Preferential expression of the maternally inherited X-linked phosphoglycerate kinase allele in human erythrocytes

Abstract

The stability of allelic gene expression of X-linked phosphoglycerate kinase was studied in seven carriers of a rare genetic variant named PGK München. The enzymatic activities in erythrocytes of five heterozygous females and three hemizygous males were determined repeatedly over a period of 10 years (1975-1984) and shown to remain constant. As the phosphoglycerate kinase activity is lower in cells expressing the PGK München allele, the ratio of the two cell types in all heterozygous females of the PGK München kindred could be calculated from the PGK activity and from the known allozyme activities in erythrocytes of homozygous wild type or hemizygous PGK München carriers. Since the maternal or paternal origin of both alleles is known from the pedigree, the quantitative expression of the maternally derived allozyme in heterozygous women could be determined. In heterozygous carriers the cell pool expressing the maternally inherited allele was significantly increased, independently, of the PGK allele linked to the maternal X chromosome (P less than 0.001). Our data show that inactivation of one of the two X chromosomes in human female erythropoietic stem cell precursors may be non-random, at least in the kindred and cell populations described here. The results are discussed in the context of random X chromosome inactivation (Lyon hypothesis).

Parental influences on expression of glucose-6-phosphate dehydrogenase,G6pd, in the mouse; a case of imprinting

“…As reported by Krietsch et al (1985) for phosphoglycerate kinase in man, this can be done from the known specific activity of the enzyme in homozygotes or hemizygotes for the normal and mutant alleles. In order to facilitate comparison between earlier results and those obtained in the present study, the proportion of activity due to the a-m allele has been calculated for each cross, at both ages tested.…”