND OBJECTIVES: 1. To compare two methods of predicting the level of hearing benefit following middle ear surgery, namely Glasgow benefit plot and Belfast 15/30 dB rule of Thumb. 2. To correlate hearing benefit as measured by using the above methods with patients' self assessment of his/her hearing status 3. To analyze the differences in hearing improvement by various ossiculoplasties like incus interposition, tragal/ conchal cartilage and autograft malleus. 4. To compare the success rates with surgery on dry and wet ears. 5. To compare success rates with cavity mastoidectomy cases versus those without cavity. MATERIALS AND METHODS: Sixty patients undergoing middle ear surgery were selected at random with no age or sex bias. Only patients with conductive hearing loss were selected. The minimum age was 11 years and maximum age was 48 years. Those cases requiring myringoplasty were excluded from the study. Any allergic or septic focus was ruled out preoperatively. Cases with bilateral ear disease were also taken up and revision cases were also subjected to surgery on 7 occassions. Both wet and dry ears were taken up. Patients were admitted one day before the surgery. Mastoid shaving and local preparation were done in the ward. All cases were operated under general anaesthesia. The types of surgery included in the study were mastoid exploration, tympanoplasty and ossiculoplasty. Apart from a detailed case history, patients were assessed clinically with the help of otoscopy, tuning fork tests, pure tone audiometry, free field hearing tests, X-ray Mastoids and CT Temporal bone were done where applicable. A detailed questionnaire was used (separately to be filled in by the patient and the close first relative of the patient) pre and post operatively, to assess the level of hearing. Patients were followed post operatively for 3 & 6 months. RESULTS AND OBSERVATIONS: There were 38 males and 22 females. Age range was from 11-48 years. The younger patients were more aware of their hearing loss and consisted of 76.6 % of all the patients. The commonest disease was CSOM - tubotympanic (14 cases) and atticoantral (46 cases). Group 1 : Unilateral hearing impairment, asymmetric threshold 12 patients were included in this group. All had pure tone average above 30 dB in one ear; all had interaural difference of more than 10 dB. Preoperative self assessment of hearing loss by patients : Patients presented with varying degrees of subjective hearing impairment, such as diminished hearing from a distance, in group conversation, on telephone, discharge and diminished hearing. Post operatively: Hearing from operated and non-operated ear was same in 6 patients (3 patients had inter aural difference of 12, 12 & 18 dB but claimed symmetric hearing). Group 2 : Bilateral hearing impairment, asymmetric threshold. 40 patients were included in this group and 37 patients had pure tone averages above 30 dB in both ears. 29 patients had inter aural difference of more than 10dB. Patients claimed significant benefit post operatively. Hearing from operated and non-operated ear was same in 33 patients. The prediction by both methods in this group was 100%. 19 patients fell in category 'c' and claimed significant benefit. Group 3 : Bilateral hearing impairment - symmetric threshold 8 patients were included in this group. Pure tone average was less than 30 dB in six cases and interaural difference within 10 dB in 2 cases and 12,12,15,16,25,28,26 dB in 6 patients. They had significant benefit following surgery and claimed that the operated ear was the better hearing ear. As per audiometry, 2 patients fell in category 'c' and claimed significant benefit. As per subjective benefit all these patients claimed significant benefit. Comparing the same with 15/30 dB rule of thumb as per audiometry, the overall positive predictive value was 80% and as per subjective benefit 84%. Applying Z test for significance of difference between the predictive values by pure Tone Audiometry and subjective benefit in both the methods, the difference is not significant since Z is <1.96 at 95% confidence interval. 10 out of 12 patients (83%) in Group I had no difficulty in localizing sound, as only one ear is actually sufficient to localize sound. According to Browning GG (1993), minor head movement can achieve the necessary variation in speech perception level. In Group 3, 8 patients had bilateral symmetric hearing loss as per pure tone audiometry. Pure tone averages in the 0.5,1,2 kHz were same in both ears. This correlates with observations of G.G.Browning (1993), audiometric tests do not measure all aspects of hearing; hence the ear being operated upon should be as per patient's choice. CONCLUSION: 1. The overall success rate of ossiculoplasty in the present study is 80%. 2. In this study its found that Glasgow benefit plot is more sophisticated, graphical, providing a good visual impression whereas Belfast Rule of thumb is easy and simple to use, but, it suffers from the disadvantages of 'all or none phenomenon' with no place for marginal benefit. 3. Hearing improvement with Incus transposition is better followed by tragal and conchal cartilage ossiculoplasty, Homograft Malleus (in descending order). 4. Hearing improvement is better when minimal ossicular disruption is present. (All present > Incus absent > M-I-> M-I-S-) 5. Hearing improvement is better when cholesteatoma is absent (when compared to cholesteatoma cases). 6. Hearing improvement is better with dry ears. 7. Hearing improvement is better when cavity mastoidectomy was not done (when compared to cavity mastoidectomy cases.) 8. Fresh cases do better than revision cases. 9. Cases without granulations do better than those with granulations

Progressive ataxia with oculo-palatal tremor and optic atrophy

The final publication is available at Springer via doi: 10.​1007/​s00415-013-7136-

TRESK is a key regulator of nocturnal suprachiasmatic nucleus dynamics and light adaptive responses

The suprachiasmatic nucleus (SCN) is a complex structure dependent upon multiple mechanisms to ensure rhythmic electrical activity that varies between day and night, to determine circadian adaptation and behaviours. SCN neurons are exposed to glutamate from multiple sources including from the retino-hypothalamic tract and from astrocytes. However, the mechanism preventing inappropriate post-synaptic glutamatergic effects is unexplored and unknown. Unexpectedly we discovered that TRESK, a calcium regulated two-pore potassium channel, plays a crucial role in this system. We propose that glutamate activates TRESK through NMDA and AMPA mediated calcium influx and calcineurin activation to then oppose further membrane depolarisation and rising intracellular calcium. Hence, in the absence of TRESK, glutamatergic activity is unregulated leading to membrane depolarisation, increased nocturnal SCN firing, inverted basal calcium levels and impaired sensitivity in light induced phase delays. Our data reveals TRESK plays an essential part in SCN regulatory mechanisms and light induced adaptive behaviours

Minimally Invasive In Vivo Real-Time Identification of Human Astrocytoma with Sulforhodamine 101

Abstract and poster under embargo until May 31, 2019

Association of British Neurologists: revised (2015) guidelines for prescribing disease-modifying treatments in multiple sclerosis.

In June 1999, the Association of British Neurologists (ABN) first published guidelines for the use of the licensed multiple sclerosis (MS) disease-modifying treatments (at that time β-interferon and glatiramer acetate). The guidelines were revised in 2001 and have been periodically updated since then. In 2002, following the negative assessment of these treatments by the National Institute for Health and Care Excellence (NICE), the MS risk-sharing scheme started, in which patients eligible according to the 2001 ABN guidelines were provided with treatment funded through the UK National Health Service (NHS), and monitored annually for up to 10 years.1 Recruitment to the risk-sharing scheme cohort is complete. Pending a future final evaluation, the UK Department of Health's instruction to NHS funders remains in place: that patients who fulfil the ABN criteria should continue to receive treatment funded through the NHS. The British neurological community has fully accepted the risk-sharing scheme for prescribing β-interferon and glatiramer acetate. Approximately 70 ‘treating centres’ have recruited >5000 patients between 2002 and 2005, and these have been monitored annually for 10 years; many more patients have received these treatments since 2005. The ABN published revised guidelines in 2007, and then again in 2009, following the licensing of natalizumab and mitoxantrone. This 2015 revised guideline replaces former versions. It includes all newly approved or licensed treatments for MS and represents a consensus concerning their use. These guidelines will require future revision as other treatments receive approval (eg, daclizumab and ocrelizumab): we suggest they are reviewed after an interval of no longer than 12 months. The guideline is not intended to provide a complete description of the possible complications and monitoring of disease-modifying treatments in MS; we refer prescribing neurologists to the relevant summaries of product characteristics.PostprintPeer reviewe

A highly efficient human pluripotent stem cell microglia model displays a neuronal-co-culture-specific expression profile and inflammatory response

Microglia are increasingly implicated in brain pathology, particularly neurodegenerative disease, with many genes implicated in Alzheimer's, Parkinson's, and motor neuron disease expressed in microglia. There is, therefore, a need for authentic, efficient in vitro models to study human microglial pathological mechanisms. Microglia originate from the yolk sac as MYB-independent macrophages, migrating into the developing brain to complete differentiation. Here, we recapitulate microglial ontogeny by highly efficient differentiation of embryonic MYB-independent iPSC-derived macrophages then co-culture them with iPSC-derived cortical neurons. Co-cultures retain neuronal maturity and functionality for many weeks. Co-culture microglia express key microglia-specific markers and neurodegenerative disease-relevant genes, develop highly dynamic ramifications, and are phagocytic. Upon activation they become more ameboid, releasing multiple microglia-relevant cytokines. Importantly, co-culture microglia downregulate pathogen-response pathways, upregulate homeostatic function pathways, and promote a more anti-inflammatory and pro-remodeling cytokine response than corresponding monocultures, demonstrating that co-cultures are preferable for modeling authentic microglial physiology

A novel human iPSC model of COL4A1/A2 small vessel disease unveils a key pathogenic role of matrix metalloproteinases

Cerebral small vessel disease (SVD) affects the small vessels in the brain and is a leading cause of stroke and dementia. Emerging evidence supports a role of the extracellular matrix (ECM), at the interface between blood and brain, in the progression of SVD pathology, but this remains poorly characterized. To address ECM role in SVD, we developed a co-culture model of mural and endothelial cells using human induced pluripotent stem cells from patients with COL4A1/A2 SVD-related mutations. This model revealed that these mutations induce apoptosis, migration defects, ECM remodeling, and transcriptome changes in mural cells. Importantly, these mural cell defects exert a detrimental effect on endothelial cell tight junctions through paracrine actions. COL4A1/A2 models also express high levels of matrix metalloproteinases (MMPs), and inhibiting MMP activity partially rescues the ECM abnormalities and mural cell phenotypic changes. These data provide a basis for targeting MMP as a therapeutic opportunity in SVD.</p

TASK-3, two-pore potassium channels, contribute to circadian rhythms in the electrical properties of the suprachiasmatic nucleus and play a role in driving stable behavioural photic entrainment

Stable and entrainable physiological circadian rhythms are crucial for overall health and well-being. The suprachiasmatic nucleus (SCN), the primary circadian pacemaker in mammals, consists of diverse neuron types that collectively generate a circadian profile of electrical activity. However, the mechanisms underlying the regulation of endogenous neuronal excitability in the SCN remain unclear. Two-pore domain potassium channels (K2P), including TASK-3, are known to play a significant role in maintaining SCN diurnal homeostasis by inhibiting neuronal activity at night. In this study, we investigated the role of TASK-3 in SCN circadian neuronal regulation and behavioural photoentrainment using a TASK-3 global knockout mouse model. Our findings demonstrate the importance of TASK-3 in maintaining SCN hyperpolarization during the night and establishing SCN sensitivity to glutamate. Specifically, we observed that TASK-3 knockout mice lacked diurnal variation in resting membrane potential and exhibited altered glutamate sensitivity both in vivo and in vitro. Interestingly, despite these changes, the mice lacking TASK-3 were still able to maintain relatively normal circadian behaviour