A Novel Mutation of GARS in a Chinese Family With Distal Hereditary Motor Neuropathy Type V

Glycyl-tRNA synthetase (GARS) gene mutations have been reported to be associated with Charcot-Marie-Tooth disease 2D and distal hereditary motor neuropathy type V (dHMN-V). In this study, we report a novel GARS mutation in a Chinese family with dHMN-V. Clinical, electromyogram, genetic, and functional data were explored. The proband was an 11-year-old girl presented with progressive distal limb muscle weakness and atrophy due to peripheral motor neuropathy for 1 year. Another five members from three successive generations of the family showed similar symptoms during their first to second decades and demonstrated an autosomal dominant inheritance. The results of genetic testing revealed a novel c.383T>G mutation in the GARS gene in the affected individuals, showing apparent genetic cosegregation. Further bioinformatic analyses showed that the c.383T > G mutation resulted in L128R alteration in the second functional protein domain, and the mutation site was well conserved among different species. In silico analysis predicted that this mutation probably affected protein function. In vitro, this GARS mutation led to a different protein localization pattern than that of the wild-type enzyme. The study found a novel GARS mutation of c.383T > G causing dHMN-V with subcellular localization abnormity in a genetic cosegregation family. These findings broaden the mutational spectrum of GARS.

REEP1 and REEP2 proteins are preferentially expressed in neuronal and neuronal-like exocytotic tissues

The six members of the Receptor Expression Enhancing Protein (REEP) family were originally identified based on their ability to enhance heterologous expression of olfactory receptors and other difficult to express G protein-coupled receptors. Interestingly, REEP1 mutations have been linked to neurodegenerative disorders of upper and lower motor neurons, hereditary spastic paraplegia (HSP) and distal hereditary motor neuropathy type V (dHMN-V). The closely related REEP2 isoform has not demonstrated any such disease linkage. Previous research has suggested that REEP1 mRNA is ubiquitously expressed in brain, muscle, endocrine, and multiple other organs, inconsistent with the neurodegenerative phenotype observed in HSP and dHMN-V. To more fully examine REEP1 expression, we developed and characterized a new REEP1 monoclonal antibody for both immunoblotting and immunofluorescent microscopic analysis. Unlike previous RT-PCR studies, immunoblotting demonstrated that REEP1 protein was not ubiquitous; its expression was restricted to neuronal tissues (brain, spinal cord) and testes. Gene expression microarray analysis demonstrated REEP1 and REEP2 mRNA expression in superior cervical and stellate sympathetic ganglia tissue. Furthermore, expression of endogenous REEP1 was confirmed in cultured murine sympathetic ganglion neurons by RT-PCR and immunofluorescent staining, with expression occurring between Day 4 and Day 8 of culture. Lastly, we demonstrated that REEP2 protein expression was also restricted to neuronal tissues (brain and spinal cord) and tissues that exhibit neuronal-like exocytosis (testes, pituitary, and adrenal gland). In addition to sensory tissues, expression of the REEP1/REEP2 subfamily appears to be restricted to neuronal and neuronal-like exocytotic tissues, consistent with neuronally restricted symptoms of REEP1 genetic disorders.