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At least 1,387 records · Page 77Linked to original sources
PubMed2005

Phenotypes of the N88S Berardinelli-Seip congenital lipodystrophy 2 mutation.

Recently, two missense mutations (N88S, S90L) in the Berardinelli-Seip congenital lipodystrophy gene have been identified in autosomal dominant distal hereditary motor neuropathy and Silver syndrome. We report the phenotypic consequences of the N88S mutation in 90 patients of 1 large Austrian family and two unrelated German families. Variation in the clinical and electrophysiological phenotype enabled us to distinguish six subtypes. In 4.4%, the disorder was not penetrant. Twenty percent of the patients were subclinically affected; some of these patients could only be detected by pathological nerve conduction studies. A distal hereditary motor neuropathy type V phenotype characterized by predominant hand muscle involvement was found in 31.1%, whereas 14.5% showed typical Silver syndrome with amyotrophy of the small hand muscles and spasticity of the lower extremities. Moreover, the phenotype present in 20% was compatible with Charcot-Marie-Tooth disease. In 10%, the clinical diagnosis of pure or complicated hereditary spastic paraparesis was made. Electrophysiological studies showed an axonal neuropathy but also chronodispersion of compound motor action potentials and conduction blocks. Sensory nerve conduction studies were rarely pathological. Our study indicates that the dominant N88S mutation in the Berardinelli-Seip congenital lipodystrophy gene 2 leads to a broad spectrum of motor neuron disorders.

Action Potentials↗
PubMed2005

Severe neuropathy with leaky connexin32 hemichannels.

X-linked Charcot-Marie-Tooth disease is one of a set of diseases caused by mutations in gap junction proteins called connexins. We identified a connexin32 missense mutation (F235C) in a girl with unusually severe neuropathy. The localization and trafficking of the mutant protein in cell culture was normal, but electrophysiological studies showed that the mutation caused abnormal hemichannel opening, with excessive permeability of the plasma membrane and decreased cell survival. Abnormal leakiness of connexin hemichannels is likely a mechanism of cellular toxicity in this and perhaps other diseases caused by connexin mutations.

Adolescent↗
PubMed1979

Hyperexcitability of motor and sensory neurons in neuromyotonia.

Two members of a family with a neuropathy resembling Charcot-Marie-Tooth disease were unable to relax their muscles after voluntary contraction. Muscle spasm often outlasted voluntary contraction by 30 seconds or more before subsiding into myokymia and fasciculations. The posture of the hand during muscle spasm resembled that of tetany, and Trousseau's and Chvostek's signs were present although no abnormality of calcium or magnesium metabolism could be demonstrated. Muscle spasms ceased during medication with carbamazepine, 600 mg daily. Nerve stimulation, electromyography, and regional neuromuscular blockade with curare indicated that the condition originated in peripheral nerve, while microneurographic recordings showed that sensory as well as motor fibers were hyperexcitable. Sural nerve biopsy revealed axonal degeneration involving myelinated and unmyelinated fibers. It was concluded that the neural hyperexcitability is caused by a membrane defect resulting in a low threshold for excitation throughout the length of the axon.

Adult↗
PubMed1994

Prevalence of the 1.5-Mb 17p deletion in families with hereditary neuropathy with liability to pressure palsies.

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder of the peripheral nerves leading to increased susceptibility to mechanical traction or compression. Some patients have been shown to be carriers of a 1.5-Mb deletion in chromosome 17p11.2, which corresponds to the duplicated region present in most patients with Charcot-Marie-Tooth disease type 1A. Recently, evidence has been presented that the deletion is not the only cause of HNPP. To determine the prevalence of the 1.5-Mb deletion, we have examined 22 unrelated families with HNPP in the following two ways: by polymerase chain reaction analysis of marker loci D17S122 and D17S261, and by gene dosage measurements with DNA probes for D17S122 (VAW409R3a) and D17S125 (VAW412R3a) and for the PMP-22 gene. The efficiency and sensitivity of these methods is discussed. Our results show that the prevalence of the 17p deletion in our families with HNPP is 68%. One patient, presenting as a sporadic case, was found to be affected by a de novo deletion in the paternal chromosome. Single-strand conformation analysis of the protein-coding region of the PMP-22 gene did not reveal any mutation in patients from the 7 families lacking the 17p deletion. As a group, these families could not be distinguished by clinical, electrophysiological, or morphological features from the families with the deletion.

