Additional homozygous variants were identified, including the risk allele p.Arg261His in NEK1, as well as variants in genes known to be associated with other neurodegenerative diseases, such as HTT (Huntington's disease), ATM (Ataxia-Telangiectasia), and ZFYVE26 (SPG15), and variants in genes previously reported as upregulated (LZTS3) or downregulated (ARMC4, CFAP54, and MTHFSD) in ALS patients.
This provides a mechanistic explanation for why mutations in AP-5/SPG11/SPG15 cause cells to accumulate aberrant endolysosomes, and highlights the role of endosome/lysosome dysfunction in the pathology of hereditary spastic paraplegia and other neurodegenerative disorders.