Affects cell architecture
TFG mutation shown to alter cell structure and cause collapse of the endoplasmic reticulum.
Hereditary spastic paraplegias are a clinically and genetically heterogeneous group of gait disorders. Their pathological hallmark is a length-dependent distal axonopathy of nerve fibers in the corticospinal tract. Involvement of other neurons can cause additional neurological symptoms, which define a diverse set of complex hereditary spastic paraplegias.
We present two siblings who have the unusual combination of early-onset spastic paraplegia, optic atrophy, and neuropathy. Genome-wide SNP-typing, linkage analysis, and exome sequencing revealed a homozygous c.316C>T (p.R106C) variant in the Trk-fused gene (TFG) as the only plausible mutation. Biochemical characterization of the mutant protein demonstrated a defect in its ability to self-assemble into an oligomeric complex, which is critical for normal TFG function. In cell lines, TFG inhibition slows protein secretion from the endoplasmic reticulum (ER) and alters ER morphology, disrupting organization of peripheral ER tubules and causing collapse of the ER network onto the underlying microtubule cytoskeleton.
The present study provides a unique link between altered ER architecture and neurodegeneration.
SOURCE: Proc Natl Acad Sci U S A. 2013 Mar 26;110(13):5091-6. doi: 10.1073/pnas.1217197110. Epub 2013 Mar 11. PMID: 23479643 [PubMed – indexed for MEDLINE] PMCID: PMC3612678 [Available on 2013/9/26]
Inhibition of TFG function causes hereditary axon degeneration by impairing endoplasmic reticulum structure.
Beetz C, Johnson A, Schuh AL, Thakur S, Varga RE, Fothergill T, Hertel N, Bomba-Warczak E, Thiele H, Nürnberg G, Altmüller J, Saxena R, Chapman ER, Dent EW, Nürnberg P, Audhya A.
Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, 07747 Jena, Germany.