Chromosomes, Human, Pair 17↗
PubMed1993

The molecular genetics of myelination: an update.

Recent molecular genetic studies have provided new insights into the structure and function of 2 of the major integral membrane proteins of myelin--the proteolipid protein (PLP) and protein zero (P0)--and have uncovered a third such protein--PMP22/gas3. The rumpshaker mouse has been shown to carry a point mutation in the PLP gene that uncouples a deleterious effect on CNS myelin assembly, which these mice exhibit, from oligodendrocyte degeneration and cell death, which they do not. The developmental importance of the P0 protein in PNS myelination has been dramatically demonstrated by the analysis of loss-of-function mutations engineered through the expression of antisense RNA and through the insertional inactivation of the P0 gene by homologous recombination in embryonic stem cells and the generation of P0-deficient mice. The cloned promoter of the P0 gene has been shown to drive quantitative, Schwann cell-specific expression of heterologous genes in transgenic mice. The PMP22/gas3 gene, previously cloned from fibroblast cell lines, has been found to encode an axonally regulated Schwann cell protein that is assembled into PNS myelin. Importantly, this gene appears to be the target of mutations that result in the Trembler alleles in mice, and in Charcot-Marie-Tooth disease Type 1a, the most common inherited peripheral neuropathy in humans.

Animals↗
PubMed1997

Eruption times of third molars in young rural Nigerians.

The eruption pattern of third molar amongst 1071 rural Nigerians (523 males and 548 females) aged 11-21 years was assessed. The earliest age at which the third molar erupted for males and females was 14 and 13 years respectively with females significantly ahead of males (P < 0.01). A full compliment of erupted third molars was recorded at age 14 years in 1.1 per cent of the population. However, the mean age for the eruption of 1, 2, or 3 and all third molars were 16.58 and 17.50 years respectively. Whilst third molar-eruption was significantly earlier in the mandible, no right-left side differences were found. Problems often associated with the erupting third molars are likely to be seen earlier in young rural Nigerians than in the western countries.

Adolescent↗
PubMed1997

Planning future general anaesthetic services in paediatric dentistry on the basis of evidence: an analysis of children treated in the Day Stay Centre at the Royal Hospitals NHS Trust, London, between 1985-95.

This study aimed to provide evidence for future planning of general anaesthetic services in Paediatric Dentistry. An audit was carried out on children (< or = 17 years) with special needs who were treated under general anaesthesia in the Day Stay Centre at The Royal Hospitals NHS Trust, London, between 1985-95. During these years, 586 child patients were treated, of which 350 had medical complications and/or mental disabilities. Although the number of peri-operative admissions were low (11 planned and 9 emergency), it highlighted the necessity for these patients to be treated in a hospital. Comprehensive dental treatments were carried out which included 1630 deciduous and 596 permanent tooth restorations, and 1382 deciduous and 261 permanent tooth extractions. These patients had follow-up preventive support in the Dental Institute and the readmission rate for further dental treatment under general anaesthesia was low (14 per cent). Comparing the results between 1985-87, 1988-91 and 1992-95 periods, there was a trend for more patients, travelling longer distances, to be treated in the latter periods. It is suggested that more centres with appropriate equipment and trained staff need to be established to meet the increased demand.

Adolescent↗
PubMed1999

The aetiology of the non-carious cervical lesion.

