A novel de novo NIPA1 missense mutation associated to hereditary spastic paraplegia

SPG6 accounts for 1% of autosomal dominant Hereditary Spastic Paraplegia (HSP) and is caused by pathogenic variants in NIPA1, which encodes a magnesium transporter located in plasma membrane and early endosomes, implicated in neuronal development and maintenance. Here we report a 39-year-old woman affected by progressive gait disturbance associated to absence seizures episodes within childhood. Clinical exome sequencing identified a likely pathogenic de novo heterozygous variant in NIPA1 (NM_144599.5 c.249 C > G; p.Asn83Lys). Molecular modelling was performed to evaluate putative functional consequence of the NIPA1 protein. Indeed, the Asn83Lys modification is predicted to induce a significant perturbation of the protein structure, altering signal transduction or small-molecule transport by modulating the length of the second transmembrane domain. This is the first study reporting a SPG6-affected patient harbouring the NIPA1 p.Asn83Lys mutation.