Severe Charcot‐Marie‐Tooth disease type 1E caused by a novel p.Phe84Leufs*24 PMP22 point mutation

We report a severe phenotype of Charcot‐Marie‐Tooth (CMT) disease type 1E caused by a novel p.Phe84Leufs*24 PMP22 point mutation. Ultrastructural examination of a nerve biopsy showed non‐ or partly myelinated axons which were surrounded by “onion bulb” formations mainly composed of concentric basement membranes and characterized by the presence of prominent concentric or longitudinal collagen fibrils interspersed with basement membranes. PMP22 point mutations are rare and responsible for polyneuropathies often demyelinating with onion bulb formations composed of concentric and redundant basement membranes. Entrapment of prominent collagen fibrils within onion bulb formations is unusual, even in the large spectrum of CMT disease with long duration and severe damage.     

Mutational analysis of Greek patients with suspected hereditary neuropathy with liability to pressure palsies (HNPP): a 15‐year experience

There has been limited information from population studies regarding the overall frequency of the common 1.5‐Mb 17p11.2 deletion and even scarcer data regarding the overall frequency of PMP22 micromutations in patients with a clinical suspicion of hereditary neuropathy with liability to pressure palsies (HNPP). We have analysed 100 consecutive Greek patients referred for HNPP genetic testing over a 15‐year period to our Neurogenetics Unit in Athens, a reference centre for all regions of Greece. All patients were screened for the 1.5‐Mb deletion and a selected subgroup of deletion‐negative patients for PMP22 micromutations. Mutation‐positive and mutation‐negative patients were compared for various clinical parameters. In total, 54 mutation‐positive patients were identified. In index cases, the deletion frequency was 47.8%, and the PMP22 micromutation frequency was 2.2%. Within mutation‐positive patients, the common deletion represented 95.7% and PMP22 micromutations 4.3% of cases. Two previously reported PMP22 micromutations (c.364_365delCC and c.79‐2A>G) were detected. HNPP index cases had a 2.8–1 male‐to‐female ratio, similar to mutation‐negative patients. A typical phenotype (recurrent or isolated palsies) was present in 82.4% of symptomatic HNPP cases, significantly higher than mutation‐negative patients. Sensitivity of proposed electrophysiological diagnostic criteria for HNPP was calculated at 95.7% and specificity at 80.5%. In conclusion, the common HNPP deletion accounts for ～50% and PMP22 micromutations for ～2% of cases in a large consecutive cohort of patients with suspected HNPP. The mutational and phenotypic spectrum of HNPP is similar in the Greek population compared with other populations. Proposed electrophysiological diagnostic criteria perform satisfactorily in everyday clinical practice.     

Coexistence of a T118M PMP22 missense mutation and chromosome 17 (17p11.2‐p12) deletion

Introduction: We describe a 6‐year‐old girl with a T118M PMP22 mutation and heterozygous deletion of PMP22 on chromosome 17 (17p11.2‐p12) resulting in a severe sensorimotor polyneuropathy. Methods: This study is a case report in which the relevant mutations are described. Results: Foot pain, cavovarus feet, tibialis anterior atrophy, absent reflexes, and inability to walk were found when the patient was age 6 years. Nerve conduction studies showed evidence of a sensorimotor polyneuropathy and compressive mononeuropathies of bilateral median nerves at the wrist and ulnar nerves at the elbow. Genetic testing revealed deletion of a PMP22 allele and T118M PMP22 mutation in the remaining allele. Conclusions: The severe sensorimotor polyneuropathy and hereditary neuropathy with liability to pressure palsies (HNPP) in this patient was likely a consequence of both decreased expression of PMP22 causing features consistent with HNPP and unopposed expression of the T118M mutant form of PMP22 that is relatively benign in the heterozygous state. The T118M mutant form of PMP22 can be disease‐modifying in the appropriate circumstances. Muscle Nerve 52 : 905–908, 2015     

Genetic factors for nerve susceptibility to injuries – lessons from PMP22 deficiency

Genetic factors may be learnt from families with gene mutations that render nerve-injury sus- ceptibility even to ordinary physical activities. A typical example is hereditary neuropathy with liability to pressure palsies （HNPP）. HNPP is caused by a heterozygous deletion of PMP22 gene. PMP22 deficiency disrupts myelin junctions （such as tight junction and adherens junctions）, leading to abnormally increased myelin permeability that explains the nerve susceptibility to injury. This finding should motivate investigators to identify additional genetic factors contribut- ing to nerve vulnerability of injury.     

Mutational analysis of GJB1, MPZ, PMP22, EGR2, and LITAF/SIMPLE in Serbian Charcot-Marie-Tooth patients

We report the results of mutational analysis in the following genes: GJB1 , MPZ , PMP22 , EGR2 , and LITAF/SIMPLE in 57 Charcot-Marie-Tooth (CMT) patients of Serbian origin without the PMP22 duplication. We found 10 different mutations in 14 CMT patients: 6 mutations in GJB1 , 3 in MPZ , and 1 in PMP22 . Five of six GJB1 mutations are reported for the first time, and the most frequent one appears to be a founder mutation in the Serbian population. No mutations were found in EGR2 or LITAF . Thus, GJB1 mutation analysis should be done in patients without the PMP22 duplication and male-to-male transmission of CMT.     

