A refined physical and transcriptional map of the SPG9 locus on 10q23.3-q24.2

Hereditary spastic paraplegia (HSP) is a genetically heterogeneous disorder characterised by progressive spasticity of the lower limbs. Beside 'pure' forms of HSP, 'complicated' forms are reported, where spasticity occurs ass ociated with additional symptoms. We recently described an Italian family w ith a complicated dominant form of HSP (SPG9) and we mapped the gene respon sible to 10q23.3-q24.2, in a 12 cM interval between markers D10S564 and D10 S603. The phenotypic manifestations in our family are reminiscent of those already described in a smaller British pedigree. We typed individuals from this British family using markers located in the SPG9 critical interval and haplotype reconstruction showed the disorder co-segregating with SPG9. To characterise the SPG9 region better, we constructed a contig of 22 YACs, as signed it to 18 polymorphic markers and positioned 54 ESTs. Furthermore, we searched for ESTs containing a trinucleotide repeat sequence, since antici pation of symptoms was reported in both families. Finally, analysis of a mu scle biopsy specimen from one patient was normal, suggesting that, contrary to SPG7, mitochondrial disturbance could not be a primary feature of SPG9.