ABSTRACT
The diagnostic gap for rare neurodegenerative diseases is still considerable, despite continuous advances in gene identification. Many novel Mendelian genes have only been identified in a few families worldwide. Here we report the identification of an autosomal-dominant gene for hereditary spastic paraplegia (HSP) in 10 families that are of diverse geographic origin and whose affected members all carry unique truncating changes in a circumscript region of UBAP1 (ubiquitin-associated protein 1). HSP is a neurodegenerative disease characterized by progressive lower-limb spasticity and weakness, as well as frequent bladder dysfunction. At least 40% of affected persons are currently undiagnosed after exome sequencing. We identified pathological truncating variants in UBAP1 in affected persons from Iran, USA, Germany, Canada, Spain, and Bulgarian Roma. The genetic support ranges from linkage in the largest family (LOD = 8.3) to three confirmed de novo mutations. We show that mRNA in the fibroblasts of affected individuals escapes nonsense-mediated decay and thus leads to the expression of truncated proteins; in addition, concentrations of the full-length protein are reduced in comparison to those in controls. This suggests either a dominant-negative effect or haploinsufficiency. UBAP1 links endosomal trafficking to the ubiquitination machinery pathways that have been previously implicated in HSPs, and UBAP1 provides a bridge toward a more unified pathophysiology.
Subject(s)
Carrier Proteins/genetics , Mutation , Spastic Paraplegia, Hereditary/genetics , Adolescent , Adult , Aged , Aged, 80 and over , Animals , Child , Child, Preschool , Databases, Factual , Disease Models, Animal , Endosomes/metabolism , Family Health , Female , Fibroblasts/metabolism , Genes, Dominant , Genetic Linkage , Genetic Predisposition to Disease , Genomics , HEK293 Cells , Haploinsufficiency , Humans , Male , Middle Aged , Pedigree , Protein Isoforms , Young Adult , ZebrafishABSTRACT
The fluorescence microscopy-based detection of intracellular LC3, p62, and/or WIPI punctate structures is a robust tool to monitor and assess macroautophagy/autophagy in single cells. This method was established for automated high-throughput/content analysis to reliably detect narrow differences in autophagy activity/capacity and to provide screening opportunities for biological and chemical libraries.
Subject(s)
Autophagy/physiology , High-Throughput Screening Assays/methods , Image Processing, Computer-Assisted/methods , Single-Cell Analysis/methods , Autophagy-Related Proteins/metabolism , Cell Culture Techniques/instrumentation , Cell Culture Techniques/methods , Cell Line , High-Throughput Screening Assays/instrumentation , Humans , Image Processing, Computer-Assisted/instrumentation , Microscopy, Confocal/instrumentation , Microscopy, Confocal/methods , Microscopy, Fluorescence/instrumentation , Microscopy, Fluorescence/methods , Microtubule-Associated Proteins/metabolism , Single-Cell Analysis/instrumentationABSTRACT
The article discusses new findings on the role of the 4 human WIPI proteins at the onset of macroautophagy/autophagy. New insights revealing a circuit scaffold function of WIPI ß-propellers that interconnect autophagy signaling control with appropriate autophagosome formation are summarized.
