Phosphofructokinase activity in fibroblasts aneuploid for chromosome 21.

[monosomy 21]

Although the gene for the liver type (L ) subunit of phosphofructokinase (PFK ) is located on human chromosome 21 and PFKL subunits predominate in fibroblasts , an increase in PFK activity has not been reported in trisomy 21 fibroblasts . However , using well-matched pairs of trisomy 21 and diploid fibroblast strains , we observed an almost 1 .5 -fold increase in mean PFK activity of trisomic cells . In monosomy 21 fibroblasts we found an almost 0 .5 -fold decrease in mean PFK activity . Thus there appears to be a gene -dosage effect for the PFKL gene , as for other loci on chromosome 21 . PFK activity in a cell strain deleted for the distal part of band 21 q 22 .3 was not decreased , suggesting with other data that PFKL is located in the midportion of band 21 q 22 .3 .