Generation of PNH model mice.Piga^flox male mice were crossed with heterozygous or homozygous Cre transgenic female mice.Piga-disrupted female embryos would be heterozygous forPiga disruption and would become mosaic of PIG-A–expressing and PIG-A–nonexpressing cells because of random X-inactivation. Fetal liver cells of 14 days post coitum (d.p.c.) fetuses showing the morphological abnormalities were collected and pooled to transfer to the lethally irradiated C57BL/6 hosts. Shaded cells indicate GPI⁻ fetal liver cells bearing inactivated normal Piga allele (black+) and activated, disrupted-Piga allele (white−). Unshaded cells are GPI⁺ because of inactivation of disrupted-Pigaallele (black−). A portion of fetal liver cells was used for in vitro methylcellulose colony assay along with transplantation. To distinguish donor-derived cells from host-derived cells, mice with the Ly5.1 allele were used for the donors, and those with Ly5.2 were used for the hosts. Floxed indicates Piga allele bearing loxP sites.