Developmental immunohistochemistry of the 22 kDa peroxisomal membrane protein in the human brain

We studied immunohistochemically the 22 kDa peroxisomal membrane protein (PMP 22). In the control brain, the immunopositive neurons for PMP 22 appeared 2–3 weeks earlier than those for peroxisomal enzymes. PMP 22-immunopositive glial cells appeared at 26–27 gestational weeks, increased with gestational age, and were rarely recognized after 1 year of age. In the patients with Zellweger syndrome, PMP 22-immunoreactivity was recognized in neurons, glias, liver and kidney cells.     

A prospective,split-face,double-blinded,randomized study of the efficacy and safety of a fractional 1064-nm Q-switched Nd:YAG laser for photoaging-associated mottled pigmentation in Asian skin

Background: Laser toning using low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum laser (QSNY) has gained popularity in the treatment of photoaging-associated mottled pigmentation (PMP). However, hypopigmentation or lack of efficacy has been reported depending on the fluences used. Objective: To compare a novel fractional 1064-nm QSNY with conventional 1064-nm QSNY for the treatment of photoaging-associated mottled pigmentary lesions except epidermal lesions of lentigines and freckles through a randomized, split-face, double-blind study. Materials and methods: Thirteen Asian women were treated every week for 6 weeks with fractional 1064-nm QSNY on one side of the face and conventional 1064-nm QSNY on the other side. We evaluated the pigmentation area and severity index (PSI), melanin index, erythema index, and the patient's global assessment of improvement. Results: At three months post-treatment, the PSI score improved compared with baseline, by 14.48% on the conventional 1064-nm QSNY side and 21.81% on the fractional 1064-nm QSNY side. Both groups showed improvements in the melanin index. Conclusion: Both fractional 1064-nm QSNY and strictly low-fluence conventional 1064-nm QSNY are moderately effective against PMP and other photoaging signs. Fractional laser toning shows better subjective outcomes than conventional toning.     

Determination of genomic copy number with quantitative microsphere hybridization

We developed a novel quantitative microsphere suspension hybridization (QMH) assay for determination of genomic copy number by flow cytometry. Single copy (sc) products ranging in length from 62 to 2,304 nucleotides [Rogan et al., 2001; Knoll and Rogan, 2004] from ABL1 (chromosome 9q34), TEKT3 (17p12), PMP22 (17p12), and HOXB1 (17q21) were conjugated to spectrally distinct polystyrene microspheres. These conjugated probes were used in multiplex hybridization to detect homologous target sequences in biotinylated genomic DNA extracted from fixed cell pellets obtained for cytogenetic studies. Hybridized targets were bound to phycoerythrin-labeled streptavidin; then the spectral emissions of both target and conjugated microsphere were codetected by flow cytometry. Prior amplification of locus-specific target DNA was not required because sc probes provide adequate specificity and sensitivity for accurate copy number determination. Copy number differences were distinguishable by comparing the mean fluorescence intensities (MFI) of test probes with a biallelic reference probe in genomic DNA of patient samples and abnormal cell lines. Concerted 5' ABL1 deletions in patient samples with a chromosome 9;22 translocation and chronic myelogenous leukemia were confirmed by comparison of the mean fluorescence intensities of ABL1 test probes with a HOXB1 reference probe. The relative intensities of the ABL1 probes were reduced to 0.59+/-0.02 fold in three different deletion patients and increased 1.42+/-0.01 fold in three trisomic 9 cell lines. TEKT3 and PMP22 probes detected proportionate copy number increases in five patients with Charcot-Marie-Tooth Type 1a disease and chromosome 17p12 duplications. Thus, the assay is capable of distinguishing one allele and three alleles from a biallelic reference sequence, regardless of chromosomal context.     

Axonal damage and demyelination in long-term dorsal root ganglia cultures from a rat model of Charcot-Marie-Tooth type 1A disease

Clinical progression in hereditary and acquired demyelinating disorders of both the central and peripheral nervous system is mainly due to a time-dependent axonal impairment. We established 90-day dorsal root ganglia (DRG) cultures from a rat model of Charcot-Marie-Tooth type 1A (CMT1A) neuropathy to evaluate the structure of myelin and axons, and the expression of myelin-related proteins and cytoskeletal components, by morphological and molecular techniques. Both wild-type and CMT1A cultures were rich in myelinated fibres. Affected cultures showed dysmyelinated internodes and focal myelin swellings. Furthermore, uncompacted myelin and smaller axons with increased neurofilament (NF) density were found by electron microscopy, and Western blots showed higher levels of nonphosphorylated NF. Confocal microscopy demonstrated an abnormal distribution of the myelin-associated glycoprotein which, instead of being expressed at the noncompact myelin level, showed focal accumulation along the internodes while other myelin proteins were normally distributed. These findings suggest that CMT1A DRG cultures, similarly to the animal model and human disease, undergo axonal atrophy over a period of time. This model may be utilized to study the molecular changes underlying demyelination and secondary axonal impairment. As axonal damage may occur after just 3 months and tissue cultures represent a strictly controlled environment, this model may be ideal for testing neuroprotective therapies.     

Nerve ultrasound findings differentiate Charcot-Marie-Tooth disease (CMT) 1A from other demyelinating CMTs

Objective

Ulnar/median motor nerve conduction velocity (MNCV) is ≤38?m/s in demyelinating Charcot-Marie-Tooth disease (CMT). Previous nerve high resolution ultrasound (HRUS) studies explored demyelinating CMT assuming it as a homogeneous genetic/pathological entity or focused on CMT1A.