X inactivation and somatic cell selection rescue female mice carrying a Piga-null mutation.
A somatic mutation in the X linked PIGA gene is responsible for the deficiency of glycosyl phosphatidylinositol (GPI)-anchored proteins on blood cells from patients with paroxysmal nocturnal hemoglobinuria. No inherited form of GPI-anchor deficiency has been described. Because conventional Piga gene knockout is associated with high embryonic lethality in chimeric mice, we used the Cre/loxP system. We generated mice in which two loxP sites flank part of Piga exon 2. After crossbreeding with female mice of the EIIa-cre strain, the floxed allele undergoes Cre-mediated recombination with high efficiency during early embryonic development. Because of X chromosome inactivation, female offspring are mosaic for cells that express or lack GPI-linked proteins. Analysis of mosaic mice showed that in heart, lung, kidney, brain, and liver, mainly wild-type Piga is active, suggesting that these tissues require GPI-linked proteins. The salient exceptions were spleen, thymus, and red blood cells, which had almost equal numbers of cells expressing the wild-type or the recombined allele, implying that GPI-linked proteins are not essential for the derivation of these tissues. PIGA(-) cells had no growth advantage, suggesting that other factors are needed for their clonal dominance in patients with paroxysmal nocturnal hemoglobinuria.
Keller
P
P
Division of Hematology, Departments of Internal Medicine and Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Tremml
G
G
Rosti
V
V
Bessler
M
M
D000818:Animals; D004303:Dosage Compensation, Genetic; D005260:Female; D017353:Gene Deletion; D005786:Gene Expression Regulation; D017261:Glycosylphosphatidylinositols / Q000235:genetics; D006457:Hemoglobinuria, Paroxysmal / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D009928:Organ Specificity
D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; C080086:phosphatidylinositol glycan-class A protein