Laboratory analysis showed that the disorder was not caused by mutations in genes that cause SCA-1, SCA-2, SCA-3, SCA-6, SCA-7, SCA-8, and SCA-12; not linked to other known loci for autosomal dominant ataxia (SCA-4, SCA-5, SCA-10, SCA-11, SCA-13, SCA-14, and SCA-16); and not linked to known loci for autosomal dominant hereditary spastic paraplegia (HSP) (SPG-3, SPG-4, SPG-6, SPG-8, SPG-9, SPG-10, SPG-12, and SPG-13) or autosomal recessive HSP SPG-7.
The negative result obtained in 15 patients without mutations in SPG4 in whom 4 other genes were analyzed (SPG3A, SPG6, SPG10, and SPG13) indicate that these genes are not frequently mutated in sporadic pure HSP.
The disease locus was mapped to a region on chromosome 2q 24-31, flanked by markers rs1424937-rs1559510, proximal to SPG13, in a region where there are no known HSP or DYT genes.
A prominent diversity in HSPs expression was also exhibited in the foragers at 45 °C with one HSP (Hsp70) in <i>A. m. jemenitica</i>, two HSPs (Hsp40 and Hsp70) in <i>A. m. carnica</i>, and three HSPs (Hsp40, Hsp60 and Hsp70) in <i>A. m. ligustica</i>.