Replication of X chromosomes in complete moles.

DNA replication patterns of X chromosomes in complete hydatidiform moles were studied using cultured fibroblasts from three 46,XX moles resulting from duplication of a haploid sperm, and from a 46,XY mole originating from dispermy. Control cultures included skin fibroblasts from an adult woman and a female fetus as well as PB lymphocytes from an adult woman. Cultures were treated with 5-bromo-deoxyuridine for the last 2-4 h of the S phase, and the chromosome slides prepared were stained by the Hoechst 33258-Giemsa procedure. Each of the three XX moles studied revealed one early-replicating and one late-replicating X chromosomes, while the XY mole revealed one early-replicating X chromosomes. DNA replication patterns of molar X chromosomes were similar to those of adult and fetal fibroblasts, but different from those in adult lymphocytes. These findings indicate that DNA replication kinetics of molar fibroblasts are tissue-specific rather than origin- or developmental-stage specific.