[Identification of SPAST gene variant in a pedigree affected with hereditary spastic paraplegia type 4]

To explore the genetic basis for a pedigree affected with hereditary spastic paraplegia type 4 (HSP4).

Peripheral venous blood samples were taken from members of the four-generation pedigree and 50 healthy controls for the extraction of genomic DNA. Genes associated with peripheral neuropathy and hereditary spastic paraplegia were captured and subjected to targeted capture and next-generation sequencing. The results were confirmed by Sanger sequencing.

DNA sequencing suggested that the proband has carried a heterozygous c.1196C>G variant in exon 9 of the SPAST gene, which can cause substitution of serine by threonine at position 399 (p.Ser399Trp) and lead to change in the protein function. The same variant was also detected in other patients from the pedigree but not among unaffected individuals or the 50 healthy controls. Based on the ACMG 2015 guidelines, the variant was predicted to be possibly pathogenic.

The c.1196C>G variant of the SPAST gene probably underlay the HSP4 in this pedigree.