Erosion and abrasion have been widely reported as causes of non-carious cervical lesions (NCCL). However, more recently, tooth flexure has been implicated in the formation of these lesions generating renewed interest in the pathogenesis of the non-carious loss of cervical tooth substance. This paper considers the causes of erosion and abrasion, related to modern lifestyles, and reviews the literature concerning tooth flexure as a cause of NCCL. A description of different types of NCCL is given, as an aid to determining the aetiology, yet at the same time accepting that the causation and pathogenesis of NCCL is probably multi-factorial resulting in many different clinical presentations. Consideration is given to the indications for treatment of NCCL and to the selection of materials for restoring such defects.

Dental Materials↗
PubMed2001

Identification of a positive regulatory element in the myelin-specific promoter of the PMP22 gene.

Over- and under expression of the 22 kDa peripheral myelin protein (PMP22) results in dysmyelinating peripheral neuropathies, such as Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy, with the liability to pressure palsies (HNPP). Expression of the PMP22 gene is driven by two alternative promoters, P1 and P2, with transcripts originating from P1 associated with peripheral nerve myelination by Schwann cells. Transient transfections of constructs containing P1 (3.5 kb) or P2 (2.5 kb) resulted in high levels of reporter gene expression in the RT4-D6P2T schwannoma cell line. Serial deletions of P1 revealed that region P1-A (-105 to -43), situated upstream of the minimal promoter, contained a positive regulatory element. The 62 bp P1-A region conferred in cis a sevenfold increase in expression of luciferase driven by a heterologous promoter in an orientation-dependent manner. Interspecies comparison of the P1-A region revealed a 98% degree of identity between the human, mouse, and rat sequences. A prominent sequence-dependent DNA-protein complex (C-I) was detected in electrophoretic mobility shift assays with P1-A using RT4-D6P2T nuclear extract and was localized to a minimal 21 bp region within P1-A. Site-directed mutagenesis of this region revealed nucleotides at positions -46 to -43 as being necessary for formation of C-I. Functional analysis of the mutated P1-A element indicated that positions -46 and -45 were essential for transactivation mediated by this element. Characterization of the transacting factor(s) interacting with this key regulatory element will shed light on its role in regulating peripheral nerve myelination.

Base Sequence↗
PubMed2005

An 8.5-kb segment of the PMP22 promoter responds to loss of axon signals during Wallerian degeneration, but does not respond to specific axonal signals during nerve regeneration.

Altered expression of the PMP22 gene causes Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP). We have examined the promoter activity of 8.5 kb upstream of the first coding exon of the rat peripheral myelin protein-22 (rPmp22) gene in transgenic mice. We found that the -8.5 kb rPmp22/chloramphenicol acetyl transferase (CAT)/beta-galactosidase (lacZ) construct directs reporter gene expression in a weakly developmental and tissue-specific pattern, consistent with the expression pattern of the endogenous Pmp22 gene. The -8.5 kb rPmp22/CAT/lacZ transgene responds to loss of axonal signals during Wallerian degeneration but unlike the endogenous Pmp22 gene, the transgene fails to respond to axonal signals during nerve regeneration after a sciatic nerve crush injury. In conclusion, the function of the -8.5 kb rPmp22/CAT/lacZ transgene suggests that there are separable regulatory elements in the rPmp22 gene that respond differently to axonal signals received by Schwann cells during nerve development, and during remyelination.

Animals↗
PubMed2006

Myelin protein zero: mutations in the cytoplasmic domain interfere with its cellular trafficking.

The cytoplasmic domain of myelin protein zero (MPZ), the principal protein of peripheral myelin, undergoes phosphorylation on several serine residues and a tyrosine group that is maximal during peak nerve myelination. Mutations that could affect MPZ phosphorylation cause the inherited neuropathy, Charcot-Marie-Tooth disease Type 1B. To investigate a possible role for phosphorylation in regulation of MPZ trafficking within the cell, we expressed wild-type and mutated MPZ-enhanced green fluorescent protein (GFP) fusion proteins in cultured Schwann-like cells. Whereas wild-type protein is present almost entirely at the cell surface, mutation of serine 204 to alanine or at a nearby presumed PKC substrate motif (198RSTK201) causes 40-60% of protein to be retained in the cytoplasm. Mutation of S204 to aspartate, which introduces a permanent negative charge, also impairs MPZ movement to the plasma membrane. In contrast, tyrosine 191 mutation has no effect on MPZ cellular distribution. Simultaneous alteration of S204 and Y191 produces much less perturbation of MPZ trafficking than mutation of S204 alone. Colocalization studies showed that mutated MPZ-EGFP trapped in the cytoplasm associates with all organelles in the secretory pathway. Previous studies have shown that cytoplasmic mutations at serine, but not tyrosine phosphorylation sites, abolish MPZ adhesive properties. Our results suggest that this loss of adhesion may be due, at least in part, to a failure of sufficient MPZ to reach the cell surface and that this impaired trafficking is associated with deficient serine phosphorylation in the cytoplasmic domain.

