Detection of Fabry's disease heterozygotes by enzyme analysis in single fibroblasts after cell sorting

Single cells were sorted from cultured fibroblasts of five carriers of Fabry's disease using a cell sorter (FACS II). The alpha-galactosidase A activity in the single fibroblasts was assayed in nanoliter droplets with the help of quantitative microfluorimetric techniques. Two populations of fibroblasts were present in the carriers, one showing an alpha-galactosidase-A activity comparable to that of Fabry patients, and another with normal alpha-galactosidase-A activity. This provides evidence of X-inactivation at the alpha-galactosidase-A locus. Since X-inactivation occurs at random, a high number of single cells has to be assayed to increase the clinical reliability for carrier detection. The methodology as presented enables such an approach.