Objective: To identify the genetic defect for adult-onset primary lateral sclerosis (PLS) in a family with 5 patients.
Methods: Whole-exome sequencing was performed to identify the shared genetic variants in 3 affected members in a PLS family with 5 affected individuals. Sanger sequencing was used for validation of the variants and for cosegregation analysis. Mitochondrial activity for both patients and unaffected siblings was measured using a SeaHorse metabolic analyzer.
Results: Whole-exome sequencing and subsequent cosegregation analysis demonstrated that compound heterozygous missense variants L695P and I743T in SPG7 were the only mutations cosegregating with the disease in an autosomal recessive fashion in this family. The parents and siblings are genetically heterozygous and clinically unaffected. Functional studies suggested that the PLS-associated SPG7 mutants affect mitochondrial function when glucose is reduced.
Conclusions: Compound heterozygote mutations in SPG7 are associated with adult-onset PLS, extending the spectrum of SPG7-linked neurologic diseases. Patients with the PLS phenotype should have genetic testing for paraplegin, especially when the condition is familial.