Biology subjects

Iwabuchi, S.

Publications and source records attributed to Iwabuchi, S..

3 recordsLinked to original sources

bioRxiv2019

Localization of the signal of dystonia-associated protein torsinA near the Golgi apparatus in cultured central neurons

A single in-frame deletion of a codon for a glutamic acid residue within the TOR1A gene is linked to the autosomal-dominant movement disorder DYT1 dystonia, a condition characterized by involuntary muscle contractions that cause abnormal posture. This gene encodes the protein torsinA, and the functions of both wild-type and mutant ({Delta}E-torsinA) forms remain poorly understood. Previous studies based on overexpression systems indicated that wild-type torsinA resides mainly in the endoplasmic reticulum but that {Delta}E-torsinA is localized to the nuclear envelope or intracellular inclusions. This mutation-associated mis-localization has been proposed to underlie at least a part of the pathophysiology of DYT1 dystonia. However, the subcellular localization of torsinA has not been extensively studied when expressed at the endogenous level. Here we report an immunocytochemical analysis of torsinA proteins in cultured mouse neurons from a {Delta}E-torsinA knock-in model of DYT1 dystonia, where torsinA proteins are not upregulated. In all examined neurons of wild-type, heterozygous and homozygous mice, torsinA signal was found mainly near the Golgi apparatus, and only weakly in the endoplasmic reticulum and nuclear envelope. These results suggest that, in the absence of overexpression, torsinA proteins are localized near the Golgi apparatus and may influence cellular function involving the organelle.

neuroscience↗

bioRxiv2019

Localization of immunoreactive, dystonia-associated protein torsinA near the Golgi apparatus of cultured rodent astrocytes

An in-frame deletion of a single glutamic acid codon in the TOR1A gene causes the neurological disorder DYT1 dystonia, but the cellular pathophysiology of this disorder remains elusive. A current model postulates that the wild-type (WT) torsinA protein is mainly localized to the endoplasmic reticulum (ER), but that the mutant form ({Delta}E-torsinA) is diverted to the nuclear envelope and cytoplasmic inclusion bodies. This mis-localization has been observed by overexpressing the proteins in neuronal and non-neuronal cells. However, it is not clear whether this model is valid for the astrocytic glial cells that support and modify neuronal functions. Here we report, using rodent astrocytes in primary culture, that the overexpressed torsinA proteins were distributed as predicted by the mis-localization model. We also found by immunocytochemistry that the cultured astrocytes express torsinA endogenously. Most of the signals from endogenous protein, whether the WT or {Delta}E form, were localized near a cis-Golgi marker GM130. Such localization of endogenous proteins was found in glial cells from several sources: the hippocampus of WT rats, the hippocampus and striatum of WT mice, and the hippocampus and striatum of {Delta}E-torsinA knock-in mice, a model of DYT1 dystonia. These results show that the mis-localization model is applicable to overexpressed torsinA proteins, but not applicable to those expressed at endogenous levels, at least in cultured rodent astrocytes. These discrepancies in the distribution of overexpressed versus endogenous torsinA proteins highlight the potential need for caution in interpreting the results of overexpression studies.

neuroscience↗

bioRxiv2019

Transcriptome profiles in brains of mice heterozygous for a DYT1 dystonia-associated mutation in the endogenous Tor1a gene

In patients with the brain disorder dystonia, body movement is severely affected - with involuntary muscle contractions and abnormal postures, causing extensive deterioration of the patients quality of life. The most common inherited form of this disorder is DYT1 dystonia, which is caused by a mutation in TOR1A gene and autosomal dominant. The molecular mechanisms that underlie the effects of the TOR1A mutation on brain function remain unclear. To understand these, we examined the gene expression profiles (transcriptome) in four brain regions (cerebral cortex, hippocampus, striatum and cerebellum) in a mouse model, the heterozygous {Delta}E-torsinA knock-in mice which genetically reproduce the mutation in DYT1 dystonia. The samples were obtained at 2 to 3 weeks of age, a period during which synaptic abnormalities have been reported. Pairwise comparisons of brain regions revealed differential gene expression irrespective of genotype. A comparison of heterozygous to wild-type mice failed to reveal genotype-dependent differences in gene expression in any of the four brain regions when examined individually. However, genotype-dependent differences became apparent when the information for all brain regions was combined. These results suggest that any changes in the transcriptome within a brain region were subtle at this developmental stage, but that statistically significant changes occur across all brain regions. Such changes in the transcriptome, although subtle in degree, could underlie the processes that give rise to DYT1 dystonia.

neuroscience↗