ALS mutations do not alter perineuronal net formation in human stem cell-derived motor neurons
Perineuronal nets (PNNs) are extracellular matrix structures that stabilise synaptic inputs and regulate neuronal plasticity. Although PNN dysregulation is observed in several neurological disorders, their relevance to amyotrophic lateral sclerosis (ALS) remains unclear. In particular, the extent to which PNN alterations in ALS are motor neuron (MN)-intrinsic is unknown. We investigated whether human pluripotent stem cell-derived MNs form PNN-like structures in vitro, and whether ALS-associated mutations alter this process. We show that MNs generate PNN-like structures containing hyaluronan, tenascin-R, and aggrecan and that their formation and gene expression were not altered by ALS mutations. To explore whether PNN dysregulation reflects contributions from other cell types or selective MN vulnerability, we conducted meta-analyses of transcriptomic datasets from pluripotent stem cell-derived astrocytes carrying ALS-associated mutations, as well as datasets comparing MN populations with differential susceptibility to ALS. These analyses revealed no consistent differences in PNN-related gene expression in human stem cell-derived MN. In contrast, transcriptomic analyses of human post-mortem ALS tissues revealed significant dysregulation of PNN-related genes, including core PNN components and linker proteins. These findings suggest that PNN changes in ALS are not MN-intrinsic, but may result from interactions with other cell types in the central nervous system such as glia.