Albee Messing, VMD, PhD

Slide of the Week: Albee Messing

TDP-43 mislocalization in a mouse model of Alexander disease

Legend: Mislocalized TDP-43 colocalizes with GFAP in GfapR236H/+ mice. TDP-43 (red) and GFAP (green) immunolabeling in coronal brain sections from 10-week-old mice. Nuclei are labeled with DAPI (blue). In WT mice, TDP-43 is primarily localized to neuronal nuclei (pyramidal layer of the hippocampus shown here), with very little colocalization with GFAP. In GfapR236H/+mice, TDP-43 is found in cell bodies and proximal processes, and colocalizes with GFAP (arrow).

Citation: Walker AK, Daniels CM, Goldman JE, Trojanowski JQ, Lee VM, Messing A. (2014)  Astrocytic TDP-43 pathology in Alexander disease. Journal of Neuroscience. 2014 May 7;34(19):6448-58.PMID: 24806671

Abstract: Alexander disease (AxD) is a rare neurodegenerative disorder characterized pathologically by the presence of eosinophilic inclusions known as Rosenthal fibers (RFs) within astrocytes, and is caused by dominant mutations in the coding region of the gene encoding glial fibrillary acidic protein (GFAP). GFAP is the major astrocytic intermediate filament, and in AxD patient brain tissue GFAP is a major component of RFs. TAR DNA binding protein of 43 kDa (TDP-43) is the major pathological protein in almost all cases of the neurode- generative disease amyotrophic lateral sclerosis (ALS) and ~50% of frontotemporal lobar degeneration (FTLD), designated as FTLD- TDP. In ALS and FTLD-TDP, TDP-43 becomes insoluble, ubiquitinated, and pathologically phosphorylated and accumulates in cytoplasmic inclusions in both neurons and glia of affected brain and spinal cord regions. Previously, TDP-43 was detected in RFs of human pilocytic astrocytomas; however, involvement of TDP-43 in AxD has not been determined. Here we show that TDP-43 is present in RFs in AxD patient brains, and that insoluble phosphorylated full-length and high molecular weight TDP-43 accumulates in white matter of such brains. Phosphorylated TDP-43 also accumulates in the detergent-insoluble fraction from affected brain regions of GfapR236H/+ knock-in mice, which harbor a GFAP mutation homologous to one that causes AxD in humans, and TDP-43 colocalizes with astrocytic RF pathology in GfapR236H/+ mice and transgenic mice overexpressing human wild-type GFAP. These findings suggest com- mon pathogenic mechanisms in ALS, FTLD, and AxD, and this is the first report of TDP-43 involvement in a neurological disorder primarily affecting astrocytes. PMCID: PMC4012304

About the Lab: Albee Messing’s lab is focused on understanding developmental and pathologic aspects of glial cell biology in the nervous system of the mouse, with a particular focus on astrocytes and their major intermediate filament protein, GFAP. Main strategies involve genetic manipulation of glial gene expression using transgenic techniques, and gene targeting in embryonic stem cells, to generate mutant strains of mice. Current projects address a variety of topics such as regulation of gene expression, the role of GFAP mutations and accumulation in the pathogenesis of Alexander disease. A major effort is devoted to devising novel therapeutic strategies for treatment of this disorder, and identifying biomarkers to permit monitoring severity or progression of the disease.

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