Charcot-marie-tooth disease: seventeen causative genes

Yeast models for Charcot-Marie-Tooth disease-causing aminoacyl-tRNA synthetase alleles reveal the cellular basis of disease

Charcot-Marie-Tooth disease (CMT) is a genetically diverse hereditary disorder that affects the motor and sensory nerves, impacting about 1 in 2500 people. It can be inherited through autosomal dominant (AD), autosomal recessive (AR), or X-linked genetic patterns. CMT2, one of the primary subtypes, is characterized by axonal degeneration and commonly presents with muscle weakness, atrophy, foot deformities, and sensory loss. Aminoacyl-tRNA synthetases (aaRSs) play an important role in the genetic underpinnings of CMT2, with more than 60 disease-causing alleles identified across eight different aaRSs, including alanyl-, asparaginyl-, histidyl-, glycyl-, methionyl-, tryptophanyl-, seryl-, and tyrosyl-tRNA synthetases. Mutations in aaRS genes can lead to destabilization of the enzyme, reduced aminoacylation, and aberrant protein complex formation. Yeast as a simple organism provides a robust model system to study the pathogenic effects of aaRS CMT mutations. In this review, we discuss the advantages and limitations of the yeast model systems for CMT2-causative mutations in aaRS.

Neuromuscular monitoring of a patient with Charcot-Marie-Tooth disease; which monitoring technique is adequate? - A case report and literature review

BACKGROUND

Charcot-Marie-Tooth disease (CMTD) is a hereditary polyneuropathy associated with a life-threatening risk of pulmonary complications.

CASE

A 61-year-old male with CMTD for 40 years was admitted for the drainage of an abscess in his left ankle. Total intravenous anesthesia was administered, and an electromyography device was attached to the hand for neuromuscular monitoring; however, the response was not measured. Kinemyography and acceleromyography devices were attached to both hands, and responses were obtained. After neuromuscular blockade (NMB) with rocuronium 0.6 mg/kg, the train-of-four (TOF) response on kinemyography was normally measured, but the post-tetanic count on acceleromyography consistently showed 0 during anesthesia. Sugammadex 200 mg was injected to reverse the NMB. After 5 min, the TOF ratios for kinemyography and acceleromyography exceeded 90%. The patient recovered without any complications.

CONCLUSIONS

For CMTD patients, acceleromyography or kinemyography is superior to electromyography, and sugammadex can be used to reverse NMB successfully.

Treating PMP22 gene duplication-related Charcot-Marie-Tooth disease: the past, the present and the future

Charcot-Marie-Tooth (CMT) disease is the most frequent inherited neuropathy, affecting 1/1500 to 1/10000. CMT1A represents 60%-70% of all CMT and is caused by a duplication on chromosome 17p11.2 leading to an overexpression of the Peripheral Myelin Protein 22 (PMP22). PMP22 gene is under tight regulation and small changes in its expression influences myelination and affect motor and sensory functions. To date, CMT1A treatment is symptomatic and classic pharmacological options have been disappointing. Here, we review the past, present, and future treatment options for CMT1A, with a special emphasis on the highly promising potential of PMP22-targeted small interfering RNA and antisense oligonucleotides.

Exome Sequencing Reveals a Novel PRPS1 Mutation in a Family with CMTX5 without Optic Atrophy

Background

X-linked Charcot-Marie-Tooth disease type 5 (CMTX5) is caused by mutations in the gene encoding phosphoribosyl pyrophosphate synthetase I (PRPS1). There has been only one case report of CMTX5 patients. The aim of this study was to identify the causative gene in a family with CMTX with peripheral neuropathy and deafness.

Case Report

A Korean family with X-linked recessive CMT was enrolled. The age at the onset of hearing loss of the male proband was 5 months, and that of steppage gait was 6 years; he underwent cochlear surgery at the age of 12 years. In contrast to what was reported for the first patients with CMTX5, this patient did not exhibit optic atrophy. Furthermore, there was no cognitive impairment, respiratory dysfunction, or visual disturbance. Assessment of his family history revealed two male relatives with very similar clinical manifestations. Electrophysiological evaluations disclosed sensorineural hearing loss and peripheral neuropathy. Whole-exome sequencing identified a novel p.Ala121Gly (c.362C>G) PRPS1 mutation as the underlying genetic cause of the clinical phenotype.

Conclusions

A novel mutation of PRPS1 was identified in a CMTX5 family in which the proband had a phenotype of peripheral neuropathy with early-onset hearing loss, but no optic atrophy. The findings of this study will expand the clinical spectrum of X-linked recessive CMT and will be useful for the molecular diagnosis of clinically heterogeneous peripheral neuropathies.