Amino Acid Sequence↗
PubMed1995

Widespread expression of the peripheral myelin protein-22 gene (PMP22) in neural and non-neural tissues during murine development.

The gene encoding the peripheral myelin protein PMP22 is affected by various mutations in the hereditary peripheral neuropathies Charcot-Marie-Tooth disease type 1A (CMT1A), Déjérine-Sottas syndrome (DSS) and hereditary neuropathy with liability to pressure palsies (HNPP). In contrast to the recent remarkable progress in the genetics of the PMP22 gene, the biological function of PMP22 remains largely unknown. In this report, we have confirmed by using in situ hybridization techniques that high levels of PMP22 mRNA are present in maturing peripheral nerves of the 2-week-old mouse, a finding consistent with the PNS-specific defect observed in hereditary peripheral neuropathies. However, high levels of PMP22 transcripts were also found in the villi of the adult gut, and PMP22 expression was detected in various non-neural tissues during embryonic mouse development. In early embryogenesis (9.5 days postconception, dpc), PMP22 RNA expression appears restricted to the epithelial ectodermal layer. During early organogenesis (11.5 dpc), particularly high levels of expression are present in the capsule surrounding the liver and in the forming gut, while low levels of PMP22 mRNA can be found in precartilagous condensations forming the vertebrae and the ventricular layer of the myelencephalon. During midgestation development (14.5 dpc to 16.5 dpc), the number of PMP22-positive tissues increases, and high expression is detected in several mesoderm-derived tissues, in particular connective tissues of the face region, bones including the vertebrae, the lung mesenchym, and in muscles. In addition, high expression is also found in ectoderm-derived tissues, especially the epithelia of the lens and the skin. These findings strongly suggest that PMP22 serves not only a PNS-specific function but is also of broader biological significance in cell proliferation and/or differentiation.

Age Factors↗
PubMed1995

Developmental defects of teeth in survivors of childhood ALL are related to the therapy and age at diagnosis.

The relation of the therapy used and age at diagnosis to developmental defects of dental enamel and root was analyzed in 45 survivors of childhood acute lymphoblastic leukemia (ALL) and compared to that of age- and sex-matched healthy controls. Chemotherapy alone increased the number of enamel defects, but it did not affect the roots. The scattered irradiation of 0.72-1.44 Gy to the dental arches during central nervous system (CNS) irradiation caused an increased number of developmental defects both in enamel and root. Age at diagnosis is an important factor and it showed that the irradiation of 10 Gy did not cause enamel defects if amelogenesis was complete. In conclusion, the therapy is related to developmental defects of the teeth but the most important factor is age, both at diagnosis and during the therapy.

Adolescent↗
PubMed2004

Threshold electrotonus in chronic inflammatory demyelinating polyneuropathy: correlation with clinical profiles.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is characterized by multifocal demyelination along the course of the nerves, and involvement of the intermediate segments may correlate with more severe demyelination associated with breakdown of the blood-nerve barrier. Threshold electrotonus was used to study whether altered membrane properties of the median nerve at the wrist (intermediate segment) are associated with clinical profiles in 21 CIDP patients. In response to hyperpolarizing conditioning stimuli, the threshold changes were significantly greater for CIDP patients than for normal controls (n = 49). The pattern was similar to that of 11 patients with Charcot-Marie-Tooth disease type 1a, who exhibited abnormally high thresholds to hyperpolarizing currents. The abnormal threshold electrotonus was present in 48% of the CIDP patients and was associated with longer disease duration, more severe disability, poorer response to immune treatments, and slower nerve conduction velocities. Threshold electrotonus can be used to detect demyelination at the tested sites and may provide new information about pathophysiology and distribution patterns of demyelination in CIDP.

Action Potentials↗
PubMed2004

Multifocal slowing of nerve conduction in metachromatic leukodystrophy.

Polyneuropathy is invariably associated with the late-infantile form of metachromatic leukodystrophy (MLD), and occurs frequently in the early juvenile, juvenile, and adult variants. Uniform slowing of nerve conduction velocity is the neurophysiologic hallmark of metachromatic leukodystrophy and other inherited demyelinating polyneuropathies. To evaluate the consistency of this principle, we reviewed nerve conduction studies in 9 children with late-infantile or early-juvenile metachromatic leukodystrophy. Each child had significant slowing of motor nerve conduction velocity (NCV). The compound muscle action potentials showed abnormal temporal dispersion in 3 of the 9 children, which is usually regarded as the hallmark of acquired demyelinating polyneuropathies. There are reports of multifocal slowing in other hereditary processes including X-linked Charcot-Marie-Tooth disease, hereditary neuropathy with liability to pressure palsies, and adrenomyeloneuropathy. Although multifocal NCV slowing in a child with polyneuropathy is seen most commonly in acquired conditions, a hereditary process, including MLD, cannot always be excluded in this setting.

Action Potentials↗
PubMed2006

Dispersion of compound muscle action potential in hereditary neuropathies and chronic inflammatory demyelinating polyneuropathy.

Distal compound muscle action potential (DCMAP) dispersion, defined as a DCMAP duration > or = 9 ms, and proximal-distal (P-D) CMAP dispersion are considered useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). Distal and P-D CMAP dispersion have not been fully studied in hereditary neuropathies, and it is not known whether these measures distinguish hereditary from acquired demyelination. We compared DCMAP duration and P-D CMAP dispersion in 91 genetically characterized hereditary neuropathies and 33 subjects with CIDP. DCMAP dispersion was more frequent in nerves affected by CIDP (41.5%) than in Charcot-Marie-Tooth disease (CMT)1A (24.4%), CMT1B (7.4%), hereditary neuropathy with liability to pressure palsies (HNPP) (10.5%), or CMTX (9.8%). P-D CMAP dispersion was more frequent in CIDP (27.7% of nerves) than in hereditary neuropathies (16.3%) when applying American Academy of Neurology (AAN) criteria; however, its frequency was similar in CIDP and the hereditary neuropathies using the more restrictive criteria of the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). Although dispersion is more common in CIDP than in the hereditary neuropathies, DCMAP and P-D dispersion occur in at least one motor nerve in a significant proportion of hereditary neuropathies, and cannot be used in isolation to distinguish acquired from hereditary demyelination.

Action Potentials↗
PubMedDate not supplied

Acquired versus familial demyelinative neuropathies in children.

The electrophysiologic differences between chronic acquired demyelinative neuropathy and the demyelinative form of Charcot-Marie-Tooth disease have recently been reported. The present report extends these observations to include the genetically determined demyelinating neuropathies seen in metachromatic leukodystrophy, Krabbe's leukodystrophy, and Cockayne's syndrome. The electrophysiologic features of metachromatic leukodystrophy (five patients), Krabbe's (four patients), and Cockayne's syndrome (three patients) were all similar. There was uniform slowing of conduction (both in different nerves and in different nerve segments), and conduction block was not seen. These findings are consistent with a uniform degree of demyelination in multiple nerves and throughout the entire length of individual axons. Thus, uniform slowing of nerve conduction constitutes strong evidence for a familial demyelinative neuropathy, as opposed to the multifocal slowing seen in acute and chronic acquired demyelinative neuropathy.

Adolescent↗