Connexin32 and X-Linked Charcot-Marie-Tooth Disease

This paper deals with the genetic defect responsible for the X-linked form of Charcot-Marie-Tooth disease.Mutations in the gap junction geneconnexin32(Cx32) cause the X-linked form of Charcot–Marie–Tooth disease, an inherited demyelinating neuropathy

Altered Trafficking of Mutant Connexin32

We examined the cellular localization of nine different connexin32 (Cx32) mutants associated with X-linked Charcot–Marie–Tooth disease (CMTX) in communication-incompetent mammalian cells. Cx32 mRNA was made, but little or no protein was detected in one class of mutants. In another class of mutants, Cx32 protein was detectable in the cytoplasm and at the cell surface, where it appeared as plaques and punctate staining. Cx32 immunoreactivity in a third class of mutants was restricted to the cytoplasm, where it often colocalized with the Golgi apparatus. Our studies suggest that CMTX mutations have a predominant effect on the trafficking of Cx32 protein, resulting in a potentially toxic cytoplasmic accumulation of Cx32 in these cells. These results and evidence of cytoplasmic accumulation of other mutated myelin proteins suggest that diseases affecting myelinating cells may share a common pathophysiology

Connexin32 is a Myelin-Related Protein in the PNS and CNS

We have examined the expression of a gap junction protein, connexin32 (Cx32), in Schwann cells and oligodendrocytes. In peripheral nerve, Cx32 is found in the paranodal myelin loops and Schmidt-Lanterman incisures of myelinating Schwann cells, and the levels of Cx32 protein and mRNA change in parallel with those of other myelin-related genes during development, Wallerian degeneration, and axonal regeneration. In the central nervous system, Cx32 is found in oligodendrocytes and their processes, but not in compact myelin, and the levels of Cx32 protein and mRNA increase during development in parallel with those of the other myelin genes. Thus, Cx32 is expressed as part of the myelinating phenotype of both Schwann cells and oligodendrocytes, indicating that this gap junction protein plays in important role in the biology of myelin-forming cells

A novel cell immunoassay to measure survival of motor neurons protein in blood cells

BACKGROUND: The motor neuron degenerative disease spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality and is caused by mutations in the survival of motor neurons (SMN) gene that reduce the expression levels of the SMN protein. A major goal of current therapeutic approaches is to increase SMN levels in SMA patients. The purpose of this study was to develop a reliable assay to measure SMN protein levels from peripheral blood samples. METHODS: We developed a novel cell immunoassay to quantitatively measure SMN levels from peripheral blood mononuclear cells (PBMCs) using a single anti-SMN antibody. RESULTS: SMN levels determined by the cell immunoassay are comparable to levels determined by Western blot, but in contrast, the immunoassay does not involve cell lysis, requires a small amount of patient material, and can be done on a large number of samples simultaneously. SMN levels from PBMCs are not influenced by cell type heterogeneity. CONCLUSION: SMN levels measured from total PBMCs provide an important snapshot of SMN protein expression, which should be a useful aid in SMA diagnosis, and a surrogate marker of efficacy of treatment in SMA clinical trials

Clinical and Molecular Aspects of Senataxin Mutations in Amyotrophic Lateral Sclerosis 4

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154673/1/ana25681_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154673/2/ana25681.pd

Assessing Function and Endurance in Adults with Spinal and Bulbar Muscular Atrophy: Validity of the Adult Myopathy Assessment Tool

Purpose. The adult myopathy assessment tool (AMAT) is a performance-based battery comprised of functional and endurance subscales that can be completed in approximately 30 minutes without the use of specialized equipment. The purpose of this study was to determine the construct validity and internal consistency of the AMAT with a sample of adults with spinal and bulbar muscular atrophy (SBMA). Methods. AMAT validity was assessed in 56-male participants with genetically confirmed SBMA (mean age, 53 ± 10 years). The participants completed the AMAT and assessments for disease status, strength, and functional status. Results. Lower AMAT scores were associated with longer disease duration (r = -0.29; P \u3c 0.03) and lower serum androgen levels (r = 0.49-0.59; P \u3c 0.001). The AMAT was significantly correlated with strength and functional status (r = 0.82-0.88; P \u3c 0.001). The domains of the AMAT exhibited good internal consistency (Cronbach\u27s α  = 0.77-0.89; P \u3c 0.001). Conclusions. The AMAT is a standardized, performance-based tool that may be used to assess functional limitations and muscle endurance. The AMAT has good internal consistency, and the construct validity of the AMAT is supported by its significant associations with hormonal, strength, and functional characteristics of adults with SBMA. This trial is registered with Clinicaltrials.gov identifier NCT00303446

Exome Sequencing Identifies a Novel TRPV4 Mutation in a CMT2C Family

Molecular and Cellular Biolog

A motor neuron disease–associated mutation in p150Glued perturbs dynactin function and induces protein aggregation

The microtubule motor cytoplasmic dynein and its activator dynactin drive vesicular transport and mitotic spindle organization. Dynactin is ubiquitously expressed in eukaryotes, but a G59S mutation in the p150Glued subunit of dynactin results in the specific degeneration of motor neurons. This mutation in the conserved cytoskeleton-associated protein, glycine-rich (CAP-Gly) domain lowers the affinity of p150Glued for microtubules and EB1. Cell lines from patients are morphologically normal but show delayed recovery after nocodazole treatment, consistent with a subtle disruption of dynein/dynactin function. The G59S mutation disrupts the folding of the CAP-Gly domain, resulting in aggregation of the p150Glued protein both in vitro and in vivo, which is accompanied by an increase in cell death in a motor neuron cell line. Overexpression of the chaperone Hsp70 inhibits aggregate formation and prevents cell death. These data support a model in which a point mutation in p150Glued causes both loss of dynein/dynactin function and gain of toxic function, which together lead to motor neuron cell death