Asynchronous replication of alleles in genomes carrying a microdeletion

Background: While most allelic pairs of DNA replicate synchronously during the S phase of the cell cycle, some genes normally replicate asynchronously, i.e., genes on the X chromosome and imprinted genes. The replication control mechanism is unknown but was shown to be impaired in malignancies and chromosomal trisomies where replication pattern becomes asynchronous. Objectives: To determine the level of asynchronization in replication timing of cells from patients with microdeleted genomes. Methods: We applied monocolor fluorescent in situ hybridization with different probes on leukocytes from microdeleted genomes. Results: All samples derived from the microdeleted genomes showed significantly higher levels of an asynchronized pattern compared to normal individuals. Conclusions: Even a "small" genetic imbalance (microdeletion) can interfere with gene replication and cell cycle progression, as previously shown in full trisomies.