SPG7 mutations account for less than 5% of hereditary spastic paraplegia (HSP) families.
This is compatible with autosomal recessive inheritance. Cerebellar signs or cerebellar atrophy on brain imaging were the most frequent additional features in patients with SPG7 HSP. Rare nucleotide variants in SPG7 are frequent, complicating routine diagnosis.
BACKGROUND: Mutations in the SPG7 gene, which encodes paraplegin, are responsible for an autosomal recessive hereditary spastic paraplegia (ARHSP).
OBJECTIVE: To screen the SPG7 gene in a large population of HSP families compatible with autosomal recessive transmission.
METHODS: The authors analyzed 136 probands with pure or complex HSP for mutations in the SPG7.
RESULTS: The authors identified 47 variants including 6 mutations, 27 polymorphisms, and 14 changes with unknown effects. In one family from Morocco, compound c.850_851delTTinsC and c.1742_1744delTGG heterozygous mutations were shown to be causative. This family had complex HSP with cerebellar impairment. Progression of the disease was rapid, resulting in a severe disease after 8 years of duration. Also detected were 20 families with one heterozygous mutation that was not found in a large control population. The mutations produced highly defective proteins in four of these families, suggesting that they were probably causative. Direct sequencing of all exons and reverse transcription PCR experiments demonstrated the absence of a second mutation. However, the p.Ala510Val missense substitution previously described as a polymorphism was shown to be significantly associated with HSP, suggesting that it had a functional effect.
Neurology. 2006 Mar 14;66(5):654-9.
Mutation analysis of the paraplegin gene (SPG7) in patients with hereditary spastic paraplegia.
Elleuch N, Depienne C, Benomar A, Hernandez AM, Ferrer X, Fontaine B, Grid D, Tallaksen CM, Zemmouri R, Stevanin G, Durr A, Brice A.
INSERM U679, Neurology and Experimental Therapeutics, Departement de Genetique, Cytogenetique, et Embryologie, Hopital de la Pitie-Salpetriere, Universite Pierre et Marie Curie, Faculte de Medecine, Paris, France.