Autosomal Recessive Hereditary Neuropathy Research Articles

Neuronal degeneration in autonomic nervous system of Dystonia musculorum mice

BackgroundDystonia musculorum (dt) is an autosomal recessive hereditary neuropathy with a characteristic uncoordinated movement and is caused by a defect in the bullous pemphigoid antigen 1 (BPAG1) gene. The neural isoform of BPAG1 is expressed in various neurons, including those in the central and peripheral nerve systems of mice. However, most previous studies on neuronal degeneration in BPAG1-deficient mice focused on peripheral sensory neurons and only limited investigation of the autonomic system has been conducted.MethodsIn this study, patterns of nerve innervation in cutaneous and iridial tissues were examined using general neuronal marker protein gene product 9.5 via immunohistochemistry. To perform quantitative analysis of the autonomic neuronal number, neurons within the lumbar sympathetic and parasympathetic ciliary ganglia were calculated. In addition, autonomic neurons were cultured from embryonic dt/dt mutants to elucidate degenerative patterns in vitro. Distribution patterns of neuronal intermediate filaments in cultured autonomic neurons were thoroughly studied under immunocytochemistry and conventional electron microscopy.ResultsOur immunohistochemistry results indicate that peripheral sensory nerves and autonomic innervation of sweat glands and irises dominated degeneration in dt/dt mice. Quantitative results confirmed that the number of neurons was significantly decreased in the lumbar sympathetic ganglia as well as in the parasympathetic ciliary ganglia of dt/dt mice compared with those of wild-type mice. We also observed that the neuronal intermediate filaments were aggregated abnormally in cultured autonomic neurons from dt/dt embryos.ConclusionsThese results suggest that a deficiency in the cytoskeletal linker BPAG1 is responsible for dominant sensory nerve degeneration and severe autonomic degeneration in dt/dt mice. Additionally, abnormally aggregated neuronal intermediate filaments may participate in neuronal death of cultured autonomic neurons from dt/dt mutants.

Four novel cases of periaxin-related neuropathy and review of the literature

To report 4 cases of autosomal recessive hereditary neuropathy associated with novel mutations in the periaxin gene (PRX) with a review of the literature. Periaxin protein is required for the maintenance of peripheral nerve myelin. Patients with PRX mutations have early-onset autosomal recessive demyelinating Charcot-Marie-Tooth disease (CMT4F) or Déjèrine-Sottas neuropathy (DSN). Only 12 different mutations have been described thus far. Case reports and literature review. Four patients from 3 unrelated families (2 siblings and 2 unrelated patients) were affected by an early-onset, slowly progressive demyelinating neuropathy with relevant sensory involvement. All carried novel frameshift or nonsense mutations in the PRX gene. The 2 siblings were compound heterozygotes for 2 PRX null mutations (p.Q547X and p.K808SfsX2), the third patient harbored a homozygous nonsense mutation (p.E682X), and the last patient had a homozygous 2-nt insertion predicting a premature protein truncation (p.S259PfsX55). Electrophysiologic analysis showed a severe slowing of motor nerve conduction velocities (MNCVs, between 3 and 15.3 m/s) with undetectable sensory nerve action potentials (SNAPs). Sural nerve biopsy, performed in 2 patients, demonstrated a severe demyelinating neuropathy and onion bulb formations. Interestingly, we observed some variability of disease severity within the same family. These cases and review of the literature indicate that PRX-related neuropathies have early onset but overall slow progression. Typical features are prominent sensory involvement, often with sensory ataxia; a moderate-to-dramatic reduction of MNCVs and almost invariable absence of SNAPs; and pathologic demyelination with classic onion bulbs, and less commonly myelin folding and basal lamina onion bulbs.

Mutations in the 5' region of the myotubularin-related protein 2 (MTMR2) gene in autosomal recessive hereditary neuropathy with focally folded myelin.

Focally folded myelin has been recognized as a distinctive feature in some individuals with severe inherited demyelinating neuropathy, with an onset in childhood. Such cases have been shown to be genetically heterogeneous. Alterations in the myotubularin-related protein 2 (MTMR2) gene on chromosome 11q22 have recently been shown to give rise to this phenotype. Mutations have been identified in the 3' region of the MTMR2 gene in four unrelated families, in two of whom the disorder had been mapped to chromosome 11q22 by genetic linkage analysis. We have sequenced the entire coding region and flanking intronic regions of the MTMR2 gene in eight families with early onset autosomal recessive neuropathies. Two novel mutations were identified in exon 4 at the 5' end of the MTMR2 gene in an English and an Indian family. The clinical phenotype and sural nerve pathology in these two families differs in severity, with the proband in the English family having an earlier onset and more severe neuropathy with prominent cranial nerve involvement. This is probably due to mutation type and possible involvement of small nucleotide polymorphisms in phenotype modulation. Detailed sural nerve pathology is presented in both cases. Mutations in the MTMR2 gene are thus an important cause of autosomal recessive demyelinating neuropathy. Identifying further mutations and defining their phenotype will help to clarify the genetic classification of this group of disorders.

Autosomal recessive hereditary neuropathy with focally folded myelin sheaths and linked to chromosome 11q23: a distinct and homogeneous entity

We describe a six generation Saudi kindred, with a recessive hereditary motor and sensory neuropathy (HMSN). Four individuals were affected including two children (a boy and a girl) and a 23-year-old man. The fourth (a female) died at the age of 14 years. Onset of the disease was early (< 2 years) and the clinical and neurophysiological features were, generally, quite similar to those of an Italian family linked to chromosome 11q23. The peculiar pathologic pattern was irregular and redundant loops associated with folding of the myelin sheaths. The genetic study confirmed linkage to chromosome 11q23 and refined the location of the gene between D11S1311 and D11S917, a 3.3 cM region. These findings support the existence of a homogeneous and distinct entity within the form of HMSN associated with focally folded myelin sheaths.