An impaired splicing program underlies differentiation defects in hSOD1^G93A neural progenitor cells

Amyotrophic lateral sclerosis (ALS) is an adult devastating neurodegenerative disease characterized by the loss of upper and lower motor neurons (MNs), resulting in progressive paralysis and death. Genetic animal models of ALS have highlighted dysregulation of synaptic structure and function as a pathogenic feature of ALS-onset and progression. Alternative pre-mRNA splicing (AS), which allows expansion of the coding power of genomes by generating multiple transcript isoforms from each gene, is widely associated with synapse formation and functional specification. Deciphering the link between aberrant splicing regulation and pathogenic features of ALS could pave the ground for novel therapeutic opportunities. Herein, we found that neural progenitor cells (NPCs) derived from the hSOD1^G93A mouse model of ALS displayed increased proliferation and propensity to differentiate into neurons. In parallel, hSOD1^G93A NPCs showed impaired splicing patterns in synaptic genes, which could contribute to the observed phenotype. Remarkably, master splicing regulators of the switch from stemness to neural differentiation are de-regulated in hSOD1^G93A NPCs, thus impacting the differentiation program. Our data indicate that hSOD1^G93A mutation impacts on neurogenesis by increasing the NPC pool in the developing mouse cortex and affecting their intrinsic properties, through the establishment of a specific splicing program.