These micronuclei could represent genomic instability during blood production. We therefore examined cells in metaphase obtained directly from the bone marrow of these mice with multiplex fluorescence in situ hybridization (M-FISH). More than 10% of Aldh2−/−Fancd2−/− bone-marrow cells carried chromosomal aberrations, encompassing all classes of cytogenetic change (Fig. 2c–e). These aberrations are not clonal events, because each karyotype was unique (Extended Data Fig. 1).
