A cellular assay to determine the fusion capacity of MFN2 variants linked to Charcot-Marie-Tooth type 2A

Abstract

Charcot-Marie-Tooth Disease (CMT) is an inherited peripheral neuropathy with two main forms: demyelinating CMT1 and axonal CMT2. The most frequent subtype of CMT2 (CMT2A) is linked to mutations of MFN2, encoding a membrane-anchored GTP-binding protein essential for mitochondrial outer membrane fusion. The use of Next-Generation Sequencing for genetic analysis has led to the identification of increasing numbers of MFN2 variants, but a majority of them remain variants of unknown significance, depriving patients of a clear diagnosis. In this work, we establish a cellular assay allowing to assess the impact of MFN2 variants linked to CMT2A on the fusion capacity of MFN2. The analysis of 12 MFN2 variants revealed that five abolish fusion, one induces an important reduction and six retain a fusion capacity similar to that of wild-type MFN2. Their analysis with computational variant effect predictors demonstrated a remarkable correlation of our results with predictions based on protein sequence analysis. This work develops novel tools to determine the functional impact of known and novel MFN2 variants and identifies computational tools allowing to predict their possible consequences and pathogenicity.