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Auditory Neuropathy Spectrum Disorder and Retrocochlear Disorders in Adults and Children
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Distinguishing whether a neuropathy is principally demyelinating or axonal in type is primarily determined histologically following biopsy, clearly not a procedure applicable to the auditory nerve. In the circumstances, electrodiagnostic studies (nerve conduction studies) can provide a functional categorization for the type of neuropathy. A patient with late-onset HSMN, beginning at age 40, and presenting with a hearing loss 10 years later, came to autopsy at the age of 77 years. Histopathological examination of both auditory and sural nerves showed a significant loss of nerve fibres more extensive in the sural nerve than in the auditory nerve. Photomicrographs of a section of the patient’s auditory nerve and an age-matched control showed an extensive loss of large nerve fibres in the former. This woman’s neuropathy was inherited in an autosomal dominant fashion, with genetic analysis of the affected members of the pedigree showing a duplication disorder on the MPZ gene of chromosome 1. The MPZ gene (myelin protein zero) was the first gene associated with auditory neuropathy in patients with Charcot–Marie–Tooth disease (CMT). The MPZ gene codes for a protein required for myelin formation and adhesion. Preserved cochlear hair cells were found on postmortem examination of a patient with CMT together with decreased spiral ganglion cells and degeneration of the residual axons. The proximal auditory nerve showed axonal loss and incomplete myelination at the entrance to the brainstem. [Level 1 evidence]
Peripheral Neuropathies
Published in John W. Scadding, Nicholas A. Losseff, Clinical Neurology, 2011
Gareth Llewelyn, Robert Powell
A more severe demyelinating form, Dejerine–Sottas disease (previously known as CMT3, but now recognized as a severe variant of CMT1) is characterized by early childhood onset, and can be due to point mutations in PMP22 and MPZ.
Myelin-associated proteins are potential diagnostic markers in patients with primary brain tumour
Published in Annals of Medicine, 2021
Olga M. Koper-Lenkiewicz, Anna J. Milewska, Joanna Kamińska, Karol Sawicki, Robert Chrzanowski, Justyna Zińczuk, Joanna Reszeć, Marzena Tylicka, Ewa Matuszczak, Joanna Matowicka-Karna, Zenon Mariak, Mariusz W. Mucha, Robert Pawlak, Violetta Dymicka-Piekarska
One limitation of the study could be the sensitivity of the applied ELISA tests for Nogo-A, MAG, and OMgp concentration evaluation. The standard curve points of MAG and OMgp ELISA kits were expressed in ng/mL. On the contrary, for Nogo-A the standard curve points were expressed in pg/mL. These differences in the sensitivity of the ELISA kits may explain why some MAG and OMgp results were below the detection range. Another study limitation could be the specificity of the applied ELISA kits. Thus, we asked the ELISA kit suppliers for the anti-Nogo-A, anti-MAG, and anti-OMgp antibodies specificity. In the case of the Nogo-A test, the ELISA vendor used UniProtKB: Q9NQC (1-200aa) antibody, which is only human-specific. In the case of the MAG and OMgp tests, we have obtained information that the used kits did not reveal any cross-reactivity with myelin basic protein (MBP), myelin protein zero, and myelin protein two. The possible cross-reactivity of the OMgp ELISA kit with GPIbαβ was not tested.
Targeting mitochondria in dermatological therapy: beyond oxidative damage and skin aging
Published in Expert Opinion on Therapeutic Targets, 2022
Tongyu C Wikramanayake, Jérémy Chéret, Alec Sevilla, Mark Birch-Machin, Ralf Paus
In the context of how best to target mitochondrial function in human skin, we are particularly intrigued by a mysterious, mitochondrially localized protein, called Myelin Protein Zero-like 3 (MPZL3) [353,354]. MPZL3 has recently emerged as a key regulator of various aspects of skin differentiation [353], including epidermal morphogenesis and barrier function [241,353,355,356], sebaceous gland differentiation [355,357,420] and hair follicle cycling [353,358] (Figure 3). Curiously, MPZL3 is currently not listed in MitoCarta3.0 [359] (broadinstitute.org), possibly explaining why MPZL3 has largely been ignored by mainstream mitochondrial research.
Thr124Met myelin protein zero mutation mimicking motor neuron disease
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2022
Giulia Bisogni, Angela Romano, Amelia Conte, Giorgio Tasca, Daniela Bernardo, Marco Luigetti, Andrea Di Paolantonio, Gian Maria Fabrizi, Agata Katia Patanella, Emiliana Meleo, Mario Sabatelli
The mechanism by which alteration of MPZ cause axonal degeneration in the absence of demyelination is still unclear. MPZ is a transmembrane protein exclusively expressed in Schwann cells with an immunoglobulin-like domain and acts as an adhesion protein playing a major structural role in myelin compaction. Schwann cells, among other functions, provide trophic support to the axon, thus explaining the variable degree of axonal loss that generally associates with all forms of primary demyelinating neuropathies (11, 12).