A novel loss of function mutation in adaptor protein complex 4, subunit mu-1 causing autosomal recessive spastic paraplegia 50.

Insertion of these eight nucleotides in the AP4M1 gene is predicted to result in a premature protein product of 132 amino acids. The truncated protein product lacks a signal binding domain which is essential for protein-protein interactions and the transport of cargo proteins to the membrane. Thus, the identified variant is pathogenic and our study expands the knowledge of clinical and genetic features of SPG50.