Khabibrakhmanov Aidar Nazimovich

Dystonia due to the KMT2B mutation (DYT-KMT2B) is a relatively common cause of progressive generalized dystonia in children; it can potentially account for up to 10—20% of cases of generalized dystonia with early onset. However, only one case of DYT-KMT2B has been reported In Russia to date. Determining the genetic variant and assessing clinical manifestations can help identify this dystonia and determine the indications for drug treatment, including botulinum therapy and neurosurgical intervention. We present a clinical case of a girl with a DYT-KMT2B onset at the age of 6 years and a review of the literature.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the death of upper and lower motor neurons. Numerous studies show that structural and functional impairments of neuromuscular junctions (NMJ) occur as early as the presymptomatic stage of ALS. NMJ involvement is independent and one of the primary events in ALS pathogenesis. Aim: to review the data on characteristics and mechanisms of NMJ dysfunction at pre- and postsynaptic levels in ALS patients and a transgenic animal model of the disease. Furthermore, we report on the dysfunction of perisynaptic Schwann cells and impaired mechanisms of motor neuron and skeletal muscle interaction in ALS, with a focus on reviewed publications on targeting of molecular mechanisms underlying NMJ dysfunction and disruption in ALS. The NMJ may be a potential target for novel therapeutic approaches for ALS.

Objective. Assessment of plasma and salivary acetylcholinesterase (AChE) activity in patients with amyotrophic lateral sclerosis (ALS) and in an animal model of the disease. Material and methods. We studied 41 participants, aged 31 to 71 years, including 17 patients with diagnosed ALS (ALS group, average age 62.3±2.2), 9 patients with ALS mimics (disease control, average age 58.1±2.9), and 15 healthy people (normal control, average age 57.7±2.3). Plasma and salivary AChE activity was measured by using the Ellman colorimetric method. ALS severity was assessed using the ALSFRS-R scale. The King’s College staging system and the Milano-Torino Scale (MiToS) were used to determine the stage of the disease. Transgenic FUS-mice were used as ALS model. Results. Plasma AChE activity in the ALS group did not significantly differ from the control groups. There was also no significant correlation between plasma AChE activity and disease parameters such as the stage, duration, rate of progression, and severity. In transgenic FUS-mice plasma AChE activity also did not differ from wild-type mice. However, it has been shown that patients with ALS have significantly higher saliva AChE activity compared to normal controls. However, patients with the bulbar form of ALS had significantly higher values of salivary AChE activity compared to healthy controls. Conclusion. In patients with the bulbar form of ALS, an increase in salivary AChE activity was noted, which can be used for diagnostic and prognostic purposes. There is no significant change in plasma AChE activity in ALS patients.

TRPV1 represents a non-selective transient receptor potential cation channel found not only in sensory neurons, but also in motor nerve endings and in skeletal muscle fibers. However, the role of TRPV1 in the functioning of the neuromuscular junction has not yet been fully established. In this study, the Levator Auris Longus muscle preparations were used to assess the effect of pharmacological activation of TRPV1 channels on neuromuscular transmission. The presence of TRPV1 channels in the nerve terminal and in the muscle fiber was confirmed by immunohistochemistry. It was verified by electrophysiology that the TRPV1 channel agonist capsaicin inhibits the acetylcholine release, and this effect was completely absent after preliminary application of the TRPV1 channel blocker SB 366791. Nerve stimulation revealed an increase of amplitude of isometric tetanic contractions upon application of capsaicin which was also eliminated after preliminary application of SB 366791. Similar data were obtained during direct muscle stimulation. Thus, pharmacological activation of TRPV1 channels affects the functioning of both the pre- and postsynaptic compartment of the neuromuscular junction. A moderate decrease in the amount of acetylcholine released from the motor nerve allows to maintain a reserve pool of the mediator to ensure a longer signal transmission process, and an increase in the force of muscle contraction, in its turn, also implies more effective physiological muscle activity in response to prolonged stimulation. This assumption is supported by the fact that when muscle was indirect stimulated with a fatigue protocol, muscle fatigue was attenuated in the presence of capsaicin. Graphical Abstract

Amyotrophic lateral sclerosis (ALS) is manifested as skeletal muscle denervation, loss of motor neurons and finally severe respiratory failure. Mutations of RNA-binding protein FUS are one of the common genetic reasons of ALS accompanied by a ‘dying back’ type of degeneration. Using fluorescent approaches and microelectrode recordings, the early structural and functional alterations in diaphragm neuromuscular junctions (NMJs) were studied in mutant FUS mice at the pre-onset stage. Lipid peroxidation and decreased staining with a lipid raft marker were found in the mutant mice. Despite the preservation of the end-plate structure, immunolabeling revealed an increase in levels of presynaptic proteins, SNAP-25 and synapsin 1. The latter can restrain Ca²⁺-dependent synaptic vesicle mobilization. Indeed, neurotransmitter release upon intense nerve stimulation and its recovery after tetanus and compensatory synaptic vesicle endocytosis were markedly depressed in FUS mice. There was a trend to attenuation of axonal [Ca²⁺]_in increase upon nerve stimulation at 20 Hz. However, no changes in neurotransmitter release and the intraterminal Ca²⁺ transient in response to low frequency stimulation or in quantal content and the synchrony of neurotransmitter release at low levels of external Ca²⁺ were detected. At a later stage, shrinking and fragmentation of end plates together with a decrease in presynaptic protein expression and disturbance of the neurotransmitter release timing occurred. Overall, suppression of synaptic vesicle exo–endocytosis upon intense activity probably due to alterations in membrane properties, synapsin 1 levels and Ca²⁺ kinetics could be an early sign of nascent NMJ pathology, which leads to neuromuscular contact disorganization.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that has no effective treatment. To date, ALS is considered as a multifactorial heterogeneous disease, in which the death of motor neurons is a final result of the different pathological pathways. Modern diagnostic criteria and classification of ALS do not take into account all heterogeneity of the disease. Despite the development of molecular neurobiology and neurophysiology, genetics, and technology, significant progress in understanding the pathogenesis of ALS, the disease is diagnosed primarily on the basis of clinical manifestations. In recent years, a number of clinical trials of promising drugs have failed to show positive results. Among the reasons for these failures are variability of ALS forms, patients enrollment already at a late stage of the disease, the lack of use of biomarkers for patients selection and drugs' pharmacodynamics assessment. The study of biomarkers and their implementation in clinical practice can help to solve these problems. Here we will discuss the fluid-based biomarkers for ALS.

A comprehensive work‐up, clinical correlation, and differential diagnosis are needed to determine if abnormal findings such us hydromyelia in ALS patients are causative or incidental in order to rule out other, more curable conditions that resemble ALS.