FUS-NLS mutation causes neurodevelopmental and systemic metabolic alterations.

Mutations in the ubiquitously expressed DNA/RNA binding protein FUS cause aggressive juvenile forms of amyotrophic lateral sclerosis (ALS). While most FUS mutation studies have focused on motor neuron degeneration, little is known about wider systemic or developmental effects. We studied pleiotropic phenotypes in a physiological knock-in mouse model carrying the pathogenic FUSDelta14 mutation in homozygosity. RNA sequencing of multiple organs aimed to identify pathways altered by the mutant protein in the systemic transcriptome, including metabolic tissues given the link between ALS-FTD and altered metabolism. Few genes were commonly altered across all tissues, and most genes and pathways affected were generally tissue-specific. Phenotypic assessment of mice revealed systemic metabolic alterations related to the pathway changes identified. MRI brain scans and histological characterisation revealed that homozygous FUSDelta14 brains were smaller and displayed significant morphological alterations including a thinner cortex, reduced neuronal number and increased gliosis, which correlated with early cognitive impairment and fatal seizures. We show that the disease aetiology of FUS mutations can include both neurodevelopmental and systemic alterations.