A physical map of the 6q14-q15 region harboring the locus for the lysosomal membrane sialic acid transport defect.

Two phenotypic presentations of excessive accumulation of free sialic acid in lysosomes, Salla disease and infantile sialic acid storage disease, have been assigned to the same locus at 6q14-q15. Here we have restricted the critical DNA region by analyses of extended haplotypes and constructed a long-range physical contig over the critical 200-kb chromosomal region flanked by the markers D6S280 and D6S1622. The efficient fiber-FISH technique was applied to order and orient the clones, and this facilitated avoidance of the tedious restriction mapping by pulsed-field gel electrophoresis. We excluded all seven known ESTs and nine cDNAs assigned to this DNA region and tentatively identified two potential CpG islands within the region, which now represent positional candidate genes for the sialic acid storage disorders.