SPG15 is a recessively inherited HSP variant caused by mutations in the ZFYVE26 gene and is additionally characterized by cerebellar ataxia, mental decline, and progressive thinning of the corpus callosum.
We studied in more detail the SPG5-related spectrum of complex phenotypes by screening CYPB1 for mutations in a large cohort of 105 Italian hereditary spastic paraplegias (HSPs) index patients including 50 patients with a complicated HSP (cHSP) phenotype overlapping the SPG11- and the SPG15-related forms except for the lack of thin corpus callosum and 55 pure patients.
We show that the gene KIAA0415 encodes a putative helicase that interacts with SPG11 and SPG15, two proteins mutated in hereditary spastic paraplegia (HSP).
A sample of 36 index patients with early onset complicated HSP and a family history compatible with autosomal recessive inheritance was collected and screened for mutations in SPG11 and SPG15.
Taking into account previously published results and new data generated in this work, genetic studies revealed significant or putative linkage to known HSP loci in 13 families (34.2%) to either SPG11 (7/38, 18.4%), SPG15 (4/38, 10.5%) or to SPG4 and SPG5 in one family each.
The locus designated spastic paraplegia 15 (SPG15), located in a 16-Mb interval on chromosome 14q, is associated with a rare autosomal recessive complicated form of HSP known as Kjellin's syndrome.
Haplotype construction of nearby markers confirms the existence of this novel HSP locus (SPG15) and narrows it to a 19-cM interval flanked by D14S1038 and D